S
Steven Woody
great! this reply is just what i need. thak you Roger. it seems that
i've not found the exposure setting as you described in the SilverFast
SE and i am concidering switch to Vuescan.
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woody
great! this reply is just what i need. thak you Roger. it seems that
i've not found the exposure setting as you described in the SilverFast
SE and i am concidering switch to Vuescan.
-
woody
R
Roger S.
"The Perfection 4990 also offers automated options for those that want
to get good results quickly and simply. There's Auto Exposure in both
the home and professional modes of the Epson Scan driver, and
SilverFast SE offers automated exposure settings, as well as automated
controls for dust removal. In either application, you can opt for more
powerful manual controls."
http://reviews.cnet.com/Epson_Perfection_4990_Photo/4505-3136_7-31319257.html
It's gotta be there somewhere.
F
false_dmitrii
If I try to get technical I'll just make lots of big mistakes, but I'm
pretty sure CSM1 is the one to listen to in this thread. It's fully
possible for a scanner to make hardware adjustments to light strength,
sensor gain, and exposure time. How exactly this is done is no doubt
different between models, but the goal is the same as with cameras,
getting a good midrange exposure with as little highlight blowout as
possible. My sense is that consumer-oriented scanners tend toward
fully auto hardware exposure, just like point-and-shoot cameras. My
Epson 4870 has no obvious analog gain controls in its software. It's
been said in this group that there *are* discrete lightsource
steppings in place, and that Vuescan can be used to invoke them
manually. My film scanner has 3 gain controls in its driver, one per
RGB channel. They have a concrete effect on the exposure quality of
the initial output even if no software adjustments are applied.
It's also common to have an "auto" button in the driver that applies
purely software adjustments to the initial scanner output in a "level
adjustment" game, as you put it. It's even possible to have a mix;
someone wrote here that adjusting the Epson driver's white and black
points in prescan has the potential to bump the scanner to a more
appropriate light strength during the final scan. How exactly this is
implemented again depends on the scanner in question. If there's no
discrete gain control or "lock exposure" option in the driver, you'll
have to try Vuescan for hardware control or accept some amount of
software adjustment in your driver's output.
You should be able to test your driver's hardware behavior by scanning
different-toned images. Try something that's mostly white, then try
an all-black page. Use a high-res setting to see if there's a
measurable difference in scan times. See whether the data *prior* to
level adjustment is distributed as far to one side of the histogram as
you'd expect with a fixed exposure. You can also try blocking your
scanner's calibration area with something darkish prior to powerup to
see if it causes long scan times and overexposures. Or try other
things I can't think of.
Whatever else, if you turn off everything "auto" and limit your driver
interaction to setting an appropriate white point (note that I mean
setting the "brightest" WP in the luminance histogram, not sampling a
WP to balance colors), you should get as close to an unadjusted scan
as you're likely to find useful.
false_dmitrii
R
Roger S.
I don't think that the scanners are varying the light source or
aperture, leaving us with exposure time.
This would be more useful for slides than negatives- see if you can
trick it into increasing exposure.
I think that's reasonable. Consider using software that gives more
obvious control over exposure and see if it makes a difference.
Roger