HvdV said:
I've never opened a flatbed scanner, but it would seem reasonable that
if the lenses have appreciable focal length variation then there is a
calibration screw near the lens to factory-tune the focus. If so, then
one could improve calibration with that instead of pieces of cardboard.
Anyone looked inside a V700 yet?
-- Hans
Typical setups have a plastic molding with a U shaped bed that
holds the cylinder shape of the total lens while a flat metal
spring clamps the lens assembly in that bed. The lens can
still be shifted for focusing over the length of that bed in
the manufacturing process and is then fixed with some glue. It
will be difficult to get near the lens anyway as it halfway
the folded path of 4-5 mirrors between the scan bed and the
linear sensors.
With the V700 and the V750-M there's another aspect. The wide
lens that does the scan bed for A4 reflective and 8X10 film at
4800 SPI will be focused just above the glass of the scan bed,
most likely 0.5 mm above to take care of some manufacturing
tolerances and the expansion of the scanner housing when it
gets warmer after some scans. At least that's something I
would think off if I was an Epson designer. That should ensure
that there's no chance of having the focus way below the glass
+ it takes care of having the focus closer on the film
emulsion in a film scan. For reflective scanning at 600 SPI
the right focus is far less important. I think Epson's
priority lies in getting that focus more or less correct for
the 8x10 film. The two lenses may have had a focus alignment
to one another on a bench before the assembly of the total
optical carriage (sensor, mirrors, lens) is placed in the
scanner. The height adapters should bring the film holders at
the right focus for the 6400 SPI lens, that's what the user
adds to the job.
http://www.i-love-epson.co.jp/products/colorio/scanner/gtx900/technology.htm
Ernst
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Ernst Dinkla
www.pigment-print.com
( unvollendet )