Newbie screen choice question: aspect ratios, etc - AVS Forum
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post #1 of 2 Old 05-31-2001, 01:42 PM - Thread Starter
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I'm outfitting a 15x20 media room with a ceiling mounted JVC G15 D-ILA projector connected primarily to a HTPC set to drive the projector at its native resolution (1365x1024). This HTPC will be used for DVD playback, regular TV reception, computer screens (games), and HDTV reception, probably in that order of frequency.

The screen will be mounted along the short 15' axis at the far wall to get maximum distance between seating/projector and the screen. Because of sloping ceilings on the sides of the long dimension axis, the maximum case width of the screen is effectively limited to 11 feet or so.

Because there's an alcove behind the screen, I'd like to put the center speaker behind the screen and use some acoustically transparent material. Because this is a D-ILA projector, I'd like to go with the Stewart GrayHawk material. I also want an electrically raisable / lowerable screen, to access the alcove area behind the screen (a closet door is back there).

The only problem now is to choose an actual model from the myriad of models Stewart lists. From reading through the Stewart web site, my naive selection would be a 16:9 Vertical ElectriScreen ElectriMask, probably the EMSN135H or EMSN123H. This would give me 118 or 107 inch width, respectively, at the 16:9 ratio (for HDTV, some widescreen DVD, right?), and let me automatically mask back to 4:3 ratio for TV, computer, or pan&scan DVD.

My questions are:
[list=1][*]Is this a reasonable choice of screen model, given the parameters I've outlined, or am I missing something / looking at the wrong screen models on the web site?[*]For aspect ratios other than 16:9 or 4:3, I guess I just leave the screen with the masks retracted in 16:9 mode, and just don't take up the whole screen, right?[*]For native 1365x1024 resolution from an HTPC, I assume the JVC G15 projects a 4:3 image, right? To fill a 16:9 screen, would the image just use less than the full 1024 scan lines (leaving black above and below) to get the right aspect ratio, and be zoomed larger to fill the screen? Or what is the mechanism that a digital projector uses to project different aspect ratios?[*]I've heard references to a "panamorph" lense; is this a lense to stretch a 4:3 image to 16:9 so the full 1365x1024 resolution of a projector can be used in 16:9 mode? If so, would I manually need to change lenses every time I changed to source materials with different aspect ratios?[*]Is there a FAQ on this stuff so I can stop asking stupid questions (like that would work, right!)?[/list=a]

Thanks for any response!

------------------
- Dan Butterfield

- Dan Butterfield
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post #2 of 2 Old 05-31-2001, 08:53 PM
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1. Your choice of screen seems reasonable, it looks like it's a motorized screen with masking for the side of the screen? I'm not to familiar with the specific models of screens, so hopefully someone else will answer this. With a G15 you definitely want to go with a 16*9 to really make the most of the brightness that it puts out. Unless you have a high ceiling, you couldn't fit a 4:3 screen big enough to do the projector justice. Going 16*9 allows you to have a wider screen with the same ceiling height.

2. Yes, unless you want to go nuts and get 4-way masking on a motorized screen ($$$+). Since you have an HTPC you might be able to shift a 2.35:1 image to the top of the 16:9 screen and roll the screen up a bit to get a proper black border around the 2.35:1 image.

3. Yes the G15 is natively 4:3. You're right about the aspect ratios.

4. That's not exactly what the Panamorph does, it actually compresses the image *vertically* instead of a horizontal expansion. The ISCO anamorphic lens expands horizontally, though. Anyways, an anamorphic lens will allow you to use the full panel resolution with 16*9 material. With the exception of 4:3 material, other aspect ratios are generally letterboxed in a 16*9 image so there would be no need to change lenses thos aspect ratios (2.35:1 for example). 4:3 material can be resampled to take the centre 900*1024 (approx.) pixels in a 16*9, but if you're playing games you probably want to move the lens out of the way. The differences between the ISCO and the Panamorph come into play here. With the ISCO, removing the lens will produce a 4:3 image in the centre of a 16:9 screen. With the Panamorph, removing the lens will produce and image that fills the 16*9 screen and spills over the top and bottom. In your case an ISCO is probably what you want.

5. I don't think there is a screen FAQ here, but there is a D-ILA FAQ in the digital projectors forum.

Regards,

Kam Fung
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