RawTherapee - Strange color cast with Nikon Z6 NEF file

Software RawTherapee
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#1

Hi to all,

I’m really new to RawTherapee.
I’m developing some of my files in order to practicing with RT and understand all the module.

I have developed a Nikon Z6 file and I’m looking a strange green cast in some sky areas near green leafs instead of the sky color.

Z6 RT color cast
Z6 RT color cast1089×550 1.09 MB

I use the AMAZE demosaicing algorithm; I’m trying others with the same result.
The input color profile used is Camera Standard; the working profile and output profile is ProPhoto.

I’ve opened the same file in Camera Raw and also in Darktable (in this case with the same demosaicing algorithm) but there is no green cast in the sky.

What can be the problem?

Thanks in advance,

Francesco

#2

Have you enabled Raw chromatic abberration correction? This seems like an artifact of that.

#3

Hi, thank you for your reply.
Yes, it is enabled in automatic mode.

Forgot to report that the RT version is the latest stable.

Best Regards,

Francesco

#4

grafik

#5

Thank you.

Done, nothing changed.

Best Regards,

Francesco

#6

Can you provide the NEF? Then we can try to find the culprit.

#7

Sure, attached.

Thank you.

Francesco
_DSC4092.NEF (32.2 MB)

#8

Thanks for the NEF. I can not reproduce the color cast in current dev version of RT. Looks like it’s already fixed. Can you also provide the .pp3 file please?

#9

Hello,

thank you for the feedback.
Attached you find the .pp3.

Best Regard,

Francesco
_DSC4092.NEF.pp3 (12.2 KB)

#10

Thanks for the .pp3. Looks like an issue with noise reduction. At least disabling noise reduction gets rid of the color cast.

1 Like
#11

Yes, noise reduction is way to aggressive (mode + chrominance master). The avoid colour shift also plays a roll, albeit small.

One other thing: Why did you choose for this specific output profile? You might consider setting it to RTv4_sRGB as default.

1 Like
#12

It’s interesting that this image fared so poorly with noise reduction. I know that I can’t really use it without significant tweaking when shooting brick buildings. Even details where individual bricks are a large part of the image get colour shifted into a muddy* tone.

Is it that certain colours or certain scales of detail are affected?

*perhaps one might expect bricks to be muddy… but I assure you they get way muddier.

#13

Not really, in my opinion.

This is a ISO 100 shot. The default noise reduction (chroma master at standard 15 + standard curve, and no luminance reduction dailled in) does a very nice job.

You can get a step better by setting demoaicing to RCD+VNG4 (at its default calculated values) in this case.

Those are basically the default settings. Some fine-tuning could get it even a bit better, I’m sure.

Using Local Contrast + Microcontrast + Contrast by Details Level, as is the case here, does increase the noise slightly, though.

I have a Z6 II and am rather pleased at how it and RT handle noise together (at all levels up to and including ISO 12800). Do have to honest here and say that 6400+ need some extra stuff (mainly wavelets + Impulse noise reduction), but I’m not getting waxy/plastic end results.

#14

Perhaps I’m misunderstanding but. My surprise was not about poor noise reduction, because iso100, but rather that it started eating colours at that scale and that aggressively.

I’m as I mentioned already quite vary of nr but now I realise I have to look out in a broader set of photos. I’m a time limited post processor and always produce many never one image. This means it’s easy for me to miss unexpected behaviour in modules.

#15

RawTherapee does what you tell it to do. If you say that it needs to denoise aggressively and use 25 as setting for the chrominance master, as is the case here, it will do so, even though that isn’t at all what one should do with a ISO 100 image.

Ah, OK.

You do might want to consider spending an afternoon creating some good baseline, auto applied noise reduction setting for your specific camera(s). It will make sure that your end-result will look a lot less plasticy/waxy.

You don’t mention what camera you have, but just in case: Denoise profiles for a Nikon Z6 II

#16

Hello and thank you very much for the explanations.

It’s my fault. I try to create a “base” profile for the camera ignoring that the Chroma Noise Reduction may affect the colours (I made this because on Camera Raw the colors are not affected by the Color NR even if the NR is set to 100).
Usually I don’t use the Luminance NR even at high ISO but only the Chrominance NR and, at this point, I’m a little bit confused on how to correctly set it on RT but I will read the documentation.

About the output profile, usually I use ProPhoto to export from Camera Raw to Photoshop because for what I know it is the profile with the widest gamut.

Thank you very much again and Best Regards,

Francesco

#17

Disable noise reduction for your base profile. Then tweak noise reduction at various iso’s and ctrl+save a partical profile containing only the noise reduction (you can add other iso specific settings if you want such as less/disabled sharpening etc.) by checking the tickboxes. The you can create enable dynamic profiles for you camera/iso combination.
https://rawpedia.rawtherapee.com/Dynamic_processing_profiles

I think you were unlucky with your scene. In many cases you won’t see strange colour behaviour when using noise reduction. Some scenes trigger it and as I mention above I was interested to see that you scene was affected.