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Need help with DIY projector screen measurements

post #1 of 7
1/20/04 at 10:21am
Thread Starter 
Ok, bare with me as I'm alittle confused and probably making this more complicated than it is. When measuring the projectors projected image size for making my own screen, do I go with only what of the actual movie is projected, or do I measure and include the white space I have above and below the image, that is made by the projector. Also, how do you compensate for some movies being in a different widescreen format? Like 2.35:1 vs 1.85:1? Either picture is not wider right, just taller? Basically what I need to know is what size should I make my screen for so I cover all different types of widescreen aspects. Right now it's about 96" and I'm using just a white wall.
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post #2 of 7
1/21/04 at 9:59am
I don't have a front projector.. but I'll try to answer your question.

I think it really depends on your projector... if you have a projector that can display a native 16:9 ratio.. you would probably want to build a 16:9 screen.

If you have a projector that has a native display of 4:3, you may want to build a 4:3 screen as widescreen images would be letterboxed within that square. That is, of course unless you only plan to watch widescreen material on that 4:3 projector. In that case, you could get away with building a 1.85:1 screen and matte out the "black bars".

2.35:1 material would be "letterboxed" slightly in both cases.

What kind of projector do you have?
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post #3 of 7
1/21/04 at 10:22am
I have a feeling that newer projectors are much more flexible in their aspect ratio sizing abilities. I'll offer advice based on the projector I have (CRT). With my projector, the image width will be fixed on all material regardless of aspect ratio, that is, 1.33, 1.78, and 2.35:1 will all be the same width. So to keep the image with the greatest height (1.33:1) from spilling over the top and bottom of the screen, I'd match the screen to the aspect ratio with the greatest height. You could then make yourself a masking system to improve the image's contrast.
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post #4 of 7
1/21/04 at 9:38pm
Thread Starter 
Ok, that made things more clear. I have a Panasonic PT-L200u, which is native 16:9 ratio. So I guess I'd measure corner to corner of a 1.33:1 aspect ratio movie and that be the diagonal size of the screen I'd need to build?
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post #5 of 7
1/22/04 at 4:33am
Dave,

I'm not sure I understand what you mean by a native 16:9 (1.78:1). Before you make your screen, project both a 16:9 and 4:3 (1.33:1) onto your wall without adjusting anything in your projector. I am guessing that since it is a native 16:9 projector, any 4:3 image will be shortened to match the 16:9 height. That would mean making the screen a 16:9 rather than a 4:3. So check first to see if that is what will happen.
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post #6 of 7
1/24/04 at 8:00am
Okay, I don't have a projector either, but I do have a RPTV that is 16:9 native. What you essentially have in a FP setup. When I display a 4:3 image, I get black bars on either side of my image. Your FP is LCD (just like my RPTV) and the black isn't "truely black" in appearance. This distracts a lot of folks when watching a movie on a FP setup. I have seen where other people have made "masking" devices to pull over those parts of the screen not be used by what they are watching.

In an effort to mask the left and right sides of the screen, it would be a pretty easy task. In an effort to mask the tops and bottom, it might be more difficult. You might try searching for masking, and also look over at www.avsforum.com in their screen area and projector area to see what types of ideas you can come up with based on other people's efforts.
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post #7 of 7
1/24/04 at 5:53pm
Hello daveD, if you're projector is 16:9 native, then you need to make a 16:9 screen. i'd also add around 2" of black felt around the whole screen, so make your frame 4" longer each way. if you want bigger or smaller mask, adjust measurements accordingly. as for masking, some movies will leave an inch of black on top nd bottom, some will leave 2 inches on top and on bottom. what i plan to do is have felt flaps which extend to 2.40:1, with metal strips running underneath the felt on the sides, and strong neodymium magnets in the sides of the flaps. when it's time to watch star wars, just go over and pull the flaps down to 2.40:1, for 1.85:1, just pull the flap down only far enough to cover the blank spot. it all sounds really easy in my head.

eric
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