Film-Tech Forum ARCHIVE: Aperture Plates

my profile | my password | search | faq & rules | forum home

»	Film-Tech Forum ARCHIVE » Operations » Film Handlers' Forum » Aperture Plates

Author

Topic: Aperture Plates

Greg Kristopik
Film Handler

Posts: 15
From: Los Angeles, CA
Registered: Sep 2000

posted 02-14-2001 04:00 PM

I know this should be something I should know, but can anyone help me with this slight problem.

When I slide the apeture plate over, there is still a small black fuzzy bar on the left hand side next to the masking that won't budge anymore. I tried the adjusting the turret and moved the lens from falt to scope but to no avail.

Any tips???
Thanks a million in advance!

Jerry Chase
Phenomenal Film Handler

Posts: 1068
From: Margate, FL, USA
Registered: Nov 2000

posted 02-14-2001 04:31 PM

Any chance the projector got bumped out of alignment? It does happen, and if nothing else has changed, it could be a possibility.

Dustin Mitchell
Phenomenal Film Handler

Posts: 1865
From: Mondovi, WI, USA
Registered: Mar 2000

posted 02-14-2001 04:53 PM

Is the gate dirty (probably not, but doesn't hurt to ask)? Other than that I agree with Jerry. If the projector is out of alignment, you can probably kick it back in place with your foot (NOTE: BE CAREFULL! When I say 'kick' you may just have to tap).

Darryl Spicer
Film God

Posts: 3250
From: Lexington, KY, USA
Registered: Dec 2000

posted 02-14-2001 05:28 PM

Have you had your booth floors stripped and waxed recently? A buffer can push the projector over very easily. Is your lens turret mounted on a simplex head (is it a TU2000 model turret). These turets have a lens barrel adjustment that can be made. It is located on the right side of the lens that is in use. It can be adjusted useing a screw driver making a slight turn will adjust the lens barrel over. Note if you are having the same problem with both lenses then it is most likely that the projector has moved slightly.

Randy Stankey
Film God

Posts: 6539
From: Erie, Pennsylvania
Registered: Jun 99

posted 02-14-2001 05:29 PM

What kind of projector is it? Some projectors have adjustable aperture plate stops. (Century SA and Simplex Millenniums come to mind.)

Take a look at the screen when you're running a loop of test film. (PA-35 / RP-40) The diamond in the center of the test pattern should be in the center of the screen. Caveat -- The guy who did the primary installation might not have aligned the projector very carefully so use your head here. Even so, the diamond should STILL be pretty darned close to the center of the screen.

If the test pattern isn't centered and you can't use the lens adjustment to get it back on-center you might have to move the projector. What kind of projector base do you have? May I suggest you take a piece of wood (like a 2 X 4) and place it up against a SOLID part of the projector base and TAP on it with a sledge hammer. Don't do this if you think it'll damage anything. We did this with big CFS consoles. They have big skid plates on the bottom that can take a fair amount of force.

So... you have the projector on-center. I assume you know that there is an adjustment in the lens, since you mentioned that. Then, there is sometimes an "eccentric" stop screw on the trap that allows fine adjustment of the aperture plate from side to side. There ought to be one for FLAT and one for SCOPE. Sometimes it's an eccentric (like in Century) Sometimes it's just an allen screw (like in Simplex PR-2000) Use test film and tinker with those stops until you get it all lined up again. This might take a few minutes. It can be a pain in the butt to do because a fraction of a turn of a screw can make a huge difference in position.

Brad Miller
Administrator

Posts: 17775
From: Plano, TX (36.2 miles NW of Rockwall)
Registered: May 99

posted 02-14-2001 06:41 PM

Not only do we need to know what kind of projector (and vintage) you have, but does it have a lens turret on it?

John Walsh
Film God

Posts: 2490
From: Connecticut, USA, Earth, Milky Way
Registered: Oct 1999

posted 02-14-2001 09:08 PM

Many years ago, we tripled a theater. The projector shined out over a ceiling that was added. Later, when we were filing plates, there was a shadow on the bottom we could not "file away." We kept filing, checking the optical path, looking at the edges of the gate, making sure the image cleared the port window, etc. .... until we realised that the image was hitting the bottom of the new wall outside. So, your problem may not be at the projector.

I know this sounds like annoying "offical" talk, but.. you really should get a short length of test film and run it. The cutout in apertures (even factory-fresh ones) can not always be trusted to be correct.

Richard Hamilton
Phenomenal Film Handler

Posts: 1341
From: Evansville, Indiana
Registered: Jan 2000

posted 02-14-2001 09:09 PM

From what you wrote, you have a fuzzy edge on the left side in both formats. What kind of movable masking do you have? Top, bottom, or side movable? Is the picture overshooting on the right hand masking?

John Pytlak
Film God

Posts: 9987
From: Rochester, NY 14650-1922
Registered: Jan 2000

posted 02-15-2001 07:27 AM

I agree the most likely problem is that the projector was shifted off center. Using the SMPTE 35-PA (RP 40) test film, first verify that the entire image area (0.825 x 0.690 inches for scope, 0.825 x 0.446 inches for 1.85:1 flat) is being projected, regardless of the position on the screen/masking. Then, move the projector or adjust the lens centering to center the image on the screen, and adjust the masking stops to clearly define the image edges. Remember, the projected image should just overfill the masked area on the screen, so the "fuzzy edges" fall on the black masking.

------------------
John P. Pytlak, Senior Technical Specialist
Worldwide Technical Services, Entertainment Imaging
Eastman Kodak Company
Research Labs, Building 69, Room 7419
Rochester, New York, 14650-1922 USA
Tel: 716-477-5325 Cell: 716-781-4036 Fax: 716-722-7243
E-Mail: john.pytlak@kodak.com
Web site: http://www.kodak.com/go/motion

All times are Central (GMT -6:00)

Printer-friendly view of this topic

The Film-Tech Forums are designed for various members related to the cinema industry to express their opinions, viewpoints and testimonials on various products, services and events based upon speculation, personal knowledge and factual information through use, therefore all views represented here allow no liability upon the publishers of this web site and the owners of said views assume no liability for any ill will resulting from these postings. The posts made here are for educational as well as entertainment purposes and as such anyone viewing this portion of the website must accept these views as statements of the author of that opinion and agrees to release the authors from any and all liability.