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#21
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jim wrote:
... If your next question is - Is it spelled "grey" or "gray"? I don't know :} ... Both are used, but "grey" is used less. The disappearance of "gaol" in favor of "jail" is now nearly complete :-) Jerry -- Engineering is the art of making what you want from things you can get. ŻŻŻŻŻŻŻŻŻŻŻŻŻŻŻŻŻŻŻŻŻŻŻŻŻŻŻŻŻŻŻŻŻŻŻŻŻŻŻŻŻŻŻŻŻŻŻŻŻŻ ŻŻŻŻŻŻŻŻŻŻŻŻŻŻŻŻŻŻŻŻŻ |
#22
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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. |
#23
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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. ŻŻŻŻŻŻŻŻŻŻŻŻŻŻŻŻŻŻŻŻŻŻŻŻŻŻŻŻŻŻŻŻŻŻŻŻŻŻŻŻŻŻŻŻŻŻŻŻŻŻ ŻŻŻŻŻŻŻŻŻŻŻŻŻŻŻŻŻŻŻŻŻ |
#24
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"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/ |
#25
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jeff miller wrote:
Roger N. Clark (change username to rnclark) wrote: jeff miller wrote: This thread is providing some very useful information about SNR of media and human eyes... keep it coming! See: Notes on the Resolution of the Human Eye How many megapixels equivalent does the eye have? The Sensitivity of the Human Eye (ISO Equivalent) The Dynamic Range of the Eye The Focal Length of the Eye: http://www.clarkvision.com/imagedeta...esolution.html Contrast thresholds data: http://www.clarkvision.com/visastro/omva1/index.html Roger Great resource. Based on that data, I'd conclude that images captured from my microscope might benefit for 65K x 65K resolution, so I'll use 16 bit D/A's to drive my scanning coils. Of course that kind or resolution can only be rendered in print. And represents an 8GB file size. And will take 2 hours to collect.... but might as well build it in. The figure of 10,000:1 dynamic range in any "one view" corresponds to about 12 bits. That's pretty much exactly the nominal dynamic range I've heard quoted for the front end of an SEM. But it might seems no current reproduction technology acheives quite that. -Jeff Ooops, 10K:1 is more like 13.5 bits. But I'm finding a wide range of figures online for dynamic range of the human eye. I visited Barco's website in hopes of finding contrast figures for CRTs and in a white paper comparing CRT and LCD displays, I think they tossed out a figure of 100:1 for the human eye. 1,000 to one has been mentioned here as well. The site referenced above so far holds the title for claiming the widest range. The white paper also tossed out a contrast figure for CRT's of 3,000 to one, about 11.5 bits. The human eye figure of 100:1 is the most surprising. The low contrast of film is also surprising. I guess it (re film) shouldn't be, I know that MgO is the most reflective substance as far as diffuse reflectors go. I forget the figure. -Jeff |
#26
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jeff miller wrote:
... The human eye figure of 100:1 is the most surprising. The low contrast of film is also surprising. I guess it (re film) shouldn't be, I know that MgO is the most reflective substance as far as diffuse reflectors go. I forget the figure. Photographic paper is often coated with barium sulfate -- baryta -- under the emulsion. Jerry -- Engineering is the art of making what you want from things you can get. ŻŻŻŻŻŻŻŻŻŻŻŻŻŻŻŻŻŻŻŻŻŻŻŻŻŻŻŻŻŻŻŻŻŻŻŻŻŻŻŻŻŻŻŻŻŻŻŻŻŻ ŻŻŻŻŻŻŻŻŻŻŻŻŻŻŻŻŻŻŻŻŻ |
#27
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jeff miller wrote:
jeff miller wrote: Roger N. Clark (change username to rnclark) wrote: jeff miller wrote: This thread is providing some very useful information about SNR of media and human eyes... keep it coming! See: Notes on the Resolution of the Human Eye How many megapixels equivalent does the eye have? The Sensitivity of the Human Eye (ISO Equivalent) The Dynamic Range of the Eye The Focal Length of the Eye: http://www.clarkvision.com/imagedeta...esolution.html Contrast thresholds data: http://www.clarkvision.com/visastro/omva1/index.html Roger Great resource. Based on that data, I'd conclude that images captured from my microscope might benefit for 65K x 65K resolution, so I'll use 16 bit D/A's to drive my scanning coils. Of course that kind or resolution can only be rendered in print. And represents an 8GB file size. And will take 2 hours to collect.... but might as well build it in. The figure of 10,000:1 dynamic range in any "one view" corresponds to about 12 bits. That's pretty much exactly the nominal dynamic range I've heard quoted for the front end of an SEM. But it might seems no current reproduction technology acheives quite that. -Jeff Ooops, 10K:1 is more like 13.5 bits. But I'm finding a wide range of figures online for dynamic range of the human eye. I visited Barco's website in hopes of finding contrast figures for CRTs and in a white paper comparing CRT and LCD displays, I think they tossed out a figure of 100:1 for the human eye. 1,000 to one has been mentioned here as well. The site referenced above so far holds the title for claiming the widest range. The white paper also tossed out a contrast figure for CRT's of 3,000 to one, about 11.5 bits. The human eye figure of 100:1 is the most surprising. The low contrast of film is also surprising. I guess it (re film) shouldn't be, I know that MgO is the most reflective substance as far as diffuse reflectors go. I forget the figure. -Jeff Do you mean the contrast ratio of film or of photographic paper? Photographic paper, especially colour paper, is quite limited. The contrast ratio of film can be phenomenal, depending on its type. Slow black and white film reversal processed into slides can have extreme contrast, and usually has to be bleached down to the point where it looks reasonable to our eyes. When considering the contrast ratio of the eye, remember this is an instantaneous figure. Our pupils are constantly adapting as we scan around a scene, and the overall constrast we perceive after flitting our eyes around a scene can be far higher. Regards, Steve |
#28
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Steve Underwood wrote:
... Do you mean the contrast ratio of film or of photographic paper? Photographic paper, especially colour paper, is quite limited. The contrast ratio of film can be phenomenal, depending on its type. Slow black and white film reversal processed into slides can have extreme contrast, and usually has to be bleached down to the point where it looks reasonable to our eyes. When considering the contrast ratio of the eye, remember this is an instantaneous figure. Our pupils are constantly adapting as we scan around a scene, and the overall constrast we perceive after flitting our eyes around a scene can be far higher. I understood that the accommodation to light levels provided by pupil size is a rapid but small part of the overall range, and that most of it is provided by light's bleaching of the photoreceptors. Was I wrong? Jerry -- Engineering is the art of making what you want from things you can get. ŻŻŻŻŻŻŻŻŻŻŻŻŻŻŻŻŻŻŻŻŻŻŻŻŻŻŻŻŻŻŻŻŻŻŻŻŻŻŻŻŻŻŻŻŻŻŻŻŻŻ ŻŻŻŻŻŻŻŻŻŻŻŻŻŻŻŻŻŻŻŻŻ |
#29
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Nicholas O. Lindan wrote:
"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. Carbon lamp black is probably the darkest diffuse reflector. It's reflectance in the visual range is about 1.6%: http://pubs.usgs.gov/of/2003/ofr-03-395/ofr-03-395.html specifically: http://pubs.usgs.gov/of/2003/ofr-03-...gds68.1533.gif Spectralon is the brightest: "Spectralon reflectance material gives the highest diffuse reflectance of any known material or coating over the UV-VIS-NIR region of the spectrum." It is 99% in the visual range. http://www.labsphere.com/products.as...=187&catId=188 Roger |
#30
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In article , Roger N. Clark (change username to
rnclark) wrote: 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. Carbon lamp black is probably the darkest diffuse reflector. It's reflectance in the visual range is about 1.6%: The BBC's Test Chart No 57 included (includes?), for the purpose of setting the flare-correction circuitry, a "superblack" rectangle that is actually a box a few inches deep, lined with black velvet. A small rectangular aperture at the front opens onto the surface of the test chart. Any light striking this rectangle enters the dark box and has to undergo several successive reflections by the black velvet before emerging, thus giving the rectangular opening an effective reflectance much lower than would be achievable by any actual surface. Any value of the output signal above dark current level corresponding to this part of the chart is deemed not to have come from the chart at all but from light scattered in the lens, and the circuitry is adjusted accordingly. Rod. |
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