Strange processing behaviour - Nikon NEF-file

Software RawTherapee
1

I encounter some strange processing behaviour with RawTherapee Ver. 4.2 and it would seem, it affects esp. overexposed areas. They get purple. (see cutout).
The full Nikon .NEF-file is available here: http://filebin.net/x2qwe8jo2b
Do I probably have to change the standard settings to get rid of this?

For a Canon D700 the same problem is mentioned here: Canon 700D: overburned pixels are purple colored · Issue #3248 · Beep6581/RawTherapee · GitHub
and the answer refers to missing data in the file camconst.json. I have checked this file on my PC (ubuntu 14.04) and found Nikon D700 data is there.

2

Hello Claudio,

I am not a RawTherapee expert but ,On Windows 7 (64 bit), with version 4.2.915, (GTK 3 branch) everything looks fine.

I have simply opened your NEF with all standard options (Amaze demosaic method) and there is no artifact (purple areas).

See image:

1366×768 846 KB

EDIT
I have just tried myself to recover the over-exposed areas of your image by simply applying some " Expositions" methods (ALT+E shortcut).
However, I am unable to reproduce the purple areas later on since, I suppose, we are using different options for doing so…

3

I have tried your image image with RT Branch: gtk3 Version: 4.2.927 on Linux Ubuntu. For this screen pic I have only increased the “Highlight Compression” and selected “Colour Propagation” from the default opening settings. I have no colour artefacts.

However, I did get your colour effect with Retinex turned on set to any Strength above 3. Even with Mask Method set to Highlight.

4

Thanks for your input David. I also changed the setting (Highlight Compression) and I could replicate your result.

5

The Nikon D700 is handled correctly by RawTherapee using neutral settings.

1916×1057 1.08 MB

To recover/reconstruct highlights as much as possible, see:
http://rawpedia.rawtherapee.com/Exposure#Highlight_Reconstruction

6

Sometimes i get purple in overexposed areas when I use Retinex, in this case I change the white point (in the Raw tab) to some higher value…

7

Exactly, and use the “Highlights” Retinex method. But magenta highlights caused by Retinex are not a bug and occur in all clipped raw images, not just Nikon D700 ones.