Can anyone explain the value, or reliability of this procedure as stated
in the Vuescan Help file in view of my following experience:-
I needed another scan of a negative that I had scanned a few days ago. I
went through the same procedure as I had done then of scanning the same
unexposed leader of the film and used the settings to scan the required
frame. The resulting scan differed significantly from the previous scan.
I then made three continuous scans of the same frame of the unexposed
leader with the same settings for black point, white point, colour
balance, clipping exposure etc. etc. for the scans.
The scans using a Dimage Scan Dual 11 scanner produced different
readings:-
RGB Exposure readings were 2.004, 2.086, 2.098 respectively.
Base color Red - 0.778, 0.748, 0.744 respectively.
Base color Green - 0.77, 0.732. 0.732 respectively.
Base color Blue - 0.646, 0.622, 0.616 respectively.
Using these setting for the scan of the exposed negative produced scans
that differed significantly from one another.
What's the point of using the advanced workflow suggestion if it does
not produce the same result from the same unexposed leader?

Bill Capp.

Hello, Tommy T
you wrote...

Scanner light source changes slightly during warming up. May be this is
the reason for different exposure values. If you want reliable results
you should wait some time before you scan.

The film base color values depend on (and vary with) the exposure
settings. As long as the ratio between the RGB values is the same
everything is ok. This ratio does not change very much in your example.

Color balance=neutral? In my experience film base color values have to
change in 0.1 steps to see a difference. 0.01 steps are not visible at
all...

You can use an average of all measured values. And you can correlate
them with exposure settings and then manually choose settings from a
list.

--
Erik Krause
Digital contrast problems: http://www.erik-krause.de/contrast

Erik Krause <erik.krause@gmx.de> wrote in message news:<MPG.197d246c5166d6c098a113@ID-18456.user.dfncis.de>...

I agree 100%.
I act this way since some months and finally found consistent results.
Obviously, when you crank up the exposure very much (dia) o crank down
very much (neg), film base color becomes 0.999 0.999 0.999, so you
have to build the "base color/exposure" table only for values not much
distant from base exposure.

Fernando