Re: filmscanners: Vuescan - A few technical questions

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

Joel writes ...

> For Ed Hamrick (most likely):

    I'm going to throw my own observations in here and hope Ed
addresses them as well.

> ...
> 1.  In the Color balance tab, what is the difference between
"Neutral" and
> "Auto Levels?"

    If you use auto levels, and after the scan is done (you can 'scan
memory' without creating any files) ... you inspect the whitepoint
values by unchecking "auto whitepoint", you'll see different values
determined as best by VS.  Presumably if you had used "neutral" these
values would be identical.
    I've never had much luck with "neutral" ... BUT if I change the
differing RGB whitepoint values, as determined with "auto", to
something representative of all three but equal (e.g., an average of
the three), I get something entirely different.  I've cured some
improper hues with the latter method, whereas I wasn't happy with
using "neutral".
    I use "auto levels" ... but it seems I always involve myself with
playing with the automatically determined values, usually making them
equal and nudging them only slightly.  These whitepoint values can
affect the resulting "crop" quite a bit.  Use them together with
brightness and gamma to get your scan just right before you create the
final TIFF.  I usually 'scan memory', while creating low res JPEGs ...
inspect them in Photoshop, and when I finally like what I see, I crop
to the final full res TIFF.

> 2.  Also in Color balance, does "White balance" assume that the
lightest
> object in the image is white?  Can it be used if there are no white
objects
> in the frame?

    Experiment with this and let us know what you settle with.  Which
scanner are you using??

> 3.  When should Options/Long scan not be used.  I assume it is
useful for
> bringing out shadow detail, but it seems to me that it would always
be good
> to use, since "auto exposure should control blowout.  Are there
situations
> where it might cause problems?

    I realized for my LS-2000 Coolscan, the 2nd pass would not
properly register with the 1st ... bummer!! ...

> 4.  How does Vuescan calibrate the scanner?  When I pull down
"calibrate"
> from the device menu, nothing seems to happen.  Don't you need an
IT8 target
> or equivalent to calibrate a scanner?

    Only some scanners can use this feature ... but it has nothing to
do with a reference target ... more to do with measuring where in the
frame senisitivity to light changes.

shAf  :o)