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Has anyone used a periscope system to deal with a low projection opening or low ceiling? Any thoughts? How degraded is the projected image at, say, 80 feet?

Doing it right now. Use first-surface mirrors ($$$). Do not mount ANYTHING to the projectors (vibration). The bottom mirror will only need to be about 12x12. After a rise of about four feet, our upper mirror is abot 22x34. Port glass is huge so expect to pay a lot of the Star Light glass. Make sure all the mirros are adjustable on all three axis. Do all your setting up with the less expensive standard mirrors. You will be breaking them. Don't ask me how I know that... If you use lasar quality mirrors, you will have no image deteriation. I'll post pix when I get this finished.

Vibration and dirty optics will be your most likely issues. Any dust or haze on those front surface mirrors will "kill" contrast, and the surfaces are very delicate and easy to scratch while cleaning. Be sure the mirrors are truly flat and without optical distortion. Figure at least 5-10 percent light loss at each surface.

IMHO, don't do it unless you really have no alternative.

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John P. Pytlak, Senior Technical Specialist
Customer Technical Services
Entertainment Imaging
Research Labs, Building 69, Room 7525A
Eastman Kodak Company
Rochester, NY 14650-1922
Telephone: +1 585-477-5325 Cell: +1 585-781-4036 Fax: +1 585-722-7243
E-Mail: This e-mail address is being protected from spambots. You need JavaScript enabled to view it
Website: http://www.kodak.com/go/motion

Avalon and John, Thanks for the information. Two very different opinions.

Avalon, when you say "laser quality" mirrors, what does that mean regarding cost? Are we talking, like, NASA costs? Where does one purchase these mirrors?

Love to see your pix.

Thanks again

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Some vendors:
http://www.delphiglass.com/index.cfm?page=itemView&itemsysid=130206
http://www.surplusshed.com/pages/item/l3312.html
http://www.ocli.com/pdf_files/products/fsm_proj_ds.pdf
http://www.richmondproducts.com/705FronSurfaceMirrorKit.htm
http://www.abrisa.com/front_surface_mirror.html

You might be able to salvage some large front surface mirrors from some old large rear screen projection television sets.

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John P. Pytlak, Senior Technical Specialist
Customer Technical Services
Entertainment Imaging
Research Labs, Building 69, Room 7525A
Eastman Kodak Company
Rochester, NY 14650-1922
Telephone: +1 585-477-5325 Cell: +1 585-781-4036 Fax: +1 585-722-7243
E-Mail: This e-mail address is being protected from spambots. You need JavaScript enabled to view it
Website: http://www.kodak.com/go/motion

Thanks, John. Great info!

John is correct in that you will have a slight decrease in light (John is the expert here. My experience is just that, experience. Lots I don't know). But, you can always notch up the bulb to compensate. The glass guy I spoke to said if the mirror is laser quality, the image will not suffer. So far, that seems to be the case. Like I said, build all your frames and mounts using simple glass mirrors so when you break them, it's tens of dollars, not hundereds. My port holes are 24x48 and I wish I made 'em a little bigger. I'll try to find the digital cam and post a prototype of the mounts we're using.

I had to use periscopes because to raise the booth would have made it non-ADA and would have required an elevator (don't get me started), So, we did it at "floor" level and used mirrors to get the image up. Given the choice, I would love to not have the mirrors.

Avalon,

I really appreciate all the advice. It is a tough decision. I am trying to avoid using mirrors, but if I can't, I want to do it right. Any pictures you have would be a great help.

Thanks again.

There are some good pictures in the film-tech warehouse under Lowes Cineplex Dupont Circle 5

As John stated, the first surface glass will offer a decrease in light. It seems the higher quality the reflected image, the more light is lost with first surface mirrors. Laser quality glass seems to be cutting it down about 25%, which means I'll be going from a 1k to a 1600 wt bulb. For a piece of 33x25 first surface, lazer quality glass, I'm looking at about $100--roughly 4x more than regualr mirrors. I'll calculate the actual light loss when I get everything set up and post it here.

Avalon,
Curious about how this project is doing. Did you finish any of the calculations mentioned and are there any photos posted anywhere? Thanks. -JRG

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The Parkway Theatre, an idea whose time has come. Help Make it happen!

Sorry to be so long responding. Computer probs. Stay tuned for images. Light loss thru two mirrors and glass is about 25%. Mirrors really are not a solution...

Years ago we did many of the early cineplex locations with front surfaced mirror periscopes and the light loss was over 25% per mirror
also the contrast dropped
all these locations have sinced closed to better theatres so one needs to be carefull presentation and quality is all the exhibitor has to offer compared to other media