View Full Version : projection setup with a mirror

01-15-2011, 12:18 PM
Hi all,

I have tried rear projection as I have a lot of space behind the screen, but though the image is good quality, I think the image projected from the front is much sharper.

I have read about projecting with mirrors, but not sure how to set it up.
My projector is a short throw Optoma Gametime 700.

1. What size mirror to use
2. How do I calculate throw angle, distance, etc.
3. How do I calculate the curve, if I need to.



01-16-2011, 01:49 PM
Hi Tufeeq,

for basic calculations on a rectangular and flat screen I would start with the calulation tool of projectorcentral:
http://www.projectorcentral.com (http://www.projectorcentral.com/Optoma-GameTime_GT700-projection-calculator-pro.htm&;remove_compare_list=5607)
If you want to use a flat mirror to increase the size of the picture on the screen, you just have to add the distances between projector->mirror and mirror->screen.

For the dimension of a curved screen, you can calulate the horizontal and vertical angle of your flat-screen projection and base your advanced calculations on that. Keep in mind that you need to "warp" your image, if the screen is curved. The central area of a curved sceen is further away from the projection, so the image increases in size there. You can use a parabolic/spherical mirror doing that or use a software like nthusim.

On what kind of screen do you project at the moment? When it is a kind of fabric, the "unsharpness" can come from the uneven structure. I used a shower curtain out of plastic from ikea whith good results. Another possibility is to span special projection screen on a wooden frame. In Germany there is a company called "Gerriets" (http://www.gerriets.de/en/). They have a product called "opera foil" which is an excellent rear (and front) projection material for a reasonable price.

Kind regards,