Thumbnails not color-managed + severely distorted shadow tonality for thumbs, previews

Andrey Goreev aegoreev at
Wed Nov 15 20:16:17 GMT 2017

Try to play with settings in the following tabs:

Settings - Configure digiKam - Image - RAW Behavior
Settings - Configure digiKam - Views - Preview

On Wednesday, November 15, 2017 1:08:59 PM MST, Elle Stone wrote:
> On 11/15/2017 02:08 PM, Maik Qualmann wrote:
>> The thumbnails are color managed. But the color depth of the thumbnails is
>> only 8 bit, that's probably the cause.
> Hmm, no, on my monitor, if color management isn't being used, 
> the image has a slight magenta color cast. All the digiKam 
> thumbnails have a slight magenta color cast that for example 
> changes the color of blue skies to make them slightly more 
> purple, and also gives grayscale images a slight magenta color 
> cast. This is completely separate from and independent of the 
> crushed/posterized shadows in the thumbnails. The previews don't 
> have the magenta color cast, but the thumbnails do.
> But yes, the fact that the thumbnails are 8-bits accounts for 
> the crushed/posterized shadows for the thumbnails, but hopefully 
> not also for the previews. Are the previews 8-bits also? Because 
> the tonality in the previews doesn't have the type of posterized 
> shadows I'd expect from a linear gamma 8-bit image. Rather the 
> shadows are crushed with fairly abrupt transitions but not 
> completely posterized tonal shifts.
> Now that you've explained why the shadows are posterized for 
> the thumbnails, I should have realized that was the issue - I 
> suspect thumbnails are only 8-bits fairly universally. But 
> magenta color cast for the thumbnails is another issue 
> altogether.
> If you are saying the thumbnails *should* be color-managed (and 
> the settings would indicate that yes, they should be), how do I 
> troubleshoot why they are showing the typical (for my monitor, 
> no doubt not for all monitors) magenta color cast that results 
> when I view images in non-color-managed applications?


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