jeff miller wrote:
I'm converting my old analog scanning electron microscopes to digital/pc
based.

One of the important questions is how many bits of resolution ie: levels
of greyscale are required. I've heard the analog front ends of the
scopes have a maximum SNR of about 72 dB, or 12 effective bits, and to
give me some flexibility for digital image processing that's about what
I'll shoot for: a bit better if I can get it.

But on the other end of the scale, I'm wondering what are accepted
figures for signal to noise or dynamic range of various display
technologies, and of the human eye.

It seems to me the published "contrast" figures for LCD displays of
about 600:1 peg them at about 49dB dynamic range.

What is generally accepted for B&W film? Is it highly dependent on film
type and processing? Anyone know some typical figures for various
processes? Is "silver print," which in my mind is marked by high
contrast, a special technique or just a fancy word for black and white?

How about for CRT's? Deos it depend in part on the design and
construction of the CRT, and do dedicated monochrome CRTs have a greater
dynamic range for greyscale than color CRT's used to display greyscale
images?

And what about the human eye, for that matter? It's been suggested the
human eye has only about 6 bits or 36 dB dynamic range/SNR for greyscale
images. Is that about right? Bonus question: I know the sensitivity of
the human eye varies with color, being most sensitive at about 555 nM
green. How about dynamic range and SNR? Deos it vary with color, too?

Man! you ask a lot of good questions! I suspect that many of the answers
are to be found in papers of the SMPTE.

I recall that the contrast between printer's ink and glossy paper is
about 10:1 and B&W prints on glossy paper are a bit better (but on
matte, a bit worse). The contrast ratio of newsprint can be as low as
3:1 before the ink starts to look gray. Discouraging, no?

Look at your TV screen when the set is off. No part of it gets darker
when the set is on, but it sure looks like it does.

Jerry
--
Engineering is the art of making what you want from things you can get.
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