Re: R: [APML]: Scanner Bit Depth

["Philip Perkins" <philip@astrocruise.com>]

The Astro-Photography Mailing List
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Hi Marco

> Philip, I wouldn't say something wrong but I think that you can work in the
> 12/16 bit channel depth just by acting in the twain interface.
> I have a flat scanner that give 10 bit per channel (30 bit) but I can get
> this resolution in Photoshop. I discovered that I can operate in the twain
> interface modifying the curve selector and so getting a "pre" stretching of
> the histogram. I strongly believe that the twain interface works at the
> scanner hardware resolution (30 bit or more)

I have also wondered whether a TWAIN import might overcome this bit
restriction and get me the full 36 bits.  In fact I have tried importing via
TWAIN into PS a number of times but I am puzzled by the way it works. When I
import, it brings up the Sprintscan window and does the import successfully.
However I cannot get at the image in PS until I close down the Sprintscan
window. This seems to be crazy because as soon as I close the Sprintscan
window I loose all my settings. The TWAIN interface seems to assume that you
can always get the image exactly right by prescan adjustments only and that
you will never need to adjust the settings and do a rescan. In fact this is
never the case - I always adjust the image according to the PS Levels, and I
always have to do rescans to get this just right. Sometimes I do as many as
6 rescans before the image is perfect. Working in this way, I have found
the TWAIN import to be impossible to use. Maybe I am missing something.

What I always do is to have PS and Sprintscan opened simultaneously as two 
separate applications in Windows 95. I do the scan in the Sprintscan window 
and then Alt-Tab to the PS window and open the image I just scanned - i.e.  
I save it to disk in the meantime.  This may be cumbersome but it's the only 
way I have found of doing repeated tweaks to the Exposure in the Sprintscan 
software and inspecting the result in PS.  If the TWAIN interface worked the 
way I wanted I agree it would be quicker and nicer to use. It should be 
possible to Minimize the scanner window so that you can get at the image and 
inspect the Levels, while keeping the scanner application alive, so that 
Exposure adjustments can be made.  But it doesn't even allow the scanner 
window to be Minimized - nothing can be done with the image until the 
scanner application is completely closed. Sounds strange to me... if anyone 
knows an answer it would interesting.

Thanks
--Philip

Philip Perkins  --  philip@astrocruise.com
51 27'N 1 36'W  --  Wiltshire, UK
43 54'N 5 32'E  --  Luberon, France
Astrocruise     --  http://www.astrocruise.com