Discussion:
[darktable-user] white balance
Michael
2017-02-21 21:16:30 UTC
Permalink
is there something where we can take a picture of a gray card and then we
click on it and then dt will adjust all of the colors so that the gray card
is
33-33-33%?

by the way: what is the color of the remaining 1%
--
:-)~MIKE~(-:
I. Ivanov
2017-02-21 21:30:15 UTC
Permalink
Not sure I understand but if you take a picture of a gray card - you can
use the white balance module and in the drop down select custom and then
select from the gray patch that you have taken picture from.

https://www.darktable.org/usermanual/ch03s04.html.php

3.4.1.10. White balance

the drop down of the preset.

Regards,

B
Post by Michael
is there something where we can take a picture of a gray card and then
we click on it and then dt will adjust all of the colors so that the
gray card is
33-33-33%?
by the way: what is the color of the remaining 1%
--
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Marcus Sundman
2017-02-22 00:53:36 UTC
Permalink
Post by Michael
is there something where we can take a picture of a gray card and then
we click on it and then dt will adjust all of the colors so that the
gray card is
33-33-33%?
Usually you use "18% gray" meaning a card that reflects 18% of the light
in the visible spectrum and equal amounts of red, green and blue.

It might actually be nice if the whitebalance module would support
exposure adjustment as well, to make a selected area a specific
brightness, or what do others think?
Post by Michael
by the way: what is the color of the remaining 1%
That "33-33-33%" is your invention, so nobody but you can know what
"remaining 1%" you are talking about. If you were talking about the
reflected % of the individual color channels then there is no "remaining
1%", but the "remaining" (absorbed) amounts of light are 67%, 67% and
67%, respectively.


- Marcus
Michael
2017-02-22 04:21:28 UTC
Permalink
Well, I guess I can try to print a gray card!
Anyone know what the code is for 18% gray? If 18% is right in the middle of
the shades of gray I found one page (
http://www.computerhope.com/cgi-bin/htmlcolor.pl?c=808080) that says the
code is:
808080
and according to the same page it is made up of equal part RGB
*W3C Color Name:* Grey
*RGB:* 128, 128, 128
*HSL:* 0.00, 0.00, 0.50
so what is the authoritative answer?
Post by Michael
is there something where we can take a picture of a gray card and then we
Post by Michael
click on it and then dt will adjust all of the colors so that the gray card
is
33-33-33%?
Usually you use "18% gray" meaning a card that reflects 18% of the light
in the visible spectrum and equal amounts of red, green and blue.
It might actually be nice if the whitebalance module would support
exposure adjustment as well, to make a selected area a specific brightness,
or what do others think?
by the way: what is the color of the remaining 1%
That "33-33-33%" is your invention, so nobody but you can know what
"remaining 1%" you are talking about. If you were talking about the
reflected % of the individual color channels then there is no "remaining
1%", but the "remaining" (absorbed) amounts of light are 67%, 67% and 67%,
respectively.
- Marcus
--
:-)~MIKE~(-:
I. Ivanov
2017-02-22 04:57:18 UTC
Permalink
For the purpose of white balance - I don't think it really matters if it
is 18% or less or more. It is just pure gray. As long as you use a card
and then use it to measure white balance you should be fine.
Post by Michael
Well, I guess I can try to print a gray card!
Anyone know what the code is for 18% gray? If 18% is right in the
middle of the shades of gray I found one page
(http://www.computerhope.com/cgi-bin/htmlcolor.pl?c=808080) that says
808080
and according to the same page it is made up of equal part RGB
*W3C Color Name:* Grey
*RGB:* 128, 128, 128
*HSL:* 0.00, 0.00, 0.50
so what is the authoritative answer?
is there something where we can take a picture of a gray card
and then we click on it and then dt will adjust all of the
colors so that the gray card is
33-33-33%?
Usually you use "18% gray" meaning a card that reflects 18% of the
light in the visible spectrum and equal amounts of red, green and
blue.
It might actually be nice if the whitebalance module would support
exposure adjustment as well, to make a selected area a specific
brightness, or what do others think?
by the way: what is the color of the remaining 1%
That "33-33-33%" is your invention, so nobody but you can know
what "remaining 1%" you are talking about. If you were talking
about the reflected % of the individual color channels then there
is no "remaining 1%", but the "remaining" (absorbed) amounts of
light are 67%, 67% and 67%, respectively.
- Marcus
--
____________________________________________________________________________
darktable user mailing list to unsubscribe send a mail to
Lorenzo Bolzani
2017-02-22 07:36:51 UTC
Permalink
Printing a gray card is a bad idea: you need a very good an perfectly
calibrated printer for this and good non-glossy paper. Otherwise you do not
get perfect gray and you get a random shade of color in all your shots
where you use it. Just buy one.

For white balance, as Ivanov said, any gray is good, actually you typically
use a white card. So *just take a white sheet from the printer a use that.*
I did this in several occasions and works really fine. The minor problem is
that paper is not "perfectly neutral white" but can vary slightly so if you
are looking for ultimate perfection buy a WB card (X-Rite, Opteka, etc.).

The gray 18% thing is about setting the exposure, not the white balance. Of
course you can use the gray card for white balance too but it's not its
main purpose. Typically gray 18 targets are white on the other side for WB.

Often white balance cards came in set of three pieces: white, gray and
black. Almost always the gray here is not gray 18 so it is not good for
exposure reference only for WB.


Bye

Lorenzo
Post by I. Ivanov
For the purpose of white balance - I don't think it really matters if it
is 18% or less or more. It is just pure gray. As long as you use a card and
then use it to measure white balance you should be fine.
Well, I guess I can try to print a gray card!
Anyone know what the code is for 18% gray? If 18% is right in the middle
of the shades of gray I found one page (http://www.computerhope.com/
808080
and according to the same page it is made up of equal part RGB
*W3C Color Name:* Grey
*RGB:* 128, 128, 128
*HSL:* 0.00, 0.00, 0.50
so what is the authoritative answer?
Post by Michael
is there something where we can take a picture of a gray card and then we
Post by Michael
click on it and then dt will adjust all of the colors so that the gray card
is
33-33-33%?
Usually you use "18% gray" meaning a card that reflects 18% of the light
in the visible spectrum and equal amounts of red, green and blue.
It might actually be nice if the whitebalance module would support
exposure adjustment as well, to make a selected area a specific brightness,
or what do others think?
by the way: what is the color of the remaining 1%
That "33-33-33%" is your invention, so nobody but you can know what
"remaining 1%" you are talking about. If you were talking about the
reflected % of the individual color channels then there is no "remaining
1%", but the "remaining" (absorbed) amounts of light are 67%, 67% and 67%,
respectively.
- Marcus
--
____________________________________________________________________________
darktable user mailing list to unsubscribe send a mail to
____________________________________________________________________________
darktable user mailing list to unsubscribe send a mail to
Jean-Luc Coulon (f5ibh)
2017-02-22 09:39:57 UTC
Permalink
Hi,

I think this post is going outside the original question.

The original question was about a grey card and white balance (I I
understood corrrectly).
And what to do if the grey card doesnt appear "neutral" in darktable.

1 - Grey card and white balance.
The fact that the card is 18%, 22% or anything else is unrelevant if we
speak of white balance (the 18% is useful for exposure control... well, I
will no enter the debate about calibration and the various mid-grey,
median-grey or so)
So, yes, we can set the white balance using the "spot" white balance on a
grey card as soon as the grey is neutral.
Neutral means "the same value for red, green, blue".

2 - Card is not neutral
If the grey is not neutral, say a colour cast with one of the channel with
a different value, your white balance will give a colour cast in the
opposite direction.
You can correct that in dt with the module "colour balance" for instance by
selecting the neutral area of interest with the colour picker and trying to
have the same value for all the 3 channels.
But, in my opinion, if your grey card is reasonably neutral, you well not
see (with your eyes) any difference.
A simple sheet of (white) paper can also do the job.

About the reflectivity of the neutral grey : it is an other matter. Such
grey card can be used to adjust the exposure. But as there are strong
controversies about what should be the neutrality of a neutral grey, this
subject is prone to leave to various trolls.

Regards

Jean-Luc
Post by Lorenzo Bolzani
Printing a gray card is a bad idea: you need a very good an perfectly
calibrated printer for this and good non-glossy paper. Otherwise you do not
get perfect gray and you get a random shade of color in all your shots
where you use it. Just buy one.
For white balance, as Ivanov said, any gray is good, actually you
typically use a white card. So *just take a white sheet from the printer
a use that.* I did this in several occasions and works really fine. The
minor problem is that paper is not "perfectly neutral white" but can vary
slightly so if you are looking for ultimate perfection buy a WB card
(X-Rite, Opteka, etc.).
The gray 18% thing is about setting the exposure, not the white balance.
Of course you can use the gray card for white balance too but it's not its
main purpose. Typically gray 18 targets are white on the other side for WB.
Often white balance cards came in set of three pieces: white, gray and
black. Almost always the gray here is not gray 18 so it is not good for
exposure reference only for WB.
Bye
Lorenzo
Post by I. Ivanov
For the purpose of white balance - I don't think it really matters if it
is 18% or less or more. It is just pure gray. As long as you use a card and
then use it to measure white balance you should be fine.
Well, I guess I can try to print a gray card!
Anyone know what the code is for 18% gray? If 18% is right in the middle
of the shades of gray I found one page (http://www.computerhope.com/c
808080
and according to the same page it is made up of equal part RGB
*W3C Color Name:* Grey
*RGB:* 128, 128, 128
*HSL:* 0.00, 0.00, 0.50
so what is the authoritative answer?
Post by Michael
is there something where we can take a picture of a gray card and then
we click on it and then dt will adjust all of the colors so that the gray
card is
33-33-33%?
Usually you use "18% gray" meaning a card that reflects 18% of the light
in the visible spectrum and equal amounts of red, green and blue.
It might actually be nice if the whitebalance module would support
exposure adjustment as well, to make a selected area a specific brightness,
or what do others think?
by the way: what is the color of the remaining 1%
That "33-33-33%" is your invention, so nobody but you can know what
"remaining 1%" you are talking about. If you were talking about the
reflected % of the individual color channels then there is no "remaining
1%", but the "remaining" (absorbed) amounts of light are 67%, 67% and 67%,
respectively.
- Marcus
--
____________________________________________________________________________
darktable user mailing list to unsubscribe send a mail to
____________________________________________________________________________
darktable user mailing list to unsubscribe send a mail to
____________________________________________________________________________
darktable user mailing list to unsubscribe send a mail to
Lorenzo Bolzani
2017-02-22 18:17:42 UTC
Permalink
Hi Jean-Luc,
how would you proceed in detail with this module? Would you start with the
lift, gain or gamma or a little from all three? How many patches would you
pick?

I have a few pictures with heavy color casts (from slide scanning) and
while I can get good results the effort is often very high and I have yet
to find a reliable way to simplify the process.

Here is an example:

https://www.flickr.com/photos/***@N04/32240744713/in/dateposted-public/

https://www.flickr.com/photos/***@N04/32929837971/in/dateposted-public/


I just tried to use the color balance module on this shot, as I did several
other times, but I never got great results. The same for Lab curves. The
best result I've got, the one above, was using "color mapping" but I
consider it pure luck.

In this picture there is nothing clearly neutral so it is quite hard to use
about anything.


Thanks for any suggestion



Bye

Lorenzo

2017-02-22 10:39 GMT+01:00 Jean-Luc Coulon (f5ibh) <
Post by Jean-Luc Coulon (f5ibh)
Hi,
I think this post is going outside the original question.
The original question was about a grey card and white balance (I I
understood corrrectly).
And what to do if the grey card doesnt appear "neutral" in darktable.
1 - Grey card and white balance.
The fact that the card is 18%, 22% or anything else is unrelevant if we
speak of white balance (the 18% is useful for exposure control... well, I
will no enter the debate about calibration and the various mid-grey,
median-grey or so)
So, yes, we can set the white balance using the "spot" white balance on a
grey card as soon as the grey is neutral.
Neutral means "the same value for red, green, blue".
2 - Card is not neutral
If the grey is not neutral, say a colour cast with one of the channel with
a different value, your white balance will give a colour cast in the
opposite direction.
You can correct that in dt with the module "colour balance" for instance
by selecting the neutral area of interest with the colour picker and trying
to have the same value for all the 3 channels.
But, in my opinion, if your grey card is reasonably neutral, you well not
see (with your eyes) any difference.
A simple sheet of (white) paper can also do the job.
About the reflectivity of the neutral grey : it is an other matter. Such
grey card can be used to adjust the exposure. But as there are strong
controversies about what should be the neutrality of a neutral grey, this
subject is prone to leave to various trolls.
Regards
Jean-Luc
Post by Lorenzo Bolzani
Printing a gray card is a bad idea: you need a very good an perfectly
calibrated printer for this and good non-glossy paper. Otherwise you do not
get perfect gray and you get a random shade of color in all your shots
where you use it. Just buy one.
For white balance, as Ivanov said, any gray is good, actually you
typically use a white card. So *just take a white sheet from the printer
a use that.* I did this in several occasions and works really fine. The
minor problem is that paper is not "perfectly neutral white" but can vary
slightly so if you are looking for ultimate perfection buy a WB card
(X-Rite, Opteka, etc.).
The gray 18% thing is about setting the exposure, not the white balance.
Of course you can use the gray card for white balance too but it's not its
main purpose. Typically gray 18 targets are white on the other side for WB.
Often white balance cards came in set of three pieces: white, gray and
black. Almost always the gray here is not gray 18 so it is not good for
exposure reference only for WB.
Bye
Lorenzo
Post by I. Ivanov
For the purpose of white balance - I don't think it really matters if it
is 18% or less or more. It is just pure gray. As long as you use a card and
then use it to measure white balance you should be fine.
Well, I guess I can try to print a gray card!
Anyone know what the code is for 18% gray? If 18% is right in the middle
of the shades of gray I found one page (http://www.computerhope.com/c
808080
and according to the same page it is made up of equal part RGB
*W3C Color Name:* Grey
*RGB:* 128, 128, 128
*HSL:* 0.00, 0.00, 0.50
so what is the authoritative answer?
Post by Michael
is there something where we can take a picture of a gray card and then
we click on it and then dt will adjust all of the colors so that the gray
card is
33-33-33%?
Usually you use "18% gray" meaning a card that reflects 18% of the
light in the visible spectrum and equal amounts of red, green and blue.
It might actually be nice if the whitebalance module would support
exposure adjustment as well, to make a selected area a specific brightness,
or what do others think?
by the way: what is the color of the remaining 1%
That "33-33-33%" is your invention, so nobody but you can know what
"remaining 1%" you are talking about. If you were talking about the
reflected % of the individual color channels then there is no "remaining
1%", but the "remaining" (absorbed) amounts of light are 67%, 67% and 67%,
respectively.
- Marcus
--
____________________________________________________________________________
darktable user mailing list to unsubscribe send a mail to
____________________________________________________________________________
darktable user mailing list to unsubscribe send a mail to
____________________________________________________________________________
darktable user mailing list to unsubscribe send a mail to
____________________________________________________________________________
darktable user mailing list to unsubscribe send a mail to
Michael
2017-02-22 20:23:13 UTC
Permalink
I always thought white balance should be done off of a white card not that
I understand how (why might be a better term) selecting an area of a color
(or even multiple colors) adjusts all colors or how it does it. I would
think if you should select a 18% gray/ x brightness white card area the
computer should adjust that area to be that gray/white and adjust the RGB
colors around it to match. That is what I meant originally.

In any case..... how do you use the gray card to set exposure.
(also.... please cc the list because the only reason I got this message
from Lorenzo is because it was in someones inline)
Post by Michael
Post by Michael
Post by Lorenzo Bolzani
Printing a gray card is a bad idea: you need a very good an perfectly
calibrated printer for this and good non-glossy paper. Otherwise you do not
get perfect gray and you get a random shade of color in all your shots
where you use it. Just buy one.
For white balance, as Ivanov said, any gray is good, actually you
typically use a white card. So *just take a white sheet from the
printer a use that.* I did this in several occasions and works really
fine. The minor problem is that paper is not "perfectly neutral white" but
can vary slightly so if you are looking for ultimate perfection buy a WB
card (X-Rite, Opteka, etc.).
The gray 18% thing is about setting the exposure, not the white balance.
Of course you can use the gray card for white balance too but it's not its
main purpose. Typically gray 18 targets are white on the other side for WB.
Often white balance cards came in set of three pieces: white, gray and
black. Almost always the gray here is not gray 18 so it is not good for
exposure reference only for WB.
Bye
Lorenzo
Post by I. Ivanov
For the purpose of white balance - I don't think it really matters if
it is 18% or less or more. It is just pure gray. As long as you use a card
and then use it to measure white balance you should be fine.
Well, I guess I can try to print a gray card!
Anyone know what the code is for 18% gray? If 18% is right in the
middle of the shades of gray I found one page (
http://www.computerhope.com/cgi-bin/htmlcolor.pl?c=808080) that says
808080
and according to the same page it is made up of equal part RGB
*W3C Color Name:* Grey
*RGB:* 128, 128, 128
*HSL:* 0.00, 0.00, 0.50
so what is the authoritative answer?
Post by Michael
is there something where we can take a picture of a gray card and then
we click on it and then dt will adjust all of the colors so that the gray
card is
33-33-33%?
Usually you use "18% gray" meaning a card that reflects 18% of the
light in the visible spectrum and equal amounts of red, green and blue.
It might actually be nice if the whitebalance module would support
exposure adjustment as well, to make a selected area a specific brightness,
or what do others think?
by the way: what is the color of the remaining 1%
That "33-33-33%" is your invention, so nobody but you can know what
"remaining 1%" you are talking about. If you were talking about the
reflected % of the individual color channels then there is no "remaining
1%", but the "remaining" (absorbed) amounts of light are 67%, 67% and 67%,
respectively.
- Marcus
--
____________________________________________________________________________
darktable user mailing list to unsubscribe send a mail to
____________________________________________________________________________
darktable user mailing list to unsubscribe send a mail to
____________________________________________________________________________
darktable user mailing list to unsubscribe send a mail to
____________________________________________________________________________
darktable user mailing list to unsubscribe send a mail to
____________________________________________________________________________
darktable user mailing list to unsubscribe send a mail to
--
:-)~MIKE~(-:
Michael
2017-02-22 20:25:51 UTC
Permalink
The reason I didn't get it is that it was sent to spam.... sorry about the
clutter
Post by Michael
I always thought white balance should be done off of a white card not that
I understand how (why might be a better term) selecting an area of a color
(or even multiple colors) adjusts all colors or how it does it. I would
think if you should select a 18% gray/ x brightness white card area the
computer should adjust that area to be that gray/white and adjust the RGB
colors around it to match. That is what I meant originally.
In any case..... how do you use the gray card to set exposure.
(also.... please cc the list because the only reason I got this message
from Lorenzo is because it was in someones inline)
Post by Michael
Post by Michael
Post by Lorenzo Bolzani
Printing a gray card is a bad idea: you need a very good an perfectly
calibrated printer for this and good non-glossy paper. Otherwise you do not
get perfect gray and you get a random shade of color in all your shots
where you use it. Just buy one.
For white balance, as Ivanov said, any gray is good, actually you
typically use a white card. So *just take a white sheet from the
printer a use that.* I did this in several occasions and works really
fine. The minor problem is that paper is not "perfectly neutral white" but
can vary slightly so if you are looking for ultimate perfection buy a WB
card (X-Rite, Opteka, etc.).
The gray 18% thing is about setting the exposure, not the white
balance. Of course you can use the gray card for white balance too but it's
not its main purpose. Typically gray 18 targets are white on the other side
for WB.
Often white balance cards came in set of three pieces: white, gray and
black. Almost always the gray here is not gray 18 so it is not good for
exposure reference only for WB.
Bye
Lorenzo
Post by I. Ivanov
For the purpose of white balance - I don't think it really matters if
it is 18% or less or more. It is just pure gray. As long as you use a card
and then use it to measure white balance you should be fine.
Well, I guess I can try to print a gray card!
Anyone know what the code is for 18% gray? If 18% is right in the
middle of the shades of gray I found one page (
http://www.computerhope.com/cgi-bin/htmlcolor.pl?c=808080) that says
808080
and according to the same page it is made up of equal part RGB
*W3C Color Name:* Grey
*RGB:* 128, 128, 128
*HSL:* 0.00, 0.00, 0.50
so what is the authoritative answer?
Post by Michael
is there something where we can take a picture of a gray card and
then we click on it and then dt will adjust all of the colors so that the
gray card is
33-33-33%?
Usually you use "18% gray" meaning a card that reflects 18% of the
light in the visible spectrum and equal amounts of red, green and blue.
It might actually be nice if the whitebalance module would support
exposure adjustment as well, to make a selected area a specific brightness,
or what do others think?
by the way: what is the color of the remaining 1%
That "33-33-33%" is your invention, so nobody but you can know what
"remaining 1%" you are talking about. If you were talking about the
reflected % of the individual color channels then there is no "remaining
1%", but the "remaining" (absorbed) amounts of light are 67%, 67% and 67%,
respectively.
- Marcus
--
____________________________________________________________________________
darktable user mailing list to unsubscribe send a mail to
____________________________________________________________________________
darktable user mailing list to unsubscribe send a mail to
____________________________________________________________________________
darktable user mailing list to unsubscribe send a mail to
____________________________________________________________________________
darktable user mailing list to unsubscribe send a mail to
____________________________________________________________________________
darktable user mailing list to unsubscribe send a mail to
--
--
:-)~MIKE~(-:
Serge Schmitt
2017-02-22 18:58:13 UTC
Permalink
Hello !
Post by Jean-Luc Coulon (f5ibh)
A simple sheet of (white) paper can also do the job.
I dont think so, because you cannot be sure that the white is neutral.
Actually: yes and no...

If the work is critical or professionnal, précise reproduction of paintings
for exemple, I strongly suggest buying a grey card or better a Macbeth
chart. It's worth the cost in gaining rapidity and precision of the
processing.

If the work is "artistic", you can adjust to taste with your own open eyes.
Because art is actually nothing else as a matter of taste...

So, for the majority of the photographers out there (and for me... example)
who use Darktable, the WB settings of their camera are just fine and need
(eventually) a very little amount of tweaking in DT.

My two cents !

Serge

P.S. Just to say: I photography for about 55 years now, and as time goes, I
rely more and more confidently on the "auto" and even "full auto" functions
of my recent cameras. Their exposure scale exceed so largely the possibilty
of both screens and papers. Only here and there I want to expose more
accurately for certain images, backlit for exemple. One cannot save an
overexposed image, digital photography is a "positiv" process as where
transparencies.

So my rules:
1. never overexpose.
2. if you want a consistancy of exposure for a serie (which highly
facilitates the post-processing) mesure accurately once and set manual.
And that's it for the rules... ;-)

Why struggle if no necessity?
Martin Burri
2017-02-22 20:27:13 UTC
Permalink
There is a way more reliable DIY way than printing:
https://photographylife.com/diy-reliable-and-cheap-universal-white-balance-reference-device

I tried it and compared the result with a real gray card. I was unable
to see a difference between both methods. So, teflon comes close enough
at least for my visual perception :-)

Best regards,
Martin
Post by Michael
Well, I guess I can try to print a gray card!
Anyone know what the code is for 18% gray? If 18% is right in the
middle of the shades of gray I found one page
(http://www.computerhope.com/cgi-bin/htmlcolor.pl?c=808080) that says
808080
and according to the same page it is made up of equal part RGB
*W3C Color Name:* Grey
*RGB:* 128, 128, 128
*HSL:* 0.00, 0.00, 0.50
so what is the authoritative answer?
is there something where we can take a picture of a gray card
and then we click on it and then dt will adjust all of the
colors so that the gray card is
33-33-33%?
Usually you use "18% gray" meaning a card that reflects 18% of the
light in the visible spectrum and equal amounts of red, green and
blue.
It might actually be nice if the whitebalance module would support
exposure adjustment as well, to make a selected area a specific
brightness, or what do others think?
by the way: what is the color of the remaining 1%
That "33-33-33%" is your invention, so nobody but you can know
what "remaining 1%" you are talking about. If you were talking
about the reflected % of the individual color channels then there
is no "remaining 1%", but the "remaining" (absorbed) amounts of
light are 67%, 67% and 67%, respectively.
- Marcus
--
____________________________________________________________________________
darktable user mailing list to unsubscribe send a mail to
Michael
2017-02-22 22:26:50 UTC
Permalink
So with raw and dt it is okay to zoom in on the spot? What I mean is when
you take the picture do you take one (with the white spot in it) or two
(one with and one without). I'm thinking two but just to be sure.....

You know..... I actually like this idea. I'm going to tape a couple of
pieces of white printer paper together and then tape that to a folder and
use that to white balance off of.
so with raw and dt it is okay to zoom in on the spot? What I mean is when
you take the picture do you take one (with the white spot in it) or twon
(one with and one without). I'm thinking two but just to be sure.....
If you shoot in raw then it only needs to give a big enough patch to use
the dt white balance tool on it.
If tuning the in-camera white-balance setting, then i think you must
refer to the camera manual, since there is probably no universal answer.
Best regards,
Martin
sounds good.... but shouldn't it be bigger? Or else.... how close can you
be when taking the white balance picture? An exposure picture off of a gray
card? So it does NOT need to cover most of the field of view?
https://photographylife.com/diy-reliable-and-cheap-universal
-white-balance-reference-device
I tried it and compared the result with a real gray card. I was unable to
see a difference between both methods. So, teflon comes close enough at
least for my visual perception :-)
Best regards,
Martin
Well, I guess I can try to print a gray card!
Anyone know what the code is for 18% gray? If 18% is right in the middle
of the shades of gray I found one page (http://www.computerhope.com/c
808080
and according to the same page it is made up of equal part RGB
*W3C Color Name:* Grey
*RGB:* 128, 128, 128
*HSL:* 0.00, 0.00, 0.50
so what is the authoritative answer?
is there something where we can take a picture of a gray card and then we
click on it and then dt will adjust all of the colors so that the gray card
is
33-33-33%?
Usually you use "18% gray" meaning a card that reflects 18% of the light
in the visible spectrum and equal amounts of red, green and blue.
It might actually be nice if the whitebalance module would support
exposure adjustment as well, to make a selected area a specific brightness,
or what do others think?
by the way: what is the color of the remaining 1%
That "33-33-33%" is your invention, so nobody but you can know what
"remaining 1%" you are talking about. If you were talking about the
reflected % of the individual color channels then there is no "remaining
1%", but the "remaining" (absorbed) amounts of light are 67%, 67% and 67%,
respectively.
- Marcus
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Michael
2017-02-22 22:34:00 UTC
Permalink
I found a DIY gray card for those interested in this kind of thing.
https://shuttertux.wordpress.com/2012/01/18/do-it-yourself-18-grey-card/
Post by Michael
So with raw and dt it is okay to zoom in on the spot? What I mean is when
you take the picture do you take one (with the white spot in it) or two
(one with and one without). I'm thinking two but just to be sure.....
You know..... I actually like this idea. I'm going to tape a couple of
pieces of white printer paper together and then tape that to a folder and
use that to white balance off of.
so with raw and dt it is okay to zoom in on the spot? What I mean is
when you take the picture do you take one (with the white spot in it) or
twon (one with and one without). I'm thinking two but just to be sure.....
If you shoot in raw then it only needs to give a big enough patch to use
the dt white balance tool on it.
If tuning the in-camera white-balance setting, then i think you must
refer to the camera manual, since there is probably no universal answer.
Best regards,
Martin
sounds good.... but shouldn't it be bigger? Or else.... how close can
you be when taking the white balance picture? An exposure picture off of a
gray card? So it does NOT need to cover most of the field of view?
https://photographylife.com/diy-reliable-and-cheap-universal
-white-balance-reference-device
I tried it and compared the result with a real gray card. I was unable
to see a difference between both methods. So, teflon comes close enough at
least for my visual perception :-)
Best regards,
Martin
Well, I guess I can try to print a gray card!
Anyone know what the code is for 18% gray? If 18% is right in the middle
of the shades of gray I found one page (http://www.computerhope.com/c
808080
and according to the same page it is made up of equal part RGB
*W3C Color Name:* Grey
*RGB:* 128, 128, 128
*HSL:* 0.00, 0.00, 0.50
so what is the authoritative answer?
is there something where we can take a picture of a gray card and then
we click on it and then dt will adjust all of the colors so that the gray
card is
33-33-33%?
Usually you use "18% gray" meaning a card that reflects 18% of the light
in the visible spectrum and equal amounts of red, green and blue.
It might actually be nice if the whitebalance module would support
exposure adjustment as well, to make a selected area a specific brightness,
or what do others think?
by the way: what is the color of the remaining 1%
That "33-33-33%" is your invention, so nobody but you can know what
"remaining 1%" you are talking about. If you were talking about the
reflected % of the individual color channels then there is no "remaining
1%", but the "remaining" (absorbed) amounts of light are 67%, 67% and 67%,
respectively.
- Marcus
--
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darktable user mailing list to unsubscribe send a mail to
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darktable user mailing list to unsubscribe send a mail to
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Michael
2017-02-23 02:36:08 UTC
Permalink
or if you want enter the HTML code for it. It is 808080..... or is it
80808080! I'm pretty sure that the first will work.
Post by Michael
I found a DIY gray card for those interested in this kind of thing.
https://shuttertux.wordpress.com/2012/01/18/do-it-yourself-18-grey-card/
Post by Michael
So with raw and dt it is okay to zoom in on the spot? What I mean is
when you take the picture do you take one (with the white spot in it) or
two (one with and one without). I'm thinking two but just to be sure.....
You know..... I actually like this idea. I'm going to tape a couple of
pieces of white printer paper together and then tape that to a folder and
use that to white balance off of.
so with raw and dt it is okay to zoom in on the spot? What I mean is
when you take the picture do you take one (with the white spot in it) or
twon (one with and one without). I'm thinking two but just to be sure.....
If you shoot in raw then it only needs to give a big enough patch to
use the dt white balance tool on it.
If tuning the in-camera white-balance setting, then i think you must
refer to the camera manual, since there is probably no universal answer.
Best regards,
Martin
sounds good.... but shouldn't it be bigger? Or else.... how close can
you be when taking the white balance picture? An exposure picture off of a
gray card? So it does NOT need to cover most of the field of view?
https://photographylife.com/diy-reliable-and-cheap-universal
-white-balance-reference-device
I tried it and compared the result with a real gray card. I was unable
to see a difference between both methods. So, teflon comes close enough at
least for my visual perception :-)
Best regards,
Martin
Well, I guess I can try to print a gray card!
Anyone know what the code is for 18% gray? If 18% is right in the
middle of the shades of gray I found one page (
http://www.computerhope.com/cgi-bin/htmlcolor.pl?c=808080) that says
808080
and according to the same page it is made up of equal part RGB
*W3C Color Name:* Grey
*RGB:* 128, 128, 128
*HSL:* 0.00, 0.00, 0.50
so what is the authoritative answer?
is there something where we can take a picture of a gray card and then
we click on it and then dt will adjust all of the colors so that the gray
card is
33-33-33%?
Usually you use "18% gray" meaning a card that reflects 18% of the
light in the visible spectrum and equal amounts of red, green and blue.
It might actually be nice if the whitebalance module would support
exposure adjustment as well, to make a selected area a specific brightness,
or what do others think?
by the way: what is the color of the remaining 1%
That "33-33-33%" is your invention, so nobody but you can know what
"remaining 1%" you are talking about. If you were talking about the
reflected % of the individual color channels then there is no "remaining
1%", but the "remaining" (absorbed) amounts of light are 67%, 67% and 67%,
respectively.
- Marcus
--
____________________________________________________________________________
darktable user mailing list to unsubscribe send a mail to
____________________________________________________________________________
darktable user mailing list to unsubscribe send a mail to
--
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--
--
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Serge Schmitt
2017-02-23 06:49:37 UTC
Permalink
Post by Michael
or if you want enter the HTML code for it. It is 808080..... or is it
80808080! I'm pretty sure that the first will work.
#808080

The method described (with Gimp) is also simple.

For my experience a gray print is too approximative and cannot be used for
accurate mesuring, but ok for learning the process.

Otherways,

For exposition, not for white balance, most ones have a sort of greycard
with them : the palm of a caucasian skinned reflects just one stop over the
middle gray. Place this palm in the same light and overexpose one stop.


Serge
Serge Schmitt
2017-02-23 08:53:56 UTC
Permalink
(One can apply the same attitude for the digital process despite the fact
that it's a positiv process.)

Le jeudi 23 février 2017 07:49:37 Serge Schmitt wrote but slipped on the
(non accuracy of a grey print) Otherways,
aquiring mindst a greychart would be mandatory in order to print this
calibrated... greychart! Whoops! ;-)

One can find cheapo (about $10) but sufficiently accurate and weather
resistant gray/white/black charts, just search under "grey chart" on Amazon
or eBay or such. They can perfectly be used to correct the color balance of
your printer for all day use, or to calibrate a serie of images in DT.

Use them at the beginning of a shooting and as long as the "lightery" is
constant, as for an indoor match for example. Outdoors, the in camera
settings are sufficienly precise. For certain reportages, especially music
performances, it's mostly impossible to set a "logical" WB. Fortunately
emotion prevals widely here on accuracy, noise and such things.

As I said in an other post, a totally calibrated environment would be
mandatory for photometric accurate work. It involves thousands of $$$... But
you know it, photometry is not photography! If you doubt, look at the videos
made by Harry Durgin:
https://www.youtube.com/channel/UCngiFhMSngeFwUGtsXA-17w. I watched a couple
of them. His usage of DT is wonderfully powerful and his resulting images
are splendid!

Philosophies I learnt (costly):
- although I'm toxicly passioned with post-processing, releasing makes
better and more images than geekery and hours of computing.
- the best camera is those you have with you, would it be a cheapo compact
or even a low end phone.

Also said by Ansel Adams: it's better to process the images after a few
monthes in order to have a fresh sight of them. Not on air in those times of
speedyness...

My two cents,
Serge
Martin Burri
2017-02-23 12:40:56 UTC
Permalink
Serge, like you write: Also in my eyes, more important than a gray card
is a calibrated Monitor which is good enough to display the colors
accurately (in my case a Dell UP2717D but there are many other options).

And, what I also find important, neutral-white environment light. I
bought a simple light bulb (Philips TL-D 90 DeLuxe - maybe TL-D Graphica
might be even better). It was much cheaper than the monitor and it
really helps. Prints (coming from a calibrated printing service) look
now very close to what I see on the monitor. (I calibrated the monitor
white point to 5300K which is equal to the light bulb).

I own a gray card but I almost never use it. I usually set the white
balance where it looks good to me. Sometimes even a bit towards the one
or the other side depending on the mood I want to have in the picture. I
don't care too much about "exact" physical white balance.

Of course, I can only tell about me - others might think differently.

Best regards,
Martin
Post by Serge Schmitt
(One can apply the same attitude for the digital process despite the fact
that it's a positiv process.)
Le jeudi 23 février 2017 07:49:37 Serge Schmitt wrote but slipped on the
(non accuracy of a grey print) Otherways,
aquiring mindst a greychart would be mandatory in order to print this
calibrated... greychart! Whoops! ;-)
One can find cheapo (about $10) but sufficiently accurate and weather
resistant gray/white/black charts, just search under "grey chart" on Amazon
or eBay or such. They can perfectly be used to correct the color balance of
your printer for all day use, or to calibrate a serie of images in DT.
Use them at the beginning of a shooting and as long as the "lightery" is
constant, as for an indoor match for example. Outdoors, the in camera
settings are sufficienly precise. For certain reportages, especially music
performances, it's mostly impossible to set a "logical" WB. Fortunately
emotion prevals widely here on accuracy, noise and such things.
As I said in an other post, a totally calibrated environment would be
mandatory for photometric accurate work. It involves thousands of $$$... But
you know it, photometry is not photography! If you doubt, look at the videos
https://www.youtube.com/channel/UCngiFhMSngeFwUGtsXA-17w. I watched a couple
of them. His usage of DT is wonderfully powerful and his resulting images
are splendid!
- although I'm toxicly passioned with post-processing, releasing makes
better and more images than geekery and hours of computing.
- the best camera is those you have with you, would it be a cheapo compact
or even a low end phone.
Also said by Ansel Adams: it's better to process the images after a few
monthes in order to have a fresh sight of them. Not on air in those times of
speedyness...
My two cents,
Serge
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Serge Schmitt
2017-02-23 20:46:39 UTC
Permalink
Hello Martin and the list.

I post a bit long because, altough I know this list is dedicated to
Darkable, of which I'm an "afficionado", it seems important to me to share
here and then some thoughts about technique, mandatory related with post-
processing, after more than fifty years snapping around.

Another good rule as foreword: After listening to a photo preacher (me?)
take a look at his images... If they touch you anyhow - I really don't speak
about "good" or "bad" but about emotions! - it could actually be worth to
continue listening or reading. If not, it would be in most cases better to
pass your way.

Link to some the images I speak about is at the end of the post... ;-)
Post by Martin Burri
Serge, like you write: Also in my eyes, more important than a gray card
is a calibrated Monitor which is good enough to display the colors
accurately (in my case a Dell UP2717D but there are many other options).
And, what I also find important, neutral-white environment light. I
bought a simple light bulb (Philips TL-D 90 DeLuxe - maybe TL-D Graphica
might be even better). It was much cheaper than the monitor and it
really helps. Prints (coming from a calibrated printing service) look
now very close to what I see on the monitor. (I calibrated the monitor
white point to 5300K which is equal to the light bulb).
I own a gray card but I almost never use it. I usually set the white
balance where it looks good to me. Sometimes even a bit towards the one
or the other side depending on the mood I want to have in the picture. I
don't care too much about "exact" physical white balance.
Of course, I can only tell about me - others might think differently.
Best regards,
Martin
What in my mind was important to say à propos struggling with WB:

a) Overall, as your post proves it, the colorimetric results depends on the
whole environnement and chain and in fact on a myriad of variables.

For example, and most people overlook this, with wich body you snap? The
color rendition are different from one manufacturer to another nonobstand
identical sensors. I would certainly take more care of that at the moment of
acquiring a system, than of his WB setting capabilities. As of digital
cameras, I owned a Canon G3 (2003), then a Panasonic G1 (2009, the very
first µ4/3 with an electronic 100% viewfinder) and to day an Olympus E-M5
(2013). The rendering I love the best comes out of the Canon, to day I cope
happily with the Oly E-M5 outputs but I found, together with other people,
that the rendering of the Panasonic is a bit pissy in the yellows area. As
are said the Sony's. And also, each lenses has a different color cast.
And... so on. Another (stupid?) example: If I read well some testings (and
looked well some galleries), buying a Fuji "trans" body and producing raws
should be a real stupidity...

b) printing a DIY grey card is not a goog idea without the help of mindst a
calibrated... grey card. We used them in the past to help the use of
handheld then inbuilt cells, I even used a spotmeter for a time, essentially
because "the making of a photograph" (title of a serie of books by Ansel
Adams) was a long and costly process. And making transparencies was a no
repentance process. Even Early BW films were not so tolerant to exposition
failures. To say it's only useful for professional critical work.

A fast look on Flickr, Ipernity or even Instagram proves that there are a
lot of talented photographer out there who know just nothing about theory.
That considerably refreshes the photographic art. That is also helped with
the fact that the "marginal cost" of producing numeric images equals nut, so
you can make gazillions of images for about nothing, once acquired a basic
gear. Experimenting is no longer costly.

At the times of negatives or transparencies that was another history. I have
recently calculated that the "programmed obsolescence" is to day less costly
for me than where films days with the same second hand bodies 20 years long.
Buying a new gear about each four years for about 2 grands costs me less
than costed me films and developpement on a same period, nothing said about
convenience! And not even to speak of blocking the access to the family
bathroom hours and hours. To day, a guy I know well "develops" his images
sitting his armchair... :-) Going for a trip needed me about three films a
day, you can imagine the size of the bag for a fortnight outing... To day,
one only has marginal costs if one prints, what I seldom do.

c) When listening to a Symphony played by Berstein or Karajan, who cares on
wich frequency the A was tuned that day? Who cares on the WB settings when
looking at photographs on the Net or even in a gallery? The mood, as you
said, and the style and the emotions created are more important.

And yes Dartable is a fabulously multitalented "grand orchestre" with which
I just love to interpret my originals.

The only "critical" technical variable in digital photography is exposing:
never never never overexpose! All other reasonnable technical tweeks can be
done afterwood.

Composition is the real and first target of making an "artistic" image. A
photographer can learn about it in books about painting too: the rules (?)
are the same. Yes, the photographic art is all about composition and
eventually color. So accurate colorimetry or photometry, nor gear, really
matter. Who, in a gallery, cares of what sort of pinsel a painter used?
Another painter, eventually? But not the gallery owner nor the audience.

And yes I'm really more and more confident on the manufacturers automatic
settings.

And yes I shoot my family and social images mostly in jpeg. No audience ever
cared.

On my last acquisition, a high end compact, I will tune a preset on 50mm
equivalent and "Super Intelligent Auto" (yes, yes!). And let go. :-) So
while strolling I will be feeling like a "mini Henri Cartier Bresson" who
used only one lense, one film and two settings, one for outdoors and one for
indoors. In the thirties, a Leica body with his basic lens costed more than
an arm and a leg. That's the real reason why he was from the beginning a
"one lens shooter": he couldn't afford more. Later he understanded that
using only one lens (50mm) and one film (TRI-X) made him a better street
shooter. The outputs of a today high end compact camera are of better
technical quality that the film with which he made a few of his most
celebrated images. So for Ansel Adams, in a lesser way. That tells us that
technical globbledigloop does't matter so highly. Cartie Bresson was gritty
on not cropping his images. Composition, composition... that's the first
what we see on an image. Ansel Adams, in his domain, was also highly aware
of composition. Composition is that's what real matters, so all the
dedicated modules in DT and others are unevaluable! Under others, of
course... :-)

Last sunday I made my first "test shooting stroll" with this compact. I'm
amazed! Some results are here:
http://www.ipernity.com/doc/sergeschmitt/44348154//in/album/963120 .
Originals are (more than 300) jpegs, 'cause I have to switch to a more up to
date Kubuntu before beeing able to use the last DT with those raws. I don't
really care, as you probably guess after reading me! :-) I have "built" a
style for them, and found that the consistency is correct. On "good old
times" I would have had to carry around about ten pounds of gear to obtain
the same and probably not better varied images. But these ones are done with
a less then three film cases sized little gear. A blessing for my 70 years
old surgeried backbone and injuried knee... ;-)

I am fully booked until Tuesday, so I wish you (all) a good WE.

Please forgive my froggish english, and thanks to those couraged enough to
read all my prose.

Best regards,
Serge
Chris Siebenmann
2017-02-23 15:41:52 UTC
Permalink
Post by Martin Burri
I own a gray card but I almost never use it. I usually set the white
balance where it looks good to me. Sometimes even a bit towards the
one or the other side depending on the mood I want to have in the
picture. I don't care too much about "exact" physical white balance.
I completely agree that the final white balance in the picture is an
artistic choice. Some pictures are well served by having whites be
white; others are much better with explicit color casts in various
directions depending on the photo.

What I like grey cards and other source of technically correct white
balances for is as a starting point. I'm not confident of my own ability
to accurately judge tints, especially subtle ones, so getting the white
balance technically correct is something I find useful to take all
of that out of the picture. If I've neutralized all tints, I can be
confident that anything I put back in is there deliberately and through
choice, and isn't just an accident that I didn't notice (but that other
people may).

('That other people may notice' is really the thing I worry about. I'm
not willing to trust that I won't accidentally overlook a semi-subtle
tint in the photograph that other people will notice right away because
they're coming to the picture without preconceptions and without having
seen it before. I have certainly done similar things before, where a
picture looked perfectly good to me when I initially processed it but
then I came back a month later and realized that oh gosh the whole thing
had a weird tint that I'd completely overlooked.)

- cks
Tim Rolph
2017-02-23 18:23:07 UTC
Permalink
Post by Michael
is there something where we can take a picture of a gray card and then we
click on it and then dt will adjust all of the colors so that the gray card
is
33-33-33%?
by the way: what is the color of the remaining 1%
Anyone wanting a grey / white balance / 24 patch color card should checkout
the following.

www.greywhitebalancecolourcard.co.uk

I have one of these and am very pleased with it and it's a fraction of the
cost of the Mcbeth cards.
Steven Fosdick
2017-02-23 22:25:53 UTC
Permalink
Note that if you take a picture of a white card and fill the frame with it
in an auto-exposure mode it will come out grey anyway.

What I am not sure has been completely addresses is how all of this would
work together. I assume you would not have a card in each shot but would
start a shoot with the card and the proceed to take photos of the subject
you really want. When you get the pictures into DT you'd want to set the
white balance from the card in the first pic and then apply it to the rest
of the pictures.

Let's assume you opened the first picture, select spot white balance,
select a decent region in the middle of the card, then returned to light
table mode and copy the white balance setting from that first picture to
the rest. What I am not sure about is whether it would copy the white
balance numbers, i.e. the adjustment to R, G and B or whether it would copy
the intent, i.e. copy parameters to the white balance module that say
select rectangle x,y,w,h and use that to do spot white balance. If the
latter it would not give the desired effect.
Post by Tim Rolph
Post by Michael
is there something where we can take a picture of a gray card and then we
click on it and then dt will adjust all of the colors so that the gray
card
Post by Michael
is
33-33-33%?
by the way: what is the color of the remaining 1%
Anyone wanting a grey / white balance / 24 patch color card should checkout
the following.
www.greywhitebalancecolourcard.co.uk
I have one of these and am very pleased with it and it's a fraction of the
cost of the Mcbeth cards.
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________________
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KOVÁCS István
2017-02-24 07:28:31 UTC
Permalink
It copies the numbers
Post by Steven Fosdick
Note that if you take a picture of a white card and fill the frame with it
in an auto-exposure mode it will come out grey anyway.
What I am not sure has been completely addresses is how all of this would
work together. I assume you would not have a card in each shot but would
start a shoot with the card and the proceed to take photos of the subject
you really want. When you get the pictures into DT you'd want to set the
white balance from the card in the first pic and then apply it to the rest
of the pictures.
Let's assume you opened the first picture, select spot white balance,
select a decent region in the middle of the card, then returned to light
table mode and copy the white balance setting from that first picture to
the rest. What I am not sure about is whether it would copy the white
balance numbers, i.e. the adjustment to R, G and B or whether it would copy
the intent, i.e. copy parameters to the white balance module that say
select rectangle x,y,w,h and use that to do spot white balance. If the
latter it would not give the desired effect.
Post by Tim Rolph
Post by Michael
is there something where we can take a picture of a gray card and then
we
Post by Michael
click on it and then dt will adjust all of the colors so that the gray
card
Post by Michael
is
33-33-33%?
by the way: what is the color of the remaining 1%
Anyone wanting a grey / white balance / 24 patch color card should checkout
the following.
www.greywhitebalancecolourcard.co.uk
I have one of these and am very pleased with it and it's a fraction of the
cost of the Mcbeth cards.
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Marcus Sundman
2017-02-24 23:38:01 UTC
Permalink
Post by Tim Rolph
Post by Michael
is there something where we can take a picture of a gray card and then we
click on it and then dt will adjust all of the colors so that the gray card
is
33-33-33%?
by the way: what is the color of the remaining 1%
Anyone wanting a grey / white balance / 24 patch color card should checkout
the following.
www.greywhitebalancecolourcard.co.uk
I have one of these and am very pleased with it and it's a fraction of the
cost of the Mcbeth cards.
Well, first we need sensible support for color cards in darktable. (Now
you have to go through crazy many hoops to set your whitebalance from a
color card, including multiple import/export and profile generation in
an external program and custom command line tools and whatnot.)

- Marcus
Michael
2017-02-25 01:08:27 UTC
Permalink
You know..... actually just going to the original photo (history 0) and
then applying a sony alpha base curve to it made it almost perfect. I then
rotated it and applied color correction and it was perfect after a little
adjustment of the exposure.
Post by Marcus Sundman
Well, first we need sensible support for color cards in darktable. (Now
you have to go through crazy many hoops to set your whitebalance from a
color card, including multiple import/export and profile generation in an
external program and custom command line tools and whatnot.)
What do you mean?
--
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:-)~MIKE~(-:
--
:-)~MIKE~(-:
Remco Viëtor
2017-02-25 15:10:36 UTC
Permalink
Post by Marcus Sundman
Well, first we need sensible support for color cards in darktable. (Now
you have to go through crazy many hoops to set your whitebalance from a
color card, including multiple import/export and profile generation in
an external program and custom command line tools and whatnot.)
First you need a correctly calibrated and profiled screen (and printer if you
plan on printing). Without that, you'd have to work strictly by the numbers,
because there's no way you can visualise the final result. (OK, if you publish
on the web, >90% of the viewers won't have a profiled screen, but at least you
know how it should look)

Then, setting your white balance from a *colour* card is looking for trouble
(if it is at all possible to get any decent white balance from such a card).

As has been said already, for a white balance, you need a neutral spot in your
image: light or dark gray, but not white or black. (Such a spot can of course
be a *neutral* spot on your colour card). Remember that 'setting the white
balance' means changing the ratios green/red and green/blue (in practice,
green is set to 1.0, and the red and blue channels are multiplied by one value
each, depending on colour temperature and tint, DT _shows_ those multipliers
in the white balance module, and allows you to change them directly).

When you have that neutral spot in your image, in DT it's just a matter of
choosing the "spot" mode in the white balance module and select a rectangle on
the neutral spot.

The colour patches are used to create a *camera profile*, and yes, this needs
an external programme (or two), just like screen or printer profiling.
*Unlike* screen and printer profiling, it's something that's mostly needed for
very colour critical work. (the few times I bothered with a camera profile,
the results with a custom profile were identical or nearly identical to the
default profile and I had no way to show which was better) And when you get to
that level, you also have to be very careful about your lights all having the
same colour, as the colour of the incoming lights influences what the camera
"sees".

And just a small question: is there *any* raw developer that includes the
possibility to generate an input profile from a colour card?

Remco
Tim Rolph
2017-02-25 18:29:58 UTC
Permalink
Hello, the card I use is two sided, it has white grey and black on one side
and the standard 24 colors on the other and yes you can use Adobe DNG to
produce a color profile for use in Lightroom and rawtherapee. However I use it
mostly for a custom WB in camera on my 14 year old DSLR canon it is just a
matter of taking one full frame image of the WB side of the card and then
telling the camera to use the custom WB image. Of course you need to change
images if the lighting changes significantly and you can also use it within dt
with the spot wb option.
While on the subject of colour profiles I have recently used the excellent
darktable-chart programme to create a profile and tone curve using a wolf faust
it8 scanner calibration target that I purchased for 15.00 euros back in 2009
and I can say it is better that any other profile that I have produced using
any other method.

Tim.
Post by Remco Viëtor
Post by Marcus Sundman
Well, first we need sensible support for color cards in darktable. (Now
you have to go through crazy many hoops to set your whitebalance from a
color card, including multiple import/export and profile generation in
an external program and custom command line tools and whatnot.)
First you need a correctly calibrated and profiled screen (and printer if
you plan on printing). Without that, you'd have to work strictly by the
numbers, because there's no way you can visualise the final result. (OK, if
you publish on the web, >90% of the viewers won't have a profiled screen,
but at least you know how it should look)
Then, setting your white balance from a *colour* card is looking for trouble
(if it is at all possible to get any decent white balance from such a card).
As has been said already, for a white balance, you need a neutral spot in
your image: light or dark gray, but not white or black. (Such a spot can of
course be a *neutral* spot on your colour card). Remember that 'setting the
white balance' means changing the ratios green/red and green/blue (in
practice, green is set to 1.0, and the red and blue channels are multiplied
by one value each, depending on colour temperature and tint, DT _shows_
those multipliers in the white balance module, and allows you to change
them directly).
When you have that neutral spot in your image, in DT it's just a matter of
choosing the "spot" mode in the white balance module and select a rectangle
on the neutral spot.
The colour patches are used to create a *camera profile*, and yes, this
needs an external programme (or two), just like screen or printer
profiling. *Unlike* screen and printer profiling, it's something that's
mostly needed for very colour critical work. (the few times I bothered with
a camera profile, the results with a custom profile were identical or
nearly identical to the default profile and I had no way to show which was
better) And when you get to that level, you also have to be very careful
about your lights all having the same colour, as the colour of the incoming
lights influences what the camera "sees".
And just a small question: is there *any* raw developer that includes the
possibility to generate an input profile from a colour card?
Remco
____________________________________________________________________________
darktable user mailing list
Tim Rolph
2017-02-25 19:18:59 UTC
Permalink
Before anyone points out the error, darktable-chart produces a style that
contains a color-lut and tone curve that either corrects that image to look
like the refernce image, whether that be in camera jpeg or another processors
output ie CaptureOne or just the reference data for your color chart. and not
an icc profile.

Tim.
Post by Tim Rolph
Hello, the card I use is two sided, it has white grey and black on one side
and the standard 24 colors on the other and yes you can use Adobe DNG to
produce a color profile for use in Lightroom and rawtherapee. However I use
it mostly for a custom WB in camera on my 14 year old DSLR canon it is just
a matter of taking one full frame image of the WB side of the card and then
telling the camera to use the custom WB image. Of course you need to change
images if the lighting changes significantly and you can also use it within
dt with the spot wb option.
While on the subject of colour profiles I have recently used the excellent
darktable-chart programme to create a profile and tone curve using a wolf
faust it8 scanner calibration target that I purchased for 15.00 euros back
in 2009 and I can say it is better that any other profile that I have
produced using any other method.
Tim.
Post by Remco Viëtor
Post by Marcus Sundman
Well, first we need sensible support for color cards in darktable. (Now
you have to go through crazy many hoops to set your whitebalance from a
color card, including multiple import/export and profile generation in
an external program and custom command line tools and whatnot.)
First you need a correctly calibrated and profiled screen (and printer if
you plan on printing). Without that, you'd have to work strictly by the
numbers, because there's no way you can visualise the final result. (OK, if
you publish on the web, >90% of the viewers won't have a profiled screen,
but at least you know how it should look)
Then, setting your white balance from a *colour* card is looking for
trouble (if it is at all possible to get any decent white balance from
such a card).
As has been said already, for a white balance, you need a neutral spot in
your image: light or dark gray, but not white or black. (Such a spot can of
course be a *neutral* spot on your colour card). Remember that 'setting the
white balance' means changing the ratios green/red and green/blue (in
practice, green is set to 1.0, and the red and blue channels are multiplied
by one value each, depending on colour temperature and tint, DT _shows_
those multipliers in the white balance module, and allows you to change
them directly).
When you have that neutral spot in your image, in DT it's just a matter of
choosing the "spot" mode in the white balance module and select a rectangle
on the neutral spot.
The colour patches are used to create a *camera profile*, and yes, this
needs an external programme (or two), just like screen or printer
profiling. *Unlike* screen and printer profiling, it's something that's
mostly needed for very colour critical work. (the few times I bothered with
a camera profile, the results with a custom profile were identical or
nearly identical to the default profile and I had no way to show which was
better) And when you get to that level, you also have to be very careful
about your lights all having the same colour, as the colour of the incoming
lights influences what the camera "sees".
And just a small question: is there *any* raw developer that includes the
possibility to generate an input profile from a colour card?
Remco
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__ darktable user mailing list
to unsubscribe send a mail to
____________________________________________________________________________
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David Vincent-Jones
2017-02-25 20:38:15 UTC
Permalink
Try changing the 'input color profile' ... the 'linear XYZ' appears to
make for a reasonable starting profile, some of the other profiles may
also be of interest ... the infrared is different!!

David
Post by Tim Rolph
Before anyone points out the error, darktable-chart produces a style that
contains a color-lut and tone curve that either corrects that image to look
like the refernce image, whether that be in camera jpeg or another processors
output ie CaptureOne or just the reference data for your color chart. and not
an icc profile.
Tim.
Post by Tim Rolph
Hello, the card I use is two sided, it has white grey and black on one side
and the standard 24 colors on the other and yes you can use Adobe DNG to
produce a color profile for use in Lightroom and rawtherapee. However I use
it mostly for a custom WB in camera on my 14 year old DSLR canon it is just
a matter of taking one full frame image of the WB side of the card and then
telling the camera to use the custom WB image. Of course you need to change
images if the lighting changes significantly and you can also use it within
dt with the spot wb option.
While on the subject of colour profiles I have recently used the excellent
darktable-chart programme to create a profile and tone curve using a wolf
faust it8 scanner calibration target that I purchased for 15.00 euros back
in 2009 and I can say it is better that any other profile that I have
produced using any other method.
Tim.
Post by Remco Viëtor
Post by Marcus Sundman
Well, first we need sensible support for color cards in darktable. (Now
you have to go through crazy many hoops to set your whitebalance from a
color card, including multiple import/export and profile generation in
an external program and custom command line tools and whatnot.)
First you need a correctly calibrated and profiled screen (and printer if
you plan on printing). Without that, you'd have to work strictly by the
numbers, because there's no way you can visualise the final result. (OK, if
you publish on the web, >90% of the viewers won't have a profiled screen,
but at least you know how it should look)
Then, setting your white balance from a *colour* card is looking for
trouble (if it is at all possible to get any decent white balance from
such a card).
As has been said already, for a white balance, you need a neutral spot in
your image: light or dark gray, but not white or black. (Such a spot can of
course be a *neutral* spot on your colour card). Remember that 'setting the
white balance' means changing the ratios green/red and green/blue (in
practice, green is set to 1.0, and the red and blue channels are multiplied
by one value each, depending on colour temperature and tint, DT _shows_
those multipliers in the white balance module, and allows you to change
them directly).
When you have that neutral spot in your image, in DT it's just a matter of
choosing the "spot" mode in the white balance module and select a rectangle
on the neutral spot.
The colour patches are used to create a *camera profile*, and yes, this
needs an external programme (or two), just like screen or printer
profiling. *Unlike* screen and printer profiling, it's something that's
mostly needed for very colour critical work. (the few times I bothered with
a camera profile, the results with a custom profile were identical or
nearly identical to the default profile and I had no way to show which was
better) And when you get to that level, you also have to be very careful
about your lights all having the same colour, as the colour of the incoming
lights influences what the camera "sees".
And just a small question: is there *any* raw developer that includes the
possibility to generate an input profile from a colour card?
Remco
__________________________________________________________________________
__ darktable user mailing list
to unsubscribe send a mail to
____________________________________________________________________________
darktable user mailing list
____________________________________________________________________________
darktable user mailing list
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