Pedro Côrte-Real schrieb am 29.12.2014 um 21:54:
> On Mon, Dec 29, 2014 at 8:42 PM, Bernhard <[email protected]> 
> wrote:
>> No, as it is from a scanner it indeed is RGB. The fourth channel is IR for
>> dust cleaning and saved as alpha channel within the TIF.
> Well the scanner has some kind of sensor inside it, so it's at least
> in theory possible to have actual bayer raw from it.
not for "conventional" scanners, as a linear line of photocells is moved 
mechanically along the film.
Alternatively you can use this setup:
http://www.dpbestflow.org/camera/camera-scanning
to get a "true raw" as we know it :-)
>   I think Leaf
> sells some scanners that produce actual raw files for example. The IR
> channel indeed explains the fourth channel.
>
>> So I will stick with TIFF.
> Actually if there's an option to produce just a 3 channel DNG (without
> the IR alpha channel)
that's not an option for me since I want to digitize my archive only 
once and keep ALL information the scanner deliveres for potential future 
use and improvement of the results.
And negatives seem to be very sensitive to scratches :-( .
>   it will probably work but will be the exact same
> data as TIFF so it's probably not worth it.
Tim Gray explains the different options of "RAW scanning" in Vuescan here
http://www.rangefinderforum.com/forums/showpost.php?p=1843660&postcount=2
and he also comes to the conclusion we worked out here:
> Lastly, and I think the best, RAW TIFF: gamma 1, no funny file formats.
so thanks again. You helped me "stabilize my workflow".

-- 
regards
Bernhard

http://www.bilddateien.de


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