Digital BW, The Print

That's what I used to think and do, too, but very recently I changed my
mind. 
These days I'm scanning Portra400BW 6x7 with an Epson3200 using Vuescan, and
my very simple workflow was to get a raw scan, extract the green channel and
Photoshop away, setting BP and WP etc.
I was a bit concerned, though, on the huge amount of stretching I had to do
setting BP/WP in order to bring the usually *very* flat scan to cover the
whole 0-255 range, but given that I was starting from the raw scan, I
thought I had no control over it. I was wrong: I found that the automatic
exposure set by Vuescan is, at least with this film-scanner combination,
usually way too short: talking Vuescan numbers, the automatic setting is
just below 4, the optimal setting ranges from 6 to 11 (you can verify/change
this number by checking the Lock exposure checkbox at the bottom of the
Device tab: the value is set after the preview).
I used to think that increasing exposure would only shift the histogram
curve from the light to the dark end, but it's not true. Assuming that the
response is linear (I'll stand corrected on this: Austin, your knowledged
opinion is?), if exposure x gives a 20-100 range, exposure 2x gives 40-200,
thus resulting in a less flat scan. The result is a smoother image (nothing
outstanding, but noticeable), especially after steep curves and levels (e.g.
to bring dull skies to life).
Bottom line, my workflow now includes a little extra step at the begininng,
which is one or more 100dpi scan, checking the resulting histogram in
Vuescan, with a locked exposure, until I get a reasonable range.
 
Alessandro Pardi

-----Original Message-----
From: Kevin Gulstene [mailto:kevin@...]
Sent: Tuesday, May 27, 2003 5:11
To: DigitalBlackandWhiteThePrint@yahoogroups.com
Subject: [Digital BW] Re: Scanning


Craig-

Everything downstream from the raw data from the A/D is software  
manipulation.  There is nothing you can do in a single scan to extract  
more real additional information.  No tweaks, no special techniques.  
What is on the film is in the raw scan file.

<snip> 

I use vuescan the same way Bob  described his use.  Set the white and  
black clipping points at 0 and import it.  I get a nice smooth  
histogram with all the relevant information - the scan is usually quite  
flat though.

--
Kevin Gulstene




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