I agree that Plexiglas and Lexan are not the best choice for port "glass". They scratch easily, and may introduce considerable flare, reducing image contrast. The suggestion of finding anti-reflection coated glass from old copiers is a good one.

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John P. Pytlak, Senior Technical Specialist
Worldwide Technical Services, Entertainment Imaging
Research Labs, Building 69, Room 7525A
Rochester, New York, 14650-1922 USA
Tel: +1 585 477 5325 Cell: +1 585 781 4036 Fax: +1 585 722 7243
e-mail: john.pytlak@kodak.com
Web site: http://www.kodak.com/go/motion

Thing is, I looked at the glass on both our big expensive copier and a retired scanner and the glass in neither looks like it's coated -- at least not as I can tell just by eyeballing it. I wonder if there is the same need in the scanner application for coated glass as there is for projection. I'll see if there are any more technical details somewhere on the manufacturers' websites. The other thing I notice, although I haven't yet dismantled the scanner, is that it doesn't seem like the glass is as thick as port glass. That would bother me as we only use a single piece, not double.

I'll report back when I find out some more.

I was impressed with the glass cleaner from General Motors, so I decided to use it along with newsprint.

In Toronto, there are four main papers.
The Globe and Mail is read by those who run the province.
The Toronto Daily Star is read by those who think someone else should run the province.
The Financial Times is read by those who own the province.
The readers of the Toronto Sun don't give a damn who runs the province as long as the Sunshine girl on page 3 has large breasts.

I chose the Sun.

I made up a loop from a discarded trailer (to protect the lens) ran the projector with lamp, and proceeded to the auditorium. Thanks to the "brilliant" design of the non-opening ports in this particular theatre, I was forced to grab an 8 ft. ladder in route.

The picture being projected through the port-hole showed any spots I might other-wise have missed. I used the FLAT lens btw (which provided the largest image on the port glass).

Spraying the automotive glass cleaner and then scrubbing the port glass, I then let it begin to dry, and followed up with a fresh piece of newsprint.

In the booth, with the picture still running, I repeated the process (being careful not to let any of the spray hit the projection lens).

I was pleasantly surprised with the results. I had a much clearer port than I had been formerly able to achieve with Windex and Bounty.

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Now the question is, can I use ANY infrared filter, such as that sold by Edmund Scientific? Or is there some special deal with the filters in these higher wattage lamphouses? As I recall the ones sold by the manufacturer were fairly expensive and the price is by size. So what would be the problem taking a smaller piece and placing it closer to the aperture, say just behind the shutter (we're using Century DAWs) -- that would require a smaller and therefore less expensive piece. But of course a smaller piece probably won't deal with the infrared as well as a large one, right?

An auxillary dichroic heat filter should reflect the invisible infrared energy (>700 nanometres) to a heatsink, whilst passing the visible light (400 to 700 nanometres) to illuminate the film. As the power is increased or the size of the beam decreased, the heat load on the filter (watts per square millimetre of area) increases, and the base material of the filter needs to be able to withstand the heating. Usually, quartz or PYREX glass are used. Common optical glass is more likely to break, as its thermal expansion coefficient is greater. The filter should NOT be mounted rigidly, as it needs room to expand and contract with heating and cooling. With dichroic filters, the angle of reflection is critical to the "cutoff" wavelength, and needs to be specified.

------------------
John P. Pytlak, Senior Technical Specialist
Worldwide Technical Services, Entertainment Imaging
Research Labs, Building 69, Room 7525A
Rochester, New York, 14650-1922 USA
Tel: +1 585 477 5325 Cell: +1 585 781 4036 Fax: +1 585 722 7243
e-mail: john.pytlak@kodak.com
Web site: http://www.kodak.com/go/motion

So from what you are saying, the filter can be either an absorbing filter that absorbs infrared and passes white, or it can be a dichroic filter that reflects infrared and passes white. I wish I new which one we were getting (they are replacing the broken one -- new filter (costs over $400). If it is a dichoric, then you are saying the angle at which it is installed has to be precise? I am assuming ORCON's filter slots are designed so that will happen if it is dichroic. My gut tells me these are not, only because they don't look anything like a dichroic reflector glass material, but reflectors are a different animal, so that might not apply. Plus, I don't see any obvious heat sink.

To get the filter holder in place, I simply slid the lamphouse back a quarter of an inch so I could stick heat filter unit in between the ORCON exit cone and the docking cone of the Century, then refocus the bulb a tad, and we were in business.

Here's an intersting aside -- one of the reels of SPEEDY, which was a near mint print, except for 3 or 4 accordian splices at each of the reel joints (who teaches these people how to splice?), about a half of the third reel changed from B&W stock to color stock and had tinted sequences. At first I though, well, this was intended and done to recreate the original tinted presentation. But that can't be because why wouldn't the rest of the film be tinted? My guess is that a section of that reel was damaged and they replaced it with footage from another version where color film was used. Is anyone familiar with this title -- did it have a few tinted sections and most of the rest of the film was in B&W? It certainly was disconcerting, all of a sudden seeing color. And it is amazing how we forget how good B&W looks -- I mean really sharp as a tack -- then <SPLICE> and there's color -- not exactly soft focus, but not as crisp as the B&W either. Ah, how much those other two emulsion layers change the apparent resolution. I was very glad it switched back to B&W for the last reel.

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