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Old 02-10-2005, 05:14 PM
Menneisyys
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Join Date: Jun 2007
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Quote:
Originally Posted by scoobie
Hi Ultima,

Thanks. I tried taking snapshots of TV (CRT) images with a simple digital web cam that has a camera function and the results were surprisingly good and clear. Out of 10 pics, only 1 has slight 'black band'.

fyi.
Web cams generally use low shutter speed (1/5... 1/15) because they aren't supported to deliver more than 5-10 frames in a second. This is why the 'dark' band is not as visible on webcamera shots as with other, snappier, better cameras. (And, inevitably, webcams deliver much worse image quality than ANY standalone digicam.)

I've made some screenshots with my HP R707 ultra-compact digital camera (in auto mode without tripod) with my 100 Hz Philips and 50 Hz Orion TV sets. The results are as follows:

100 Hz TV sets can always be photographed without problems in any (automatic) mode. That is, you don't need to define long shutter speeds to shoot 100 Hz screens. An example with, for example, a (very fast) shutter speed of 1/124 sec:



(Exp. time 1/124, FNumber: 2.8, ISO Speed 182)

50 Hz TV sets, on the other hand, will have dark bands if you shoot them with 1/(15+) sec shutter speeds. The second image shows less of this effect, so you may have luck at taking screenshots of them.



(Exp. time 1/71, FNumber: 2.8, ISO Speed 200)



(Exp. time 1/41, FNumber: 2.8, ISO Speed 200)

That is, if your camera supports it, try to use shutter speed priority and an 1/2 ... 1/15 shutter speed. If there's no shutter speed priority mode (as with most point-and-shoot cameras), but the ISO is selectable, try using the lowest ISO possible to turn down the shutter speed. Also, if there's aperture priority mode, choose it and use a high aperture - say, 8 or, if it exists, 11 or even 16, to turn up the exposition time. And, of course, use a tripod
 
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