strange thumbnails

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strange thumbnails

Alexander Linkenbach
Hi

when I scan my black and white pics and save them in 8 or 16bit dng format I
get distorted thumbnails in digikam, like three mini versions in a row in the
upper third of the thumbnail and "random" black and white data in the lower
two thirds. This does not happen if I save them as 24, 48 or 64 bit. Now I
could save all my b/w pics in 24bit, but
that means 110MB instead of 32 per MF picture.
If I look at the scans with a different viewer (gwenview) the behavior is
opposite, ie only the 8 and 16bit saves give me proper thumbnails. In dolphin
it depends on the thumbnail size: I get correct thumbnails for all scans at
80pix but the same as with gwenview for bigger thumbnails.
And: the file info in digikam for all scans actually shows 16bit, no matter how
I saved them.
Am I doing something wrong here?

Alex

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Re: strange thumbnails

Gilles Caulier-4
Hi,

How do you generate your DNG file from your scan workflow ? Not with
digiKam, i'm sure...

Gilles Caulier

2017-05-27 19:04 GMT+02:00 Alexander Linkenbach <[hidden email]>:

> Hi
>
> when I scan my black and white pics and save them in 8 or 16bit dng format I
> get distorted thumbnails in digikam, like three mini versions in a row in the
> upper third of the thumbnail and "random" black and white data in the lower
> two thirds. This does not happen if I save them as 24, 48 or 64 bit. Now I
> could save all my b/w pics in 24bit, but
> that means 110MB instead of 32 per MF picture.
> If I look at the scans with a different viewer (gwenview) the behavior is
> opposite, ie only the 8 and 16bit saves give me proper thumbnails. In dolphin
> it depends on the thumbnail size: I get correct thumbnails for all scans at
> 80pix but the same as with gwenview for bigger thumbnails.
> And: the file info in digikam for all scans actually shows 16bit, no matter how
> I saved them.
> Am I doing something wrong here?
>
> Alex
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Re: strange thumbnails

Alexander Linkenbach
Salut, Giles
Files are scanned from negatives by vuescan directly into raw dng, but the thumbnails in dk are produced by dk, I assume. Different viewers give me different thumbnails, although not all produce useful results.
Ciao
Alex

Enviado desde mi iPhone

> El 16 jun 2017, a las 9:44, Gilles Caulier <[hidden email]> escribi├│:
>
> Hi,
>
> How do you generate your DNG file from your scan workflow ? Not with
> digiKam, i'm sure...
>
> Gilles Caulier
>
> 2017-05-27 19:04 GMT+02:00 Alexander Linkenbach <[hidden email]>:
>> Hi
>>
>> when I scan my black and white pics and save them in 8 or 16bit dng format I
>> get distorted thumbnails in digikam, like three mini versions in a row in the
>> upper third of the thumbnail and "random" black and white data in the lower
>> two thirds. This does not happen if I save them as 24, 48 or 64 bit. Now I
>> could save all my b/w pics in 24bit, but
>> that means 110MB instead of 32 per MF picture.
>> If I look at the scans with a different viewer (gwenview) the behavior is
>> opposite, ie only the 8 and 16bit saves give me proper thumbnails. In dolphin
>> it depends on the thumbnail size: I get correct thumbnails for all scans at
>> 80pix but the same as with gwenview for bigger thumbnails.
>> And: the file info in digikam for all scans actually shows 16bit, no matter how
>> I saved them.
>> Am I doing something wrong here?
>>
>> Alex

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Re: strange thumbnails

Gilles Caulier-4
Yes DK thumbnails are generated by DK while scanning DNG. If DNG
format used by VueScan is "special" (as it do not support the standard
TIFF/EP), this kind of result will be visible. In background Exiv2 is
used to extract DNG thumbnails.

I recommend to not use DNG for this kind of scan, but TIFF as well,
with LZW compression.

Gilles Caulier

2017-06-16 12:22 GMT+02:00 Alex Linkenbach <[hidden email]>:

> Salut, Giles
> Files are scanned from negatives by vuescan directly into raw dng, but the thumbnails in dk are produced by dk, I assume. Different viewers give me different thumbnails, although not all produce useful results.
> Ciao
> Alex
>
> Enviado desde mi iPhone
>
>> El 16 jun 2017, a las 9:44, Gilles Caulier <[hidden email]> escribi├│:
>>
>> Hi,
>>
>> How do you generate your DNG file from your scan workflow ? Not with
>> digiKam, i'm sure...
>>
>> Gilles Caulier
>>
>> 2017-05-27 19:04 GMT+02:00 Alexander Linkenbach <[hidden email]>:
>>> Hi
>>>
>>> when I scan my black and white pics and save them in 8 or 16bit dng format I
>>> get distorted thumbnails in digikam, like three mini versions in a row in the
>>> upper third of the thumbnail and "random" black and white data in the lower
>>> two thirds. This does not happen if I save them as 24, 48 or 64 bit. Now I
>>> could save all my b/w pics in 24bit, but
>>> that means 110MB instead of 32 per MF picture.
>>> If I look at the scans with a different viewer (gwenview) the behavior is
>>> opposite, ie only the 8 and 16bit saves give me proper thumbnails. In dolphin
>>> it depends on the thumbnail size: I get correct thumbnails for all scans at
>>> 80pix but the same as with gwenview for bigger thumbnails.
>>> And: the file info in digikam for all scans actually shows 16bit, no matter how
>>> I saved them.
>>> Am I doing something wrong here?
>>>
>>> Alex
>
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