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In article ,
wrote: Kibo informs me that Hugh Nagle stated that: Now, I know I could do a screen capture, but I was wondering if anyone had any ideas on how best to photograph a computer screen. It's easy. You'll need a tripod, positioned with the camera as parallel as possible with the screen, & a shutter speed that's an *exact* multiple of the displays refresh rate to prevent dark bars appearing in the photo. Eg: to photograph an American TV screen (60Hz field rate, 30Hz refresh rate), you'd use a shutter speed of 1/30th, 1/15th, etc. Not to diminish the fine photography advice here, but there's gotta be a way on a MAC to grab the screen and save it to a file in some graphics format. I don't do MAC. In a windoze system I can save the entire screen, or just the active panel to a BMP file, and then do anything I want with it. -- Al Dykes ----------- adykes at p a n i x . c o m |
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In article ,
wrote: Kibo informs me that Hugh Nagle stated that: Now, I know I could do a screen capture, but I was wondering if anyone had any ideas on how best to photograph a computer screen. It's easy. You'll need a tripod, positioned with the camera as parallel as possible with the screen, & a shutter speed that's an *exact* multiple of the displays refresh rate to prevent dark bars appearing in the photo. Eg: to photograph an American TV screen (60Hz field rate, 30Hz refresh rate), you'd use a shutter speed of 1/30th, 1/15th, etc. Not to diminish the fine photography advice here, but there's gotta be a way on a MAC to grab the screen and save it to a file in some graphics format. I don't do MAC. In a windoze system I can save the entire screen, or just the active panel to a BMP file, and then do anything I want with it. -- Al Dykes ----------- adykes at p a n i x . c o m |
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Big Bill writes:
I've taken many screen shots with my C3030; no problems at 1/60 or 1/30 sec. I also did this with my older Konica FT-1 Motor. I've never heard that mechanical shutters aren't good enough for this before. Where did you get this info? Personal experience. Now, if you're shooting with a P&S or rangefinder camera with an in-lens shutter, the shutter actually opens gradually and closes gradually over the space of several milliseconds, and it is in a position where it controls light over the whole frame area at once. At speeds higher than 1/60, less than the whole screen will be illuminated (as you'd expect) and the illuminated area will have a soft edge where brightness increases or decreases over several scan lines. When you shoot at 1/30, this means that any overlap or lack of overlap will have a soft edge, making it less visible. But a focal-plane shutter passes or blocks light very rapidly. If you shoot a CRT at faster than 1/60, you will see an illuminated band with very crisp edges (it will be diagonal with a horizontal-running shutter, horizontal with a vertical-running shutter). And if you try to expose for exactly 1/30 second, you'll almost certainly see either a dark band because the exposure was really less than 1/60, or a light band where some part of the screen got exposed twice because the exposure was slightly more than 1/60. I've seen this myself in film SLR shots. Photography magazines used to test shutter accuracy. A shutter that was within 1/10 stop was considered very good - but a 1/10 stop exposure error is still a 7% time error. Mechanical shutters just aren't that precise. Dave |
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Big Bill writes:
I've taken many screen shots with my C3030; no problems at 1/60 or 1/30 sec. I also did this with my older Konica FT-1 Motor. I've never heard that mechanical shutters aren't good enough for this before. Where did you get this info? Personal experience. Now, if you're shooting with a P&S or rangefinder camera with an in-lens shutter, the shutter actually opens gradually and closes gradually over the space of several milliseconds, and it is in a position where it controls light over the whole frame area at once. At speeds higher than 1/60, less than the whole screen will be illuminated (as you'd expect) and the illuminated area will have a soft edge where brightness increases or decreases over several scan lines. When you shoot at 1/30, this means that any overlap or lack of overlap will have a soft edge, making it less visible. But a focal-plane shutter passes or blocks light very rapidly. If you shoot a CRT at faster than 1/60, you will see an illuminated band with very crisp edges (it will be diagonal with a horizontal-running shutter, horizontal with a vertical-running shutter). And if you try to expose for exactly 1/30 second, you'll almost certainly see either a dark band because the exposure was really less than 1/60, or a light band where some part of the screen got exposed twice because the exposure was slightly more than 1/60. I've seen this myself in film SLR shots. Photography magazines used to test shutter accuracy. A shutter that was within 1/10 stop was considered very good - but a 1/10 stop exposure error is still a 7% time error. Mechanical shutters just aren't that precise. Dave |
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