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DLP Projector Focal Length

post #1 of 6
6/19/03 at 2:23pm
Thread Starter 
I am considering a Sony VLPHS10 DLP Projector. This unit should be avialable soon in the US. Does anyone know how to calculate the focal length? IOW, if I know where I want to mount the projector and how far away the screen will be, how do I calculate the screen size? Conversely, if I know the screen size and where I want to mount it, how do I calculate how far away the projector must be mounted?

Or, do these DLP projectors have variable focal lenghts? If so, is there an "optimal" focal length?

Thank you for your help.

Craig J.
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post #2 of 6
6/20/03 at 12:54am
Moved to Display Devices. Are you sure abut that model#?
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post #3 of 6
6/20/03 at 4:28am
The Sony is an LCD projector not DLP and the HS-10 has been available in the US for some time. If you are referring to throw distance (distance from screen surface to lens in relation to image size) you need to dig up a manual or throw calculator for the unit. Try a search over at the AVS.

Randy
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post #4 of 6
6/20/03 at 1:12pm
Randy is right. This ratio (which has an adjustable range) is different for each projector. Most projectors can vary between around 1.3 and 2 times the screen width from the screen, but you need to check the "throw distance" of that PJ to make sure.

Generally, you want the projector to be as far back as possible within it's throw range as this reduces hotspotting.

NEVER bolt the bracket to the ceiling (or fix the screen to where it can't be moved) until you have both projector and screen. You will most likely need to be able to wiggle *one* of those things to adjust everything in during an install.

-dave

-dave
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post #5 of 6
6/22/03 at 7:43am
Thread Starter 
Thanks fella's! I found my answer at projectorcentral.com. They have a calculator which can determine the appropriate throw distance.

It appears that the VPL-HS10 LCD projector will work perfectly in my HT space with a screen size of about 100 inches -- exactly what I was hoping for.

Dave, your advice about waiting until I have both projector and screen is well taken. I'll let you know how the system works out.

Thanks again,

Craig
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post #6 of 6
2/7/10 at 7:59pm
So what do you do if you want to compare the focal lengths of projector lenses to photographic lenses? The reason why I'm asking is because, I'm one of those strange people who experiment with lenses of all types to find their suitability for photographic purposes. Now if none of you are photographers, you're likely not going to understand that. But if there is a way to calculate the real focal length of any projector lens, as measured from the back of the lens to the image plane, I would like to know.

Xavian-Anderson Macpherson
ShingoshiDao
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