Short-Throw Projectors

[FredK]

Would appreciate any recommendations and comments regarding short-throw projectors.

I'm planning a 3 projector visual project utilizing a curved screen and Sol7. Space constraints essentially limit me to use of short-throws. I realize there is already some sketchy info here but am curious if anyone has anything new to add.

Thanks,

FredK

[BHawthorne]

The Optoma EX525ST is readily available and works great for me. I know a few others are using that model too here. Go with DLP projector and look for 0.6:1 lens throw.

[dcutugno]

I'm going to use 3 Sanyo DWL 100 ,ST projectors widescreen 1280x800 each more fov and resolution.
I'm wayting to source them.

They cost a little more than the 525st...

[FredK]

Thanks for responding.....

The better resolution for the WXGAs (Sanyo) is intriguing. However, the way I see it is that the wider display format is more of a negative particularly in limited projection space requiring short-throws....that is, there is less vertical space "fill" than what the 4:3 aspect ratio XGAs would offer. Such I think is important for flight simming - sightseeing at high altitude, landings, etc. My thought is to go with WXGA but then run it in emulated 4:3 aspect ratio to capture the best of both worlds. I'm not sure how that actually would work regarding any issues with display quality, performance etc.

FredK

[BHawthorne]

Re: The 5:4 vs 16:9 issue...

16:9 is going to have some technical issues with the curvature of the screen. The wider you get with the projector aspect ratio per projector the more distortion and focus issues you get. You're goign to lose a lot of empty pixels off the top and bottom center of your projections with 16:9 with how projection geometry works out on a circular screen. It's really hard to explain what I mean by "lost pixels" without understanding how projecting onto a circular screen works. The projection bows in the center because of the circular arc of the screen. In use of 16:9 the bow is really pronounced, enough that you might lose about 20% of your pixel capability outside the regular pre-warp final picture area. I really suggest 5:4 vs 16:9. I got rid of my 16:9 because of the issues I mention. There are more disadvantage to 16:9 than advantage when it comes to circular screen projection. It goes against logic, but how the mechanics work out it's better with 5:4.

[IanH1960]

Brian,

Can you give a quick indication of the radius of your curved screen? Any thoughts as to how small it might be possible to go..

Also, do you use Sol7?

....thinking ahead to a new project.

Ian

[BHawthorne]

Brian,

Can you give a quick indication of the radius of your curved screen? Any thoughts as to how small it might be possible to go..

Also, do you use Sol7?

....thinking ahead to a new project.

Ian

I prefer to go by the name of Brad, but I've been called a lot worse I suppose.

Where you pick up or lose aspect ratio is not in your projector but rather how tight your screen curvature is. You can go a lot wider FOV with a screen constrained within a 10x10 foot room than a screen constrained in a 15x15 foot room. The destortion I mentioned in my last post is also more pronounced the smaller the area is for the screen. I wouldn't go any smaller than 10x10 foot because you begin to lose excessive amounts of "empty pixel" area. Don't think of projectors in terms of flat projection aspect ratio but rather what you can project into within the circular arc of a screen area within the capabilities of the lens throw. All circular projection will have "empty pixels", it's just that it's up to you how you end up doing your setup based on the curvature size and whatever height you end up using for the projection. The taller the projection and the smaller the room the more FOV you cover, but also the more pixels you lose in resolution. You need to find a good balance. For me it's a 13x13 foot room. I didn't mathematicly come up with 13x13 foot, it's just the room size I had available.

Keep in mind that the bow distortion I mention is largely irrelevant to the projection once using Sol7. It's just that you are losing sharpness in your projection because of the usable resolution left within the pre-warp area if you get too extreme with the FOV per projector.

[IanH1960]

Apologies Brad - don't know where I got Brian from!

Thanks for the information...

Ian

[FredK]

Brad -

Your 13 X 13 recommendation is reassuring! By dumb luck that is almost exactly the space I'm dealing with!

Did you ever try to run your 16:9 in 4:3? I would assume such would result in even greater loss of pixels because of the unused "dark space" (left and right) although I'm not really sure how the emulation works in that regard.

Thanks for providing your info - very helpful - anything else I need to know?

FredK

[BHawthorne]

To clarify what I mean about lost pixels, here is an uncorrected projection vs. a pre-warped Sol7 projection. Same exact perspective of camera. The "humps" are essentially "lost pixels".

Uncorrected:


Pre-Warped with Sol7: