Film-Tech Forum ARCHIVE: Clear optical port glass

This is topic Clear optical port glass in forum Film Handlers' Forum at Film-Tech Forum ARCHIVE.

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Posted by Lowell Peterson (Member # 60) on 11-05-1999, 02:13 AM:

Does anyone know a good source of clear optical glass for port windows?

Thanks,

Lowell Peterson
lowell@peterson.net

Posted by Scott Ribbens (Member # 180) on 11-05-1999, 02:46 AM:

You could try TCI at www.tcioptics.com

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Scott

Posted by Scott Ribbens (Member # 180) on 11-05-1999, 03:07 AM:

I just tried that site, and it might be a better idea to call them to request specifics, or email them. There does not seem to be much real info here.
email is: mailbox@tcioptics.com
phone is (516)436-5900 (New York).
you might even be better off if you contact Len-D Enterprises, Inc. No email or website but the phone is (561) 682-3500. I think that Len-D distributes port glass for TCI. I'm just getting this info off of some literature I got at the last ShoWest. I also have a sample that I got from them. Good stuff.
-----
Scott

Posted by John Pytlak (Member # 331) on 11-05-1999, 07:36 AM:

The TCI port glass is distributed by Len-D Enterprises, Inc., 6080 Okeechobee Boulevard, West Palm Beach, Florida, 33417, telephone: 561-682-3500, fax: 561-682-3777. It is claimed to be optical quality, spectrally neutral, with 99% transmission, and less than 1% reflectance. Contact is Lenny Dickstein, E-mail: LenEnterprises@yahoo.com

Kelmar Systems Inc., 284 Broadway, Huntington Station, New York, 11746, telephone: 516-421-1230, fax: 516-421-1274, http://www.kelmarsystems.com also carries a line of porthole wall assemblies and optical quality port glass. Contact is Andy Marglin.

Goldberg Brothers, Inc., 8000 East 40th Avenue, Denver, Colorado, 80207, telephone: 303-321-1099, fax: 303-388-0749, carries a line of port glass frames and optical anti-reflection glass.

You should also check with your theatre equipment dealer to see what they carry.

My next article in Film Notes for Reel People discusses the importance of reducing stray light and optical flare to improve screen contrast. Having clean, properly-installed, optical quality, anti-reflection port glass is critical.

------------------
John Pytlak, Senior Technical Specialist
Worldwide Technical Services, Professional Motion Imaging
Research Labs, Building 69, Room 7419
Eastman Kodak Company
Rochester, NY 14650-1922 USA
Tel: 716-477-5325 Fax: 716-722-7243

Posted by Steve Guttag (Member # 268) on 11-05-1999, 10:18 AM:

Schneider Optics is now distributing "projection quality" port glass with anti-reflective coating.

Watch out on the various glass listed in John's post. There are MANY MANY various grades of glass having to do with their purity and actual manufacture.

One quick check is to look at the edge of the glass, it shouldn't be very green (preferrably not green at all) and compare with the same thicknesses. While looking at the edge, check how consistant it is...if you see waves in it...you picture will suffer.

I have used Goldberg's glass with very good results. Even the non-coated glass is much more clear than glass-shop plate.

Steve

Posted by Aaron Sisemore (Member # 145) on 11-06-1999, 03:38 AM:

Another place to try would be OCLI, I have ha d a few one-off pieces of 99.999% nonreflective glass made for portholes for a couple of special applications http://ocli.com

Posted by John Walsh (Member # 168) on 11-14-1999, 02:00 PM:

Sorry to bring this up again.....

I talked to the THX people about optical glass. They suggested several people, and one of those were Abrisa Industrial Glass (909) 698-8469.

I talked to a guy there who was very helpful, and sent me some samples. I held the samples in front of the image and it was pretty amazing how little reflection there was compaired to the regular glass. Not only good for the image but, if you have a problem where the light reflects off of one port window and shines out where you don't want it to, this would cure that also.

They offer two thickness'; 1/4" and 3/8." (THX suggests two panes of glass, one 1/4" and the other 3/8.") Also, Abrisa offers two different grades ("Clearview" and Clearview Plus".)

The price breakdown was this:

Clearview 1/4" $0.27 per sq inch
Clearview 3/8" $0.33 per sq inch
Clearview Plus 1/4" $0.84 per sq inch
Clearview Plus 3/8" $0.86 per sq inch

While it's too expensive for us to do all screens, it's is do-able for our main auditouriums.

Posted by Gordon McLeod (Member # 33) on 11-15-1999, 09:54 AM:

glass fab in rochester also has port glass

Posted by Mike Blakesley (Member # 26) on 11-15-1999, 12:12 PM:

John P. (or anyone else),

Can you go into a little more detail about "properly installed" port glass?

Meaning, what are the criteria for proper installation?

Posted by John Walsh (Member # 168) on 11-15-1999, 04:23 PM:

"Properly installed" port glass is one of those little projection details about which everybody seems to have an opinion on. This was a topic at r.a.m.t. awhile ago, and I can just recopy what I learned from THX here:

THX suggests that the two peices of glass be mounted on an angle for the projector port. If you are in the booth looking out, the top of the inside peice should tilt out (towards the aud) 7 deg. The top of the outside peice should tilt in (away from the aud) 7 deg. So if the projector is at a zero angle, the glass would be as described. There is always a 14 deg angle between the two peices of glass.

If the projector is tilted down 5 deg, then the inside glass tilts forward 12 deg, and the outside glass tilts back 2 deg.

If you go any less than the 14 deg difference, you'll get weird reflections that bounce back and forth, shining on peoples head below. Don't ask how I know.

The fellow I talked to (at THX) said somthing a bit odd; He explained that the two peices of glass be of different thickenss. He suggested that one peice be 1/4 inch thick,
and the other 3/8 inch. He said that if both peices were the same thickness, one peice might vibrate, and transmit that to the other peice. At certain harmonic frequencies, one of the peices of glass could crack. Two different thickness of glass would help keep "resonating" from occuring.

THX will fax you a picture showing the port and the wall insulation.

The viewing port does not have to be on angles, but they do want two peices of glass for sound insulation.

For both ports, an opening in the wall is framed with 2x4's or 2x6's. You would have ready a pre-made port window, just like when putting in a regular window in a house (we had our candy-stand guy make ours). The opening in the wall is about one full inch bigger than the pre-made port window. You squirt acoustical cauking all around the frame, and ooze in the window. Then shim it so it stays centered. The idea is to have it "floating" within the frame. Seal up the outside gaps with more cauk.

Posted by Greg Mueller (Member # 17) on 11-22-1999, 09:22 AM:

I've been trying to order glass from LenD since the contact info appeared here. Two phone calls and an email and still no response. Might want to try another source.

Posted by Lowell Peterson (Member # 60) on 11-22-1999, 01:12 PM:

I also got no reply from Len-D. I ended up buying from Goldberg Brothers, who were very helpful, with a good price.

Posted by Greg Mueller (Member # 17) on 11-22-1999, 03:41 PM:

The guy at "Abrisa" has a $250 minimum on his orders, so one piece of Port Glass gets real expensive.

Posted by John Walsh (Member # 168) on 11-22-1999, 03:50 PM:

"The guy at "Abrisa" has a $250 minimum on his orders, so one piece of Port Glass gets real expensive."

Ah, I didn't know that. I asked for a price on several peices, and went beyond the minimum.

Still, I don't think that's too unreasonable for a specialty item like optical port glass.

Posted by John Pytlak (Member # 331) on 11-23-1999, 08:24 AM:

I agree with the advice from THX. Most important things are to use optical quality glass with anti-refection coatings, and properly angle the glass so light doesn't get re-reflected back into the optical system. The idea of using two different thicknesses to avoid harmonic vibration is valid.

My next article for "Film Notes for Reel People" is about improving screen contrast, and proper selection and use of port glass is a major part of reducing stray light. Dirty port glass is one of the biggest projection "sins" I see when visiting theatres. One way of looking at it is that the port glass is really the front-most element of the projection lens, and needs to be kept absolutely clean and scratch-free. Ideally, the port glass should be so invisible, that you should be barely able to see the image reflected by it.

Posted by Scott Ribbens (Member # 180) on 01-17-2000, 05:51 PM:

Just a post to put this up by the other port glass thread.

Posted by Rick Uhlhorn (Member # 198) on 01-19-2000, 01:49 AM:

find some glass out of old copy machines. clear as a bell.

Posted by John Pytlak (Member # 331) on 01-19-2000, 10:32 AM:

The idea of finding glass from an old photocopier is a reasonable one. It is likely to be optical quality (wouldn't want make a million copies of a bubble or internal defect in the glass), and very well may have anti-reflection coatings. Glass that is anti-reflection coated usually has a slightly dichroic appearance by reflected light, such that the reflection of a light source has a slight color shift when viewed at an oblique angle. It might be a problem finding enough old copiers to outfit all the ports in a 20-plex, and I doubt they will be free. Another concern would be finding glass from old copiers that hadn't been permanently scratched or damaged after years of use, especially the delicate anti-reflection coating. "Caveat emptor", "Let the buyer beware". I'd recommend sticking with the established suppliers, unless you know exactly what you're looking for.