Anyone recommend a good Projector?

[Rob Reynolds]

The MX 631 ST projector is out of production. Has anyone found a replacement? Must be short throw and 4:3 aspect. Thanks

[ryanwildevans]

Amazon still has them (17 left as of 12/12/16) if you needed one soon.

[Rob Reynolds]

I don’t believe that model does 4:3, which I think is important to match the camera. Can anyone comment on that?

[ryanwildevans]

I just went and double checked, that is the exact model I have: BenQ MW632ST 3,000 Lumens
It does in fact have a 4:3

[Oliver Kreylos]

The BenQ MW632ST’s native resolution is 1280×800, which yields a 16:10 aspect ratio. If you feed it a 4:3 1024×768 video signal, it might do the right thing and pad the signal on all sides so that you get a 4:3 inset of the native display panel. With DLP’s high contrast, you might not notice the overprojection.

When feeding a projector a non-native signal, look through all the menu options to see if there is some way to force its display engine to use 1:1 pixel mapping. By default, most projectors scale incoming video signals to their native resolutions, which introduces ugly artifacts, and might even stretch the image in one direction.

The same caveat goes for in-projector keystone correction: don’t use it unless you absolutely have to. You don’t need it for the AR Sandbox, as the projector calibration procedure takes care of keystone distortion automatically.

[Anonymous]

I just went and double checked, that is the exact model I have: BenQ MW632ST 3,000 Lumens
It does in fact have a 4:3

That model seems to have an even shorter throw than the originally recommended MX631ST projector, which seems to imply it would have to be mounted closer to the surface of the sand. What is the height of both your sand surface from the floor and the projector from the sand? Also, is that an “above-axis” projection model like the MX631ST – i.e. must it be mounted at the edge of the sandbox?

[Anonymous]

The BenQ MW632ST’s native resolution is 1280×800, which yields a 16:10 aspect ratio. If you feed it a 4:3 1024×768 video signal, it might do the right thing and pad the signal on all sides so that you get a 4:3 inset of the native display panel. With DLP’s high contrast, you might not notice the overprojection.

Oliver, would building a sandbox in a 16:10 aspect ratio instead of 4:3 work, or does the software assume a 4:3 aspect ratio for both projector and sensor? Mounting the sensor at a height which covers the longer dimension would “waste” some sensor resolution on either side of the shorter dimension, but aside from the wasted sensor area, would this pose any problem?

In other words, instead of exactly matching aspect ratios for the sensor and projector, would it be possible to “fit” the projection within the sensor area?

-Steve

[Anonymous]

The MX 631 ST projector is out of production. Has anyone found a replacement? Must be short throw and 4:3 aspect. Thanks

I’m currently assisting another science center with an AR Sandbox installation and came across the following projector which looks quite promising…

Optoma W345

It has a 1.2 throw ratio, which means it must either be mounted a bit higher or a mirror must be used. Being 8-10 inches higher would not necessarily be a bad thing IMO. It also has slightly higher lumens, a better contrast ratio, and is a bit cheaper than the BenQ MW632ST. Anyone have firsthand experience with the Optoma W345 projector?

And oh yeah, it also has a 3-year warranty. I can’t find much in the way of reviews, but perhaps that’s because it was released rather recently. Other models of the Optoma brand do seem to get good reviews though.

-Steve

[Oliver Kreylos]

The AR Sandbox can run at any aspect ratio, but I would recommend running it at 4:3 because the Kinect’s resolution is already a limiting factor. I think it’s better to throw away some display pixels by overprojecting than to reduce resolution even further by overscanning.

The Optoma projector requires a projection distance of 57″ +-5% to fill a 40″x30″ sandbox, which is approx. 17″ more than the old BenQ (and the Kinect). Apart from that, it should do a fine job.

[Anonymous]

Thanks for the info, Oliver. I’m a bit puzzled by the following though…

The Optoma projector requires a projection distance of 57″ +-5% to fill a 40″x30″ sandbox, which is approx. 17″ more than the old BenQ (and the Kinect).

The specs indicate a throw ratio of “1.18 – 1.54”. I assume that means it’s adjustable. If set to the low end of that range, wouldn’t that be just 48 inches above the sand?

Thanks for the clarification.

EDIT: Oh wait, is it because of the difference in aspect ratio between the projector and sandbox – i.e. the projector has to be farther to fill the smaller sandbox dimension?

-Steve

[Oliver Kreylos]

To fill a 40″x30″ sandbox, you have to overproject to a size of 48″x30″ due to the projector’s 16:10 aspect ratio. At maximum zoom, that yields a distance of 48″ * 1.18 = 56.64″. There’s a projection calculator available from the product page you linked where you can try different projection sizes.

[Anonymous]

Ok, yeah I think I got it now. Thanks much!

[Anonymous]

That model seems to have an even shorter throw than the originally recommended MX631ST projector, which seems to imply it would have to be mounted closer to the surface of the sand.

Actually, I was neglecting the BenQ MW632ST’s 16:10 aspect ratio, which means it would need to be a bit further (3-4 inches) from the sand surface (assuming my calculation is correct) than the originally recommended BenQ MX631ST. So basically, it would need to be about 43″ above the sand instead of 40″. It doesn’t seem like that would pose much of a design problem.

-Steve

[Frank Conforti]

We have ours set up using a Benq MW632ST and have no issues with it. It is mounted more or less at the same height as the Kinect and projects 1024×768 perfectly. I asked our IT dept to get one “closest to the MX631ST” and we got this one. Bumble bee principle in action.

I’m now building one for home use (my hi-tech zen garden as it were) so I’m on the hunt for something less expensive. I’m very interested in seeing what others have successfully used that’s less than $500 as it is coming out of my pocket this time!

[Anonymous]

Dear Sir ;

I would like to get big size sandbox aprx 75 cm x 250 cm . Is it possible with one kineckt ?

I tried but I just get good result only middle of the box .

Waiting your reply.

[Author]

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