Film-Tech Forum ARCHIVE: Film Temperature

This is topic Film Temperature in forum Film Handlers' Forum at Film-Tech Forum ARCHIVE.

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Posted by Bill Enos (Member # 440) on 03-02-2002, 08:36 AM:

A friend bought an infrared thermometer recently, among the things we measured the temp of was film. Projector is Simplex XL with scope aperture in place, lamp was 3000 watt running at 92 amps. The machine had been running for about 40 minutes. Film entering the projector was 71F. Exit it was 95 degrees on frames that were very clear outside scenes and 106 degrees F on very dark frames. Most of the rise I guess is from the light, but some has to be from contact with hot surfaces. Temp. of the aperture plastic handle was 166.

Posted by Steve Kraus (Member # 476) on 03-02-2002, 09:52 AM:

Cool! (Sorry; couldn't resist the pun.)

I've never measured temperatures but the readings seem reasonable. Where were you reading the "after" film temp? I remember once running a B&W silent film at 20 fps, 4kW, no heat filter and the film would literally burn your hand coming out of the gate. Let it slip between two fingers and you didn't feel it at first (not much thermal mass to convey heat with) but after a few seconds you had to let go it was that hot. (As you probably know, color film is much better in this respect because it is mostly transparent to the IR component of the light beam which sails right through so most of the heating is caused by those parts of the visible spectrum that are being filtered out and converted to heat.)

Can you get a spot reading in the middle of the film? That would not have contacted gate & trap or sprockets and would be less likely to be effected by such external factors.

Posted by John Pytlak (Member # 331) on 03-02-2002, 01:46 PM:

Kodak published a very definitive study of the effects of radiant energy on both color and B&W prints:

"Projection Performance of Theatrical Motion-Picture
Films Using Xenon Short-Arc Lamps", Paul H. Preo, 92:938, Sept. 1983 SMPTE Journal

Here are links to my articles in Kodak's "Film Notes for Reel People":
http://www.kodak.com/country/US/en/motion/newsletters/reel/fall97/pytlak.shtml
http://www.kodak.com/country/US/en/motion/newsletters/reel/winter97/projection.shtml

------------------
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

Posted by Bill Enos (Member # 440) on 03-02-2002, 03:15 PM:

Film temp. was measured as it was leaving the sound head. We'll see what the temp. is before contact with the sound drum tonite if possible. There is no heat filter but the reflectors are dichroic. (check spelling please)

Posted by Steve Kraus (Member # 476) on 03-03-2002, 11:16 AM:

Now that Scott is in charge and this place will go hog wild have you thought about taking the IR thermometer to a singles bar and scanning the distaff* to see which ones warm to the sight of you?

* that means females

Obligatory O.T. content: I think full contact with a metal sounddrum is having an enormous impact on temperature. Probably sucks the heat right out.

Posted by Christopher Seo (Member # 7) on 03-03-2002, 01:51 PM:

Bill,

Out of curiosity, what make/model IR thermometer are you using? I've got a Fluke 80T-IR probe, for use with their digital multimeters, and I might just try this myself for the fun of it.

Posted by Josh Jones (Member # 447) on 03-03-2002, 03:00 PM:

Wouldnt it be impossible to get an accurate reading through the aperature because the infared energy of the lamp would throw off your reading? Unless you could get a reading while the shutter is closed. You would still get an incorrect reading because the gate parts and shutter blades would be giving off infared energy because they are hot too. Any one else have any other ideas?

Josh

Posted by John Pytlak (Member # 331) on 03-03-2002, 03:44 PM:

One idea would be to apply "Tempil Stik" or "Tempilaq-G" to the emulsion side of opaque film, and see which temperature grade melts:
http://www.tempil.com/
http://www.tempil.com/Tempilstik.htm
http://www.tempil.com/TempilaqG.htm

Some color print films can be damaged by emulsion temperatures much above 160 Celsius. Kodak VISION Color Print is very resistant to heat damage, withstanding well over 200 Celsius. Permanent heat damage on a color print first shows up as an opalescent spot, that by reflected light appears magenta from the emulsion side, and yellow-green from the back side. On the screen, a "frosty" or "spidery" pattern might appear in dark scenes, especially in the "hot spot" of the projector lamp.