VueScan - Exposure on Epson scanners

  • Thread starter Lorenzo J. Lucchini
  • Start date


Lorenzo J. Lucchini

I have been trying to understand what "exposure" means to VueScan when
working with Epson scanners (I own an Epson RX500).

An old thread mentions the ESC L command, which Epson dubs

Other posts say that VueScan's exposure is "fake" in case of (most)
Epson scanners, in that it simply tells the scanner to change a
look-up table (change gamma?).

Then, apparently, using the ESC Z command to change gamma (there are
two formats for this command, a short and a long one, right? which one
is it?) does actually change the exposure time the scanner uses.

So, what does VueScan currently do?

If it uses the ESC Z command, my understanding is that the exposure
time will change, but then the raw data output by the scanner will be
modified using a non-linear LUT. Correct? Is there a way around this
that allows obtaining a really raw (not modified in any way) scan with
an arbitrary exposure time?

Does anything change in the above depending on whether 8-bit or 16-bit
color channels are used?

Also, I see no mention of the ESC L command in VueScan's logs; does it
actually do anything useful?

by LjL
(e-mail address removed)


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