[Digikam-users] Bad embedded preview

[botta at pik-potsdam.de]

Here a screenshot (digikam 1.2.0) to exemplify the problem: 

The thumbnail views of the DNG and of the JPG files are quite similar
but the embedded JPG preview (of the DNG file, on the left of the light
table) is remarkably different from the reduced size preview (of the JPG
file, on the right).

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My understanding is that previews of DNG files (via the in-DNG embedded
JPG file or via RAW decoding always apply brightness auto-correction no
matter what the settings are.

If this is the case, I would argue it is an error. As I pointed out in
my original post, this behavior makes previews of DNG files virtually
unusable and forces users to save both DNG and JPG files to card.

If I am missing something, please let me know. Any help is highly
appreciated. 

Best, 
Nicola



Nicola Botta <nicola at pik-potsdam.de> wrote:

> With 
> 
> Qt: 4.6.3
> KDE Development Platform: 4.4.5 (KDE 4.4.5)
> digiKam: 1.2.0
> 
> and, more recently
> 
> Qt: 4.7.4
> KDE Development Platform: 4.7.4 (4.7.4)
> digiKam: 1.9.0
> 
> I have consistently experienced the same problem when working with DNGs
> and JPGs generated by Ricoh GXR modules:
> 
> For a given picture, the thumbnail views of both the DNG and of the JPG
> files are fine. Import (RAW decoding) of the DNG file is fine too with
> Auto-Brightness unchecked. The JPG preview is also fine but the DNG
> preview often looks horrible.
> 
> No matter whether "Embedded preview loads full-sized images" is checked
> or unchecked, DNG previews often look quite different from their JPG
> counterparts *AND* from from their raw decoding imports. 
> 
> In many cases, DNG previews look like raw decodings with Auto-Brightness
> checked. It is as if brightness always was auto-adjusted in DNG
> previewing.
> 
> This is quite frustrating since it makes DNGs unusable for previewing
> and forces me to save both DNGs and JPGs versions of the same picture.
> 
> Any idea how to solve this problem ? Any help is highly
> appreciated. Best, Nicola
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