[Digikam-users] Histogram does not match embedded preview for raw files in browse mode

Alson van der Meulen alm at flutnet.org
Wed Apr 29 15:31:35 BST 2015

Hello all,

I have a NEF file of picture of a gray wall. The histogram (in camera and in any raw converter I tried including Digikam's own edit mode) shows a narrow peak below value 192 in all channels. In browse mode (thumbnail, preview, light table) Digikam shows the embedded 8-bit JPEG preview. The histogram shown in the sidebar, however, shows 16-bit RGB values and indicates a severe overexposure. I'm guessing this is based on a raw conversion which does some sort of auto-levels adjustment that goes wrong. Either that or a botched 8-bit to 16-bit conversion.

I don't use Digikam as a raw converter, but setting the raw decoding to 8-bit and disabling auto brightness does not make any difference. Since Digikam shows the embedded preview in browse mode, I would also expect the histogram to match the preview. This would be especially useful when using UniWB to make the preview histogram match the raw histogram. Is there any setting that I might have missed to change this behavior? Am I missing something or is this a bug?

This is with Digikam 4.9.0 from Philip Johnsson's PPA on Ubuntu 14.10. Here is a screen shot of the histogram of the NEF file on the left and the histogram of the embedded JPEG extracted with dcraw -e on the right:

Thanks in advance,

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