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In article <[email protected]>, [email protected] (Kouhia Juhana) |
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writes: |
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>In article <[email protected]> [email protected] (Steve |
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>Hollasch) writes: |
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>> I think you're proposal would work to get an extra one, maybe two extra |
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>>bits of color resolution. However, if you had a display that chould do only |
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>>zero or full intensity for each primary, I don't think you'd get great |
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>>equivalent 24-bit photographs. |
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>I have not suggested to do so; I wrote about problems, and the problem |
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>were clearly visible with 7 bit b&w images; not to mention 24 bit images. |
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[ description of experiment deleted ] |
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>If the 1 bit images are viewed quickly and in sync with screen, |
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>then 100 intensities could be better than we have -- I dunno. |
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[ more deleted ] |
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>In any case, getting black color with slow machines is problem. |
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>I could try it on our 8 bit screens but I don't know how to |
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>render pixels with X in constant time. I recall our double buffer |
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>has other image color and one b&w -- that doesn't help either. |
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>Maybe I should dump photos to screen with low level code; how? |
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A few years ago a friend and I took some 256 grey-level photos from |
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a 1 bit Mac Plus screen using this method. Displaying all 256 levels |
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synchronized to the 60Hz display took about 10 seconds. After |
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experimenting with different aperture settings and screen |
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brightnesses we found a range that worked well, giving respectable |
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contrast. The quality of the images was pretty good. There were no |
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visible contrast bands. |
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To minimize the exposure time the display program built 255 |
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different 1 bit frames. The first contained a dot only for pixels |
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that had value 255, the second only for pixels that had value 254, |
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etc. These frames were stored using a sparse data structure that was |
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very fast to 'or' onto the screen in sequence. Creating these |
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frames sometimes took 5-10 minutes on that old Mac, but the camera |
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shutter was closed during that time anyway. And yes, we wrote |
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directly to the screen memory. Mea culpa. |
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Our biggest problem was that small images were displayed in the |
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top left corner of the screen instead of the center. It took |
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an extra week to have the film developed and printed, because the |
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processors took the trouble to manually move the all images into |
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the center of the print. Who'd have guessed? |
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regards, |
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Jon Rowlands |
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