Section 4 of this article (Working Space vs Output Space) talks about the importance of using the least restricting colour space in your post-processing software … which leads me to the following questions;
Which colour space do the Nik Collection tools use as their working space ?
When exporting to, say, Color Efex Pro (eg. from PhotoLab), which ICC profile am I best to use ?
I don’t think the question in the original post has been answered. Since that time, PL has introduced a larger working color space, “DxO Wide Gamut”, and the Nik Collection has been completely upgraded. However, I haven’t heard anything about what color space the apps in the Nik Collection do their work in. That would be nice to know.
The answer appears to be Adobe RGB (by inference):
So I did a quick experiment with PL7.0.1_76 (Windows) set to Wide Gamut working color space, opened different files and exported them to Nik 5 Color Efex 5 and saved them without any change.
raw-file with camera set to sRGB → ICC profile AdobeRGB
raw-file with camera set to ARGB → ICC profile AdobeRGB
tif-file in ProPhoto colour space → ICC profile AdobeRGB
tif-file in sRGB colour space → ICC profile AdobeRGB
Comparing the files from # 3. I could see the loss of colour after export.
When comparing the files from # 4., there was no visible difference (export from small to wider colour space doesn’t add something magically).