[Darktable-users] X-Trans images with moiré (in DT but not in LR)

[Francisco Cribari]

I have been noticing moiré in several Fujifilm RAW files (.RAF, X-Trans).
Here is an example:

RAW file: https://dl.dropboxusercontent.com/u/2171814/_FFX7922.RAF

XMP (RAW): https://dl.dropboxusercontent.com/u/2171814/_FFX7922_01.RAF.xmp

JPG (SOOC): Loading Image...

XMP (JPG): https://dl.dropboxusercontent.com/u/2171814/_FFX7922.JPG.xmp

There is moiré in the blue shirt in the RAW file, but not in the SOOC JPG.
(Take a look, e.g., at the area between his camera and his vest after
zooming in.) Even with Markesteijn 3-pass demosaic + five times color
smoothing I still see moiré.

I wanted to find out whether this is a Fujifilm-related issue or a
Darktable-related issue, so I asked a friend to open the RAW file in
Lightoom (version 5.7.64) and export a full resolution JPG. (Since all my
computers rum Linux, I do not access to LR.) Here is the resulting JPG:

JPG exported by Lightroom:
Loading Image...

I see no moiré.

Is there a way to get rid of moiré in X-Trans images when using Darktable?
Comments and tips and welcome. Best, Francisco

[Marc Cousin]

I have been noticing moiré in several Fujifilm RAW files (.RAF,
RAW file: https://dl.dropboxusercontent.com/u/2171814/_FFX7922.RAF
XMP (RAW): https://dl.dropboxusercontent.com/u/2171814/_FFX7922_01.RAF.xmp
JPG (SOOC): https://dl.dropboxusercontent.com/u/2171814/_FFX7922.JPG
XMP (JPG): https://dl.dropboxusercontent.com/u/2171814/_FFX7922.JPG.xmp
There is moiré in the blue shirt in the RAW file, but not in the SOOC
JPG. (Take a look, e.g., at the area between his camera and his vest
after zooming in.) Even with Markesteijn 3-pass demosaic + five times
color smoothing I still see moiré.
I wanted to find out whether this is a Fujifilm-related issue or a
Darktable-related issue, so I asked a friend to open the RAW file in
Lightoom (version 5.7.64) and export a full resolution JPG. (Since all
https://dl.dropboxusercontent.com/u/2171814/_FFX7922b.jpg
I see no moiré.
Is there a way to get rid of moiré in X-Trans images when using
Darktable? Comments and tips and welcome. Best, Francisco

Hi, I've been toying with your import.

What was weird was that I didn't get the moiré at all with my default
settings. After a bit of trial and error, I found that it's my profiled
denoise (wavelet, on color) that removes the moiré. It seems logical
afterwards, but maybe you'll get a better explanation by one of the
experts on the mailing list. Meanwhile, give a try to this setting.

I could improve a bit the result by being more agressive with the
denoising (as the camera must have done, as the resolution on the shirt
isn't that wonderful on the SOOC jpeg), then removing fringing.

Here are the jpeg I managed to get

http://dl.free.fr/rm.pl?h=qplZFfYAV&i=71793947&s=RYsfRXzrsDAPVfCLYHWtaTqwzUvwNVao

and the XMP

http://dl.free.fr/rm.pl?h=v5E43Q0ZK&i=71793977&s=NhKwhz2Am1DoTsJTr3YgOrmXNQCNiHA8


Regards

Marc

[Marc Cousin]

Post by Marc Cousin
Hi, I've been toying with your import.
What was weird was that I didn't get the moiré at all with my default
settings. After a bit of trial and error, I found that it's my profiled
denoise (wavelet, on color) that removes the moiré. It seems logical
afterwards, but maybe you'll get a better explanation by one of the
experts on the mailing list. Meanwhile, give a try to this setting.
I could improve a bit the result by being more agressive with the
denoising (as the camera must have done, as the resolution on the shirt
isn't that wonderful on the SOOC jpeg), then removing fringing.
Here are the jpeg I managed to get
http://dl.free.fr/rm.pl?h=qplZFfYAV&i=71793947&s=RYsfRXzrsDAPVfCLYHWtaTqwzUvwNVao
and the XMP
http://dl.free.fr/rm.pl?h=v5E43Q0ZK&i=71793977&s=NhKwhz2Am1DoTsJTr3YgOrmXNQCNiHA8
Regards
Marc

Ok, new try as the files seems to have been removed. I don't know how I
messed up :)

https://drive.google.com/folderview?id=0B_liIOwDeWUmQnBLOXdaS3FBT3c&usp=sharing

[S. Witt]

Post by Marc Cousin
I found that it's my profiled
denoise (wavelet, on color) that removes the moiré.

Yes, that is exactly the way I handle it as well. You could also try the
bilateral denoise tool, which however is a little harder to handle. In
any way, it is important to set the blend mode to color or HSV color. A
while ago I used the color blend mode (not my own image, so I cannot
show it) causing colors to smear noticeable into areas of different
colors. This was gone with HSV color mode. This method also helps to
handle color moire in fine details which tend to occur in X-Trans.
Note that this color denoising may also have slight negative effects and
I would recommend to apply it selectively on such an image.

BTW: What I have seen so far from Lightroom is that it applies color
denoising by default. You can sometimes see, that colors appear to be
washed out a little in X-Trans files similar to what is caused by using
the denoising methods mentioned above in darktable.


Cheers
Sören