Any experience with short throw projectors?

[SHCP]

Hey all,
Our school just purchased a Hitachi CP-AX3505. It's ideal distance from the screen is 15" to 25", and at that distance it projects an amazing 10-14' wide image. The problem is that the top of the image is very blurry, while the bottom is quite clear. I have tried focusing, adjusting the keystone and tilting the projector, but nothing makes the image focused top to bottom. Any thoughts?
Tim

 

[MNicolai]

That projector isn't meant to be that far from the screen. The literature I've seen shows 60"-100" diagonal images being optimal, not 10'-14' wide images.

3600lm is a very small projector even for a conference room where people are close to the screen. In a theatre environment on a larger screen, you're asking your projector for something it was not designed for. In terms of brightness, this may be sufficient for you if you run it in a dimly lit room, but it comes at the cost of not being able to focus evenly top to bottom because the optics aren't designed to scale to larger image sizes.

Pushing a typical projector beyond its usual screen size will give you a darker image. The physics of a short throw are fundamentally different. The optics aren't designed to scale to larger image sizes without the kinds of problems you're seeing.

On top of that, generally low-brightness short throws are made as cheap classroom projectors. For that environment they're usually fine — the cost-savings is worth the image not being optically superior, but in a theatre environment that can be problematic.

As a general rule, anything less than 5000lm is limited in features and optical quality. Above 5000lm and you start to get more options, interchangeable lenses, lens shift (instead of keystone correction — huuuugggee difference), etc. Anything sub 5000lm is usually a race-to-the-bottom in terms of quality.


Sent from my iPhone using Tapatalk

 

[microstar]

Are you placing the projector above or below the image/screen? If you look at the manual, it should tell you how many inches above the top of the image or below the bottom of the image to place the projector, which might need some experimentation given the throws and image widths you are using. Also Mike's points above.

 

[Footer]

Those short throw projectors do some really weird lens stuff to keep the pixels the farthest from the projector the same size at the ones closer to the projector. If you are outside of its operating range you won't get a good image, you will be beyond what the lens can focus to. This thing is designed to be set on the end of a board room table and hit a whiteboard 2' away. It is not meant to throw a 10' wide or more image.

 

[coldnorth57]

http://www.projectorcentral.com/Hitachi-CP-AX3505-projection-calculator-pro.htm

you need to look at this page

 

[ruinexplorer]

Your best bet will be to focus the center of the image and have the top and bottom out of focus. Alter your content so that focus isn't critical.