Widescreen Gaming Forum

I plan on using 2x 1080p projectors with edge blending onto a screen about 2.2m across and have a few questions.

1) It’s very important to me that the centre section is pin sharp and free from fuzzy overlap. Would software (Nthusim, Warpalizer, etc) be able to blend so I can’t tell it’s actually two images from a viewing distance of about 1m?

2) If I overlap say 20% of the image, how would a PC handle this? Would it be 3840x1080 resolution, or the ‘blended’ 3072x1080 resolution?

I would like to mount the projectors higher than the factory throw offset (from say 33% offset to say 45% offset) for a given height. If I increase this height relative to the projected image, I will get some keystone effect which I can correct.

3) Will the image be noticeably brighter at the top of the image? Can I correct this with software?


Thanks in advance.

1) It'll deal with most of the issue, but we're talking about a method in general that requires blending of two separate projectors. Even hitting the power button on the projectors to turn them on and off will effect your calibration by a few pixels. Use your remote to power them on and off and use as rigid as possible projector mounts and mounting location. I'm not going to gloss over the truth and say that you're going to have razor sharp blends all the time. You'll need to dial things back in a minor bit all the time to retain that razor sharpness. That'll take all of 2-3 minutes though.

2) It still retains the unblended resolution, so you'd still be 5760x1080 blended or unblended. If you're watching video content MPC has detailed 10-key independent control over both vertical and horizontal aspect ratio. Dial in things to the proper AR as needed with video content. For game content I really don't find it to be an issue. With a multi-projector blended setup the screen design and size sets the AR, not what resolution you use. Also to clarify, NTHUSIM requires a fixed 15% overlap, so you wouldn't have 10% or 20%. Throw offset of 33 or 40% is irrelevant as long as you have full coverage on the screen. Pre-warp correct as needed. The reason why NTHUSIM exists is to correct everything projected on a grid. It's not merely keystone correcting the corners, it's pre-warping the whole projection content on a custom grid.

3) I've seen no brightness variation between top and bottom of projection regardless of the angle of the projection. The only time you have color brightness issue is when you're projecting true black. You'll still see the area of projector overlap, but but that is at only true black. At 2-3% light levels projected it disappears. Setting black levels in the video settings to something like 4-5% would probably deal with it. I've never had a want to mess with color correction sliders in the control panel though.

_________________
Brad Hawthorne
Product Manager
Nthusim Pty. Ltd. | www.nthusim.com

2) .....For game content I really don't find it to be an issue. With a multi-projector blended setup the screen design and size sets the AR, not what resolution you use.

Thanks Brad, really appreciate the input.

2) So in game, would it be the ‘blended’ 3552x1080 resolution? I have used (1920*0.85)+1920 to get this resolution, allowing for the 15% overlap in the centre.

If I am at about 1m distance, I may be starting to see the pixels. If I can't align them perfectly, would I see this as fuzziness?

[quote]
2) .....For game content I really don't find it to be an issue. With a multi-projector blended setup the screen design and size sets the AR, not what resolution you use.

Thanks Brad, really appreciate the input.

2) So in game, would it be the ‘blended’ 3552x1080 resolution? I have used (1920*0.85)+1920 to get this resolution, allowing for the 15% overlap in the centre.

If I am at about 1m distance, I may be starting to see the pixels. If I can't align them perfectly, would I see this as fuzziness?

In-game you'd set a resolution of 5760x1080. It'll still function as 5760x1080 as far as the computer is concerned, but the aspect ratio of the projection will be 3.28 instead of 3.56. I'm not sure what 1 meter is conversion to feet but a typical viewing distance in a room setup would be 6-10 foot back on the center.line of the screen depending upon the content being viewed. Simulator content typically is viewed closer than movie content, etc...it's situational. I'm also used to 720p not 1080p multi-projection, so it's even more prone to seeing the pixels. You'll be able to dial it in sharp, the question is how often you fine tune it to maintain that sharpness. I nitpick things so if I see any misalignment I always fix it before I use the setup.

The deciding factor on just how pixel-ly and bright your setup will be is your screen design. The sharpest will be at about 48" projection height. It doesn't make any sense to me to go any less projection height than that on a full room circular setup. I'd also go not taller projection than 72". I run a 60" projection height on my particular 720p triple setup. If the pixel size is an important factor shoot for 48" projection height to keep the pixel size small. I'm not used to thinking in meters, so I don't know exactly how well my suggestions relate to what you have in mind for a screen size and viewing distance.

_________________
Brad Hawthorne
Product Manager
Nthusim Pty. Ltd. | www.nthusim.com

The solution is 3 projectors so the middle is always independent :D

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