Projector Calculator help reduce digital keystone? - AVS Forum
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post #1 of 7 Old 05-18-2012, 01:29 PM - Thread Starter
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I'm leaning heavily towards the Optoma HD33 and a 135 inch screen for my 100% light controlled theater room. So I'm having trouble understanding the following calculator:

http://www.projectorcentral.com/Opto...ulator-pro.htm

People have scared me away from digital keystoning, so I would like to use it as minimally as possible. So according to the calc, I must be between 14'9" and 17'8". Does that mean any distance between those I will absolutely not have to use digital keystone? It will produce a perfect rectangle image? What I don't understand is when I change the gain, the recommended throw distance also changes, how does digital keystone/perfect rectangular image come into play?
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post #2 of 7 Old 05-18-2012, 03:19 PM
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Keystoning has NOTHING to do with distance. It used when the projector is not mounted vertically and horizontally where the manufacturer says.

If the projector is mounted too high or too low, and it has to be tilted to get the image on the screen, then the image is not square and keystoning is used to correct the geometry.

Same with horizontal positioning. Except horizontal is easier. The projector is mounted SQUARE to the screen and the lens is in perfect alignment with the vertical center of the screen.

Bottom line, if you mount the projector exactly according the manual, then you should have NO reason to use keystoning.
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post #3 of 7 Old 05-18-2012, 03:28 PM
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I'm not familiar with the Optoma, but keystone is normally needed if the pj is placed outside the range of the lens shift, maximum ranges. If your pj is placed within those ranges, in relation to where the screen is, you shouldn't need to use the keystone feature.

It looks like the 14'9 is referring to the distance from the screen, and as you change the gain, it will change the optimal distance from the screen, due to brightness either lowering, or increasing.

This isn't necessarily related to the use of keystone, unless your placing the projector at say, 15' away from the screen, but also 10' ABOVE it, which would be way outside of the capabilities/range of the lens shift feature. That is an extreme example, but might get the point across I think?
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post #4 of 7 Old 05-18-2012, 04:00 PM
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I don't believe that a projector has both lens shift AND keystone. If someone knows of one that does, please chime in. But all the projectors I've seen have one or the other.
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post #5 of 7 Old 05-18-2012, 06:14 PM - Thread Starter
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awesome!! thanks guys, this is my first pj purchase and want to make sure I'm doing it right. answered a lot of Q's and eased my mind quite a bit.
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post #6 of 7 Old 05-19-2012, 02:00 AM
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Quote:
Originally Posted by Sheridan1952 View Post

I don't believe that a projector has both lens shift AND keystone. If someone knows of one that does, please chime in. But all the projectors I've seen have one or the other.

The new Epson 5010/6010 do, and there are others.
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post #7 of 7 Old 05-19-2012, 06:02 AM
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Thanks, I'll check them out.
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