Re: filmscanners: VueScan Histogram

[Julian Vrieslander <julianv@mindspring.com>]

I will add my vote to those VueScan users who do *not* want it to become 
an image editing application.  I would rather do my tweaks in Photoshop.

But I do encourage Ed to continue development of features which enable 
VueScan to save files with the best possible bits.  I think a histogram 
display is useful for this.

With the current version of VueScan I need to set the white point and 
black points by guesswork.  I pick a pair of percentage numbers and hope 
for the best, or if I have time, I will do a few Prev Mem or Scan Mem 
trials to see the effects of various settings.  But often, when I bring 
the scan into Photoshop and check the histograms, I discover that I 
chopped off the highlights or shadows.  Or I might have set VueScan's 
limits too conservatively, and there are a lot of empty bins in the 
histo, with the image data squished into a narrow range of tonal values.

Maybe with more experience I will get better at inspecting VueScan's 
displays and choosing the right values for WP, BP, and gamma.  But since 
these displays are not color managed, I also have to mentally compensate 
for how the image appearance is going to change when it goes into 
Photoshop.  That's a lot for my poor addled brain to handle.

A histogram would help, because the shape of the data distribution is 
often more informative than the clip percentages.  Ideally, VueScan would 
have the tried-and-true histo interface which provides draggable markers 
for WP, BP and gamma, with live image updates.  But I know Ed does not 
like to spend a lot of time implementing complex UI elements that require 
platform specific code.  If Ed retains the numeric entry UI, I suggest 
that the histogram has a calibrated axis for levels (e.g., 0-255 for 8 
bit data) and that the WP and BP can be entered using values from this 
axis (rather than percentages). 

--
Julian Vrieslander <mailto:julianv@mindspring.com>