Re: filmscanners: This Gamma Thing...?

["shAf" <michael@shaffer.net>]

Stephen writes ...

> Tony, for us users of Vuescan on a Mac scanning for output to an
Epson
> Printer, would 1.8 be good gamma starting point?  Vuescan defaults
to 2.2,
> I'm guessing because most users are on Windows.
> ...

    A 2.2 gamma space has only two things going for it (... 3 if you
create images for the wwweb ...).  (1)  It is closer to native monitor
spaces, so therefore will not be as reliant on your monitor's
"characterization" (or calibration) being absolutely perfect. (2)  It
is said to be more "perceptually uniform", which means a 10%
adjustment in the shadows is similar to the same degree of adjustment
in the midtones and highlights ... which makes adjustments more
predictable and intuitive throughout the tonal range.
    What gamma=2.2 has going against it is ... it is a more distant
throw from a gamma conversion from (e.g.) gamma=1, or some devices
which have a native gamma near 1 (for example, I gather some scanners'
native (or raw) gammas are considered unity).  This "distant throw"
from 1 to 2.2 is a bit of a stretch for an 8bit conversion, but not
too big a deal if done in highbit space (the normal practice).  A
gamma space of 1.8 is probably nearer that of most printers as well.
    My summary would be ... if you want a more predictable editing
space, you should use gamma=2.2, but if your scans tend to go straight
from scanner to your printer with minor adjustments, then gamma=1.8
cannot be a wrong choice.

my US$0.02  ... shAf  :o)