filmscanners: Vuescan trials

["shAf" <rarewolf@roadrunner.nf.net>]

  I appreciate using Vuescan for many reason, but I have to admit ...
sometimes its behavior is inconsistent and confusing.

  Using version 7.1.9, I wanted to setup Vuescan for a general exposure and
for scanning many frames of Supra 400.  I wanted to use auto-exposure of a
representative frame to determine the general manual exposure settings ...
and then wanted to include the non-exposed part of the film with "auto-mask"
for determining manual mask settings.  I am a bit confused with the results.

  Loading default settings and setting appropriate parameters for negative
film (Kodak/Supra/400), and scanning a full represenative frame (with reds,
greens, blues, plenty of "white", and deep shadows) resulted in the
following "auto mask" values:

R =.948
G =.705
B =.725

  ... values which imply "orange".  However, if I now choose "manual
expose", and scan a frame which includes non-exposed film, I get these "auto
mask" values:

R =.995
G =.920
B =.969

  ... not very orange at all.  However, both settings for the mask resulted
in acceptable images given the same "color" settings ... I have no idea
which settings were optimal, and I don't know how to interpret the second
set being so close to a neutral shade, but want to believe they were the
better determined set.

  Lastly ... the IR exposure was automatically determined to be 2.24.  At
the time I thought this was a bit high (previous experience with earlier
versions of Vs usually implied IR exposures near 1), but decided to check
later and after a final scan.  Indeed, when I asked Vs to deliver a 16bit IR
Tif and scanned from memory, it delivered a nearly white image with a few
gray defects.  I thought this should be closer to generally neutral gray so
that defects could show as "dark" or "bright".  But it seems I cannot
experiment with manual IR settings ... even when using similar exposure
values I cannot duplicate the "white" over-exposed IR ... but instead get
very dark grayscale images in spite of my exposure values ranging between
1.0 - 3.0 ... weird!!!

  (Ed ... if you want me to create a log file and submit it to you, please
give me a brief desciption about how ... and whatever else you might need)

shAf  :o)