What are accepted figures for signal/noise (SNR) and dynamic rangefor CRT? LCD? Film? Human eye?

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?

Thanks!

-Jeff

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

--snip--

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?

Most of what you ask I don't know, but what I _do_ know is this:

In infrared imaging (which is what I'm familiar with) you take as many
bits as you can get at the sampling rates you need -- this is currently
14 bit ADC's at 10MHz on high-end systems. Even so you need some
up-front gain selection (in the form of allowing the user to select a
few different integration times) to get the best picture for the
conditions. This data gets processed, gained up linearly or
non-linearly, possibly spatially and/or temporally filtered, then
presented to the user on video with an 8-bit DAC. Needless to say you
throw away a _lot_ of information when you go through the
user-presentation layer.

--

Tim Wescott
Wescott Design Services
http://www.wescottdesign.com

I am not certain about the technical data, you should ask some electronic
engineer, but it's very difficult to construct a lcd or tft scrren that can
compete a good crt, because the picture in the crt is made by tiny bits of
phosphorus struck by the cathod rays, also emitting their own light.Besides
that, crts have a developing history of more than 50 years.

--
Tzortzakakis Dimitri?s
major in electrical engineering, freelance electrician
FH von Iraklion-Kreta, freiberuflicher Elektriker
dimtzort AT otenet DOT gr
? "jeff miller" ?????? ??? ??????
m...
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?

Thanks!

-Jeff

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.
¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯ ¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯

Jerry Avins wrote:

...

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

Correction: 30:1.

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?

Typical newsprint before the now-common biodegradable soy ink was 10:1.

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

"Jerry Avins" wrote

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

Correction: 30:1.

Photographic paper can get to 2.0 od reflected, a range of 10 ^ 2 = 100:1.

I just took a measurement from a printed page on coated stock, it
yielded 1.27 = 1.3 = 10 ^ 1.3 = 20:1.

--
Nicholas O. Lindan, Cleveland, Ohio
Consulting Engineer: Electronics; Informatics; Photonics.
To reply, remove spaces: n o lindan at ix . netcom . com
psst.. want to buy an f-stop timer? nolindan.com/da/fstop/

Nicholas O. Lindan wrote:
"Jerry Avins" wrote


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

Correction: 30:1.


Photographic paper can get to 2.0 od reflected, a range of 10 ^ 2 = 100:1.

I just took a measurement from a printed page on coated stock, it
yielded 1.27 = 1.3 = 10 ^ 1.3 = 20:1.

Thanks for the reality check. The 30:1 figure was the best available,
typically found in (new) eye charts and photographic resolution targets
when I played with that stuff 40 years ago.

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

Nicholas O. Lindan wrote:

"Jerry Avins" wrote


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

Correction: 30:1.


Photographic paper can get to 2.0 od reflected, a range of 10 ^ 2 = 100:1.

I just took a measurement from a printed page on coated stock, it
yielded 1.27 = 1.3 = 10 ^ 1.3 = 20:1.

Unless print paper has changed in the twenty-five years since I made
some of those measurements, paper doesn't quite get to 100:1. I have
seen papers with blacks at 2% (50:1). Most papers have about 3% black
reflectance, however (33:1)

At one time I worked on a project finding black coatings for cameras and
other EO sensors. It is amazing how hard it is to get a truly black
black. Even the famed 3M Black Velvet was a 2% reflectance. The only
thing we found was a coating by Martin Marietta that was close to 1%.

The emulsion itself in photographic paper is what creates that
reflection, regardless of how much black silver it has in the emulsion.
I would assume in inkjet ink it would be the binder that holds the
pigment or dye to the paper. With laser printers the toner has some wax
in it.

Don Stauffer in Minneapolis wrote:
Nicholas O. Lindan wrote:

"Jerry Avins" wrote


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


Correction: 30:1.



Photographic paper can get to 2.0 od reflected, a range of 10 ^ 2 =
100:1.

I just took a measurement from a printed page on coated stock, it
yielded 1.27 = 1.3 = 10 ^ 1.3 = 20:1.

Unless print paper has changed in the twenty-five years since I made
some of those measurements, paper doesn't quite get to 100:1. I have
seen papers with blacks at 2% (50:1). Most papers have about 3% black
reflectance, however (33:1)

At one time I worked on a project finding black coatings for cameras and
other EO sensors. It is amazing how hard it is to get a truly black
black. Even the famed 3M Black Velvet was a 2% reflectance. The only
thing we found was a coating by Martin Marietta that was close to 1%.

The emulsion itself in photographic paper is what creates that
reflection, regardless of how much black silver it has in the emulsion.
I would assume in inkjet ink it would be the binder that holds the
pigment or dye to the paper. With laser printers the toner has some wax
in it.

I once got down to about 0.2% edge-on to a stack of single-edge razor
blades with the backs removed. (I was puzzled at first by poor
performance, but it worked like a charm after being degreased.) That's
about what one gets with a Tyndall tube*. I still have a can of 3M's
Nextel Velvet Black, but as far as I know, they don't make it any more.
(Nextel now means something else.) Kodak's Brushing Lacquer was pretty
good, too, but I think that's also a thing of the past. I'm almost out
of Edmund's flock paper, but that's still available.

Jerry
__________________________________
* I found no web reference to a Tyndall tube, so I figure a brief
description is in order. Tyndall needed a good light absorber for his
ultramiscrope, http://tinyurl.com/66e63 He drew a piece of glass tubing
-- a side tube on his specimen chamber -- to a cone that curved like the
toe of a jester's shoe. The outside of the tube was coated in soot from
a candle flame. Light entering the tube is reflected deeper and deeper
into the small end, suffering a small loss at each reflection.
Eventually, a ray turns around and starts out, again reflecting many
times. By the time it emerges, all those slight absorptions have pretty
well attritted it to zilch.
--
Engineering is the art of making what you want from things you can get.
¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯ ¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯

"Don Stauffer in Minneapolis" wrote
Nicholas O. Lindan wrote:
Photographic paper can get to 2.0 od reflected, a range of 10 ^ 2 = 100:1.
Unless print paper has changed in the twenty-five years since I made
some of those measurements, paper doesn't quite get to 100:1. I have
seen papers with blacks at 2% (50:1). Most papers have about 3% black
reflectance, however (33:1).

It is a non-specula measurement. 2.0 isn't hard to get to. However,
2.0 is not a good value for making prints with any shadow detail as
it is up on the shoulder. 1.8 OD is a better max value, closer to
2%, as you indicated.

At one time I worked on a project finding black coatings for cameras and
other EO sensors. It is amazing how hard it is to get a truly black
black. Even the famed 3M Black Velvet was a 2% reflectance. The only
thing we found was a coating by Martin Marietta that was close to 1%.

Not only isn't it black, it's yellow, or blue or red ... Black, like
white seems to be an imaginary concept.

--
Nicholas O. Lindan, Cleveland, Ohio
Consulting Engineer: Electronics; Informatics; Photonics.
To reply, remove spaces: n o lindan at ix . netcom . com
psst.. want to buy an f-stop timer? nolindan.com/da/fstop/