The Sleeping Giant's Sea Lion

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I am using my S95 to take photographs of LCD computer screens which are used to display Microfilm images related to my research. Unfortunately they aren't running a normal OS, so it's not an option to take screen-shots. So far, it's working decently well, though I am running into an issue where the computer screen is reflecting a good amount of glare from the library's lighting wherever there is a black space on the screen. I've tried to reduce glare in two ways:

  1. Adjusting the camera's angle against the screen, and using a smaller aperture to increase depth of field so that more of the image is in focus even though the top and bottom are different distances from the lens.

  2. Adjusting the aspect ratio so that the camera's photo is the same shape as the page I am photographing, to reduce the black space on the computer screen.

However, I'd like to be able to further reduce glare issues. Outside of changing the library's lighting (which I can't do), is there anything that you would suggest that I do with the camera settings?

Below is an example of one of my early shots when I was trying it out that demonstrates the glare. Thanks in advance.

Example image

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3 Answers 3

Polarizers and LCDs may not be the best idea; LCD displays work by polarizing light†, so knocking back the glare may not even be possible without blocking the image altogether, depending on the screen's direction of polarization and the direction of the glare source.

A hood (suggested in Greg's answer) will be your best bet -- but you can use a box rather than fabric or spend ten bucks putting together a frame out of PVC pipe or a bit of wood molding. It should only take a few seconds to set up (and should be relatively easy to explain to librarians as well). That eliminates the extra person.

As for keystoning, taking the time to set the camera up parallel to the screen is your best option. That will also solve your depth-of-field problem.


† The backlight is initially polarized in one direction by a full-screen polarizing filter. Black pixels are black because the liquid crystal is aligned to allow polarized light through at 90 degrees to the backlight polarizer. The liquid crystal in non-black pixels (or, rather, non-black pixel segments) are electrically aligned at some angle other than 90 degrees. There are a number of strategies for aligning the polarization of the pixel segments relative to the full-screen polarizer; they are out of scope here.

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It probably will take another person to help, or you might get creative with gaffer's tape.

Drape a black sheet of cloth over the top and sides of the monitor so no ambient light can directly hit the screen.

Fire away with a helper holding up the cloth so you can shoot under it. Creative use of gaffer's tape (it's like masking tape but leaves no residue) might allow you to do without the helper.

Another thing that will help reduce glare is to add a polarizing filter if you have one. The downside of that is polarizing filters cost you between one and two stops of light, so you might have to increase your ISO speed, use a tripod, or increase the monitor's brightness.

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+1 Just what I was thinking. However, I believe (have not tried, though) that fabric of any color will do fine, not necessarily black. If the adhesion is for a short term, then any clear tape will be fine. –  ysap Feb 6 '11 at 5:42
    
Thanks for the suggestion. I doubt I'll be able to set up a whole setup in a library. I definitely don't have a second person to help me. Are there any good polarizers for the s95 that don't require me to add something permanently? I know about the lensmate setup, but I'd like to have one that I can clip on and use when I want to, but leave off most of the time when I am just using it as a "regular P&S." –  Jason Feb 6 '11 at 6:01
2  
I decided to test the polarizer idea. Have a bare lightbulb just behind my back that when lit, casts a terrible glare on my laptop's LCD (and this is a non-reflective monitor on a Dell Latitude laptop). I took my Canon Circular Polarizer and looked through it. To my surprise, while rotating the ring, there was the expected darkening of the display, but almost no filtering of the light glare! Thus I am not so sure this is a valid solution to the problem. I know CPL filters work great on sunlight reflected from outdoor surfaces, but apparently not so good for artificial light sources on LCD's. –  ysap Feb 6 '11 at 6:51
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I would expect that. The black sections of the screen are not illuminated by the pixels in the monitor, so they are most likely to show reflections from the monitor's surface glass. White should show very little reflection because it's fully illuminated by the pixels behind the glass. You're confusing reflected light with projected light. The black cloth is entirely different than the monitor. –  Greg Feb 6 '11 at 7:16
2  
@ysap - if the bulb is directly behind you rather than hitting the screen obliquely, the reflection won't be polarized. There is another explanation for the rest of what you are seeing; I'm including that in my answer. –  user2719 Feb 6 '11 at 10:53

If the light is directly behind you, then wear a black shirt and stand between the light and the screen. If the light is overhead, you can prop something black over top of the screen. A piece of cardboard may do, or you may be able to use a collapsible circular reflector that has a black side. They even make the same thing for car windshields, so you may find it cheaper/faster from an auto store.

One thing to keep in mind, if that reflection is always on the same side of the monitor, no matter where you hold the camera, then it's possible it's the backlight of the LCD shining through. If that's the case, no amount of shielding will help, and you'll just have to under expose the image a little and then correct it in a photo editor as best you can.

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