Is there a device to compensate for no vertical lens shift?

phil2415

Standard Member
I have an Epson EH-TW6100 projector and, sadly, am not in a position financially to replace it at the moment. I've also just moved house (the two things are not unrelated!). The previous owners of the house had set up a small snug in the eaves of the roof as a little cinema room and it's quite a nice space so I wouldn't mind using it for the same thing myself. The main problem is that the recessed space in the wall they've created for the projector is way higher than where the top of the screen will be.

I was wondering whether it'd be possible to create some kind of periscope-like device which would attach to the projector's lens and, using two mirrors at 45° angles, direct the light from the projector to a point lower on the screen wall with minimal loss of picture quality. Something like this:
Periscope.png

Having had the idea, I don't know that I'd have the skills to build one, and the quality and positioning of the mirrors would be critical to the picture quality being maintained, so I looked online to see if anyone sold such a device, but I can't find anything. The search is muddied by the existence of a "Periscope" branded projector.

Does anyone know if this approach would be feasible (even if only theoretically) and whether there's such a product available to buy anywhere?
 

jfinnie

Distinguished Member
Thes kind of things do exist, but in all likelihood will run you to more than a projector with a decent lens shift will. The mirrors used need to be pretty big, because as the image gets further away from where it exits the projector lens it is getting bigger and bigger...

Some commercial examples here:

If you wanted to try and DIY, the things you need are called "first surface mirrors". These delicate mirrors have the mirror surface attached to the top of the glass instead of the bottom of it, which prevents ghost images.

 

ask4me2

Active Member
For a minimal loss of picture quality, you need to get some rather expensive front surface reflecting mirrors, to do this correctly.
tmf-17.gif
And because of the different distances to the projector lens, the projected picture you want to reflect 90 degrees, of the second mirror needs to be larger depending on the distance and zoom setting used.

You can also get away with the use of only one mirror if the projector can survive to be tilted down and projecting away from the screen, and reflected with the correct angle and height toward the screen, something like this

1627733065659.png


the problem using front surface mirrors is that the large ones are expensive, and i wold not like to have them exposed in a small dark home-cinema room.

Guess upgrading to a better projector with the right amount of vertical lens shift needed will be a safer and better solution all together.
 

3rdignis

Active Member
Bolt the projector under a shelf.
 

phil2415

Standard Member
Thanks for the detailed replies, @jfinnie and @ask4me2, they were very interesting! I guess I'm going to be best saving my pennies to get a new projector with VLS at some point (although I don't know if there's a consumer model in production with sufficient VLS for my requirements), and until then, as @3rdignis suggests, put up a shelf!
 

The latest video from AVForums

AVForums Movies Podcast: We review Dune and ask which is the best decade for horror movies?
Subscribe to our YouTube channel
Support AVForums with Patreon

Top Bottom