[Leica] More scanner info (Minolta Dimage Dual Scan III)

[Martin Howard <mvhoward@mac.com>]

A few more impressions after yet another few days with this scanner, 
along with some tips.

I tried the VueScan software, but decided against it (as mentioned in a 
previous email).  However, one of the things it has which the Minolta 
bundled software doesn't have (but VueScan does) is a clipping preview. 
  In other words, it colour codes those pixels which are clipped at 
either end of the spectrum.

I've discovered that you can twiddle around with the Curves tool in the 
"DS Utility" program to accomplish much the same thing (actually, it's 
even more useful). To see where the highlights are, go to "Image 
Correction" and pull up the "Curves" tool (first one). Then adjust the 
shadow point until it is a few units within the highlight (i.e., you 
have an almost vertical line at the highlight end of the curves 
display). Pixels that remain non-black show you where the highlights 
are.  By sliding the shadow point back-and-forth, you can get an 
impression of where the information in the highlights is.  You can also 
move the "levels" triangles, or enter numerical values (I usually just 
plug "253" into the "shadow" input box).

To do the same for shadows, move the highlight point towards the shadow 
end of the scale, thus creating a vertical line on the shadow side.


Sometimes it is difficult to get scans that cover both highlight and 
shadow detail from a negative.  A two-pass scan method helps, although 
I seem to remember reading somewhere that you're not actually extending 
the dynamic range... but the results look better in any case.  In 
particular, the mid-tones seems to be smoother and exhibit less noise.  
In the past two days, I've found a much better way of recombining the 
images rather than using the "Curves" tool in PS.

Scanning one image overexposed (overly light, calling it Hi) and one 
image underexposed (overly dark, calling it Lo), open both in Photoshop 
and select the Hi image as the one you're working on. Do "Image->Apply 
Image". Select "Lo" as the source, "Darken" as the blending mode and 
play with the opacity until it looks about right (between 60% and 80% 
seems right most of the time for the images I use). Use the Eyedropper 
tool in combination with the Info palette to check levels and dynamic 
range.  Unfortunately, this only works with 8-bit images, but it's 
still pretty useful.


BTW -- speaking of VueScan: the evaluation copy, that is the version of 
the software that you get before you pay the $40 registration fee, 
prints big "$" signs over your image when it saves the JPEG or TIFF 
files to disk.  Which makes evaluating the scanned images absolutely 
impossible, because you cannot see much of the underlying image.  Sort 
of defeats the whole purpose of shareware, me thinks...


And one final tip: If you use Photoshop, get the book "Real World 
Photoshop 7" (exists in a version 6.0 too).  It's worth every single 
cent of the $49.95 cover price, especially when you buy it for $34.95 
at Amazon... ;)

M.

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