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High resolution scanning



Steve Russell of Philips has kindly pointed out that I told not quite all
of the story in my recent postings about film resolution scanning.

The point I was making was that film dyes have the same sized lumps of
colour whether the material is sliced to be 35mm or 16mm wide, so to get
the same resolution into the digital world you need fewer pixels from 16mm
than you do from 35mm.

Steve's point - which is perfectly correct - is the converse. If you
arrange the optics of the film scanning system such that you use the same
number of pixels in both film gauges, then you get a higher resolution scan
in 16mm. In the specific case of Spirit, the 16mm gate uses the full 1,920
pixels of the CCD block, and so, in terms of resolving power, is actually
more than twice as good as 35mm. Super 16mm has a frame width of about
12mm, divided by 1,920 pixels, divided by 2 for Nyquist, is up around 80
pairs per millimetre, which is very good.

Dick Hobbs

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