[sane-devel] EPSON 3490, calibration and raw data

Levente Novák lnovak at dragon.unideb.hu
Sun Feb 19 16:19:37 UTC 2006

On Sun, 2006-02-19 at 15:48 +0100, Krzysztof Halasa wrote:

> It looks like the black calibration (lower values, around 70) is the same
> data in both 8-bit and 16-bit mode (i.e., in 8-bit mode the LSB is
> present and 6-bit MSB is assumed to be zero).
> I will experiment with this a bit longer - probably someone has an idea
> how to set 16-bit gamma tables and/or to set "analog" gamma value (to
> 1.0) so the scanner doesn't modify the data?
> Or maybe it's already transparent, i.e., the scanner does no gamma
> but just brightness and contrast (already set to 128 = neutral)?
> The peak values are a bit different from the 14-bit calibration
> data * 4, the range should be something like 280 - 60500.
> -- 

I am myself very interested in what you are currently trying to achieve.
If I can help you or Oliver with some tests (I own also a PF 3490),
please don't hesitate to write me!

Do you know whether this scanner sets a different focal plane when
scanning slides/film compared to the flatbed (as it should)? One very
important aspect in film scanning is to have the material exactly in
focus. Higher-end scanners can adjust their lens accordingly.

Also, I am not convinced we should always follow the Windows driver to
the letter. I mean maybe the hardware is capable of more than the
windows drivers are programmed for. Low-end scanners are marketed and
sold with shallow profit margins, that's why they often lack data/spec
sheets and their drivers are not always as elaborated than those of
their bigger cousins.


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