[rollei_list] OT:Epson scanners focus point
- From: CarlosMFreaza <cmfreaza@xxxxxxxxx>
- To: rollei_list@xxxxxxxxxxxxx
- Date: Thu, 26 Nov 2009 14:43:31 -0300
A few minutes ago I found an interesting Epson document, it says that
newest Epson scanners from the Perfection and GT series use a fixed
focus optics system, the fixed focal point is _just above the surface
of the glass for optimized film scanning_, it means on the glass.
Epson highest end graphics arts scanners use an Auto-Focus optics
system that can be used in AutoFocus mode or manual mode (very useful
for 3D objects scanning). The document says that when you scan slides
mounted in holders, _you can set the focus for super sharpness to
compensate for the 2.5mm distance between the glass and the slide_, it
means again that the best focus is on the glass directly.
Epson v700 and v750 also have fixed focus optics system, they do have
two lenses, but they have to do with the scanning resolution and not
with the focusing system.It means again -according the Epson document-
the best focusing point for these scanner are on the glass too.
Anyway film holders are necessary in spite of the fixed focal point on
the glass to avoid Newton rings, to maintain the film flatness and to
put the film in the right scanning position quickly, but the
conclusion is that closer the film to the glass bed, sharper the
scanning in theory for the Perfection and GT lines.
I wrote in other forum I couldn't see a real advantage scanning on the
glass except for dark slides or negs, etc., but I did not write that
scanning on the glass produce worse results than with the film holders
and then I tend to believe that the Epson document is very right,
perhaps I don't see the difference clearly because most of the times I
scan on the glass directly the film is not perfectly flat and with the
holders it is flat, but it's more than interesting to know where is
your scanner fixed focal point exactly:
http://ftp.epson.com/pdf/exp16_/exp16_ts.pdf
(Page 6 is about the focus method)
Carlos
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