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[OM] We're behind the times

Subject: [OM] We're behind the times
From: Paul Wallich <pw@xxxxxxxxx>
Date: Tue, 18 Jan 2000 15:33:32 -0500
At http://www.scitex.com/aboutus/press/english/leafcmost.htm
there's a press release from Scitex, the high-end scanner people,
on their new 6.6 megapixel sensor specifically designed for a
24x36mm frame and modified SLR backs. They anounced a week ago...
(That's approximately 2100x3150, which should be fine for most
purposes -- 14x21" at a nominal 150-line screen.)

What's interesting to me is that the new generation of sensors
appears to be going with a larger pixel size than previous generations.
The current 1600x1200 2/3" sensor has about an 8.47-micron pitch.
The new 3.3-megapixel sensors have about and 11-micron pitch, and the
Scitex has an 11.43-micron pitch. This sort of makes sense with the
notion that earlier sensors had been bumping up against optical limits:
8 microns is all of 10 wavelengths of red light (or essentially equivalent
to 65 line pairs/mm resolution). But more important, with the short lenses
required by the smaller sensors, any serious stopping-down gets you into
bad diffraction karma -- I went back to my high school physics text, and
it claims that for a 0.6-mm aperture (about f11 for a 6.5mm lens) the
central diffraction spot comes to 1.17 milliradians for red light (700 nm)
which for a 2/3" sensor implies a maximum real resolution of about 1370
pixels.

So if the Scitex or the next generation of CCD is priced where I can afford
it, I hope there's an OM back. The new generation of PCMCIA adaptor supports
data rates of 30-50 megabytes per second, so maybe we'll start seeing 10 or
12 bits per pixel, and so forth.

paul

Paul Wallich                                            pw@xxxxxxxxx



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