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Old Mar 9, 2005, 10:57 AM   #1
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Hi, all.

What's the best way (if any) of avoiding or minimizing the moiré effect in taking pictures of a computer screen?

This is for a one-shot project.

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Old Mar 9, 2005, 11:13 AM   #2
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Shooting any kind of video screen (TV or computer) is a challenge. First of all, make sure your shutter speed is slower than the video refresh rate of the display. With a TV, the screen refreshes 30 times per second so a shutter speed of 1/30th or slower is required. For a computer screen, the refresh rate varies with the video card and monitor. However, 1/30th shutter speed should still work OK if the display is not changing.

The camera should be on a tripod. Adjust the zoom to fill the frame with the video display. The room should be dark to avoid reflections on the video screen.

If you are having trouble with Moire patterns in the final image, you can try using a different image size or jpeg compression in the camera. You might also try varying the distance between the lens and the video display. If you are getting Moire in the LCD display on the camera but not in the final image, don't worry about it. It's not a problem.

One last thing you could try is to change the ISO setting, however, I don't think that will help much.

Good luck.

Cal Rasmussen
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Old Mar 9, 2005, 3:14 PM   #3
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I often use shutter priority on my camera. My computer has a button with which I can go into a menu and find out what the refresh rate is, I then set my shutter speed accordingly like calr said. If necessary I will boost the ISO, but it's not often required unless I'm shooting something that's dark. Also I usually try to fill the frame (or nearly so) with the monitor. Depending on what I want to do with it, I'll use center weighted or occasionally spot metering (but if you fill the frame with the monitor be careful, and if you're not sure, use full-frame metering or center weighted metering.)

I usually shoot at full resolution and minimum compression, and especially if I "crop"/zoom in on a specific window, I see quite severe pixelation. For example (although I won't attach a pic right now) I run a game I usually play (Team Fortress Classic (on Steam) at about 640x480 or 800x600 in a window (not full screen). My camera's resolution is 2048x1536, so I can see pixelation. HOWEVER, I think it is better to set the resolution too high and downsize later, rather than set it too low and upsize later. Anyone with better experience / a Canon EOS-1Ds Mark II / EOS-20D / EOS-1DS, Kodak DCS SLR/whatever, Nikon D100, etc, have differing opinions on this? (btw I use a Canon S1 IS.)
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Old Mar 13, 2005, 2:01 PM   #4
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If you have a manual focus camera, it should not be to much of a problem. Autofocus will often lock in on the shadow mask and this is what give the moire patterns. If using autofocus, move the camera back or forward slightly after locking in the focus. Good luck with you project.

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