Marko Cebokli wrote:
> These ae some of my observations (and wishes) concernig the
> transparency adapter for the UMAX Astra 1220S.
> When I scan a normally exposed slide, it comes out quite dark, and
> I must stretch the histogram in XSANE (GAMA=1.3 B=120 C=120 for example)
> This causes 'holes' in the output histogram (the dark values go 0, 7,
> 11, 15...). So it may be desirable to scan internally with 12
> bits/color, even if the output is only 8 bits - to provide 'meat' for
> histogram stretching.
the preview is always done with 8/24bpp.
If you select "use custom gamma table" the real scan is done with full
bit depth (12/36 bpp for the Astra 1220S) and the gamma correction
is done with a transformation from 36->24bpp in the scanner.
> Increasing the exposure time would help here (in the dark areas) but
> would probably cause overflow in the bright pixels.
The Astra 1220S does not support change of the exposure time.
> 1. at each scanhead position take several readings and average them
> before moving the scanhead on.
This can not be done in the sane backend because the scanner controls
the movement of the scanhead.
> 2. run several full scans (running the scanhead back and forth across
> the scan area). (smpling only when moving forward)
This would not be a backend function, this should be done in a frontend.
I will add it as "may be one day" to the end of the todo list of xsane.
But I am not sure if it will ever come.
But a suggestion:
xsane is able to auto-increase the file name counter.
Scan an image n times as image-01.pnm to image-nn.pnm
Write a tool that reads image-01.pnm to image-nn.pnm
and does average and save it to image.pnm
-- Homepage: http://www.wolfsburg.de/~rauch sane-umax: http://www.wolfsburg.de/~rauch/sane/sane-umax.html xsane: http://www.wolfsburg.de/~rauch/sane/sane-xsane.html E-Mail: mailto:Oliver.Rauch@Wolfsburg.DE
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