[sane-devel] Affordable film scanner

[Laurent-jan]

Jonathan Buzzard wrote:

> ukd@xenon.pc.Uni-Koeln.DE said:
<...>
> 
>>First of all, truncation is an option, not a must. Second, you usually
>>want to end up with JPEGs, and that implies 3x8 bit encoding. 
>>
> 
> Speak for yourself then. Even if your final output is a JPEG you
> almost certainly want a greater bit-depth for the digital darkroom.
> I certainly have needed greater than 8bit images for many scanned
> negatives.
> 
> JAB.
> 



12 bits does not always provide more information than 8 bits.
When you do large gamma-corrections, you may find that the
sample-resolution in the darker areas are actually just 8 bit or
even less.  I can even see the noise from lowest bits in the shadows
(Nikon LS-2000). Ofcourse, you get some additional bits in
the lighter areas, but that hardly improves the overall image.

Many people use the GIMP. That implies an 8-bit color. For a
GIMP-plugin the solution of truncating to 8 bits would be welcome.
The idea is, that the 8 bits/color that are transfered to GIMP
contain the maximum of information.


Anyway, you'll want to truncate as late as possible, or do as much

with your colors as possible before truncating. That means

that gamma-correction in the backend is better than using the
GIMP. The same goes for the removal of the orange-mask on negatives,
or the color-correction of film types or age for slides. If you
use other software than the GIMP, you may even choose to truncate
just before saving as JPEG. So truncating should be optional.

ljm


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