Film-Tech Forum ARCHIVE: Are scope and 1:85 frames printed differently?

This is topic Are scope and 1:85 frames printed differently? in forum Film Handlers' Forum at Film-Tech Forum ARCHIVE.

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Posted by Greg Mueller (Member # 17) on 01-04-2001, 08:55 AM:

When I run a scope film and RP40, the center of the frame is correct. Then when I change to 1:85 I have to move the frame up on the screen. Why is that?

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Greg Mueller
Amateur Astronomer, Machinist, Filmnut

Posted by Adam Martin (Member # 641) on 01-04-2001, 09:00 AM:

The lens offset adjustment is incorrect. What projector is it? (Oh, and are they fixed lenses or on a turret?)

Posted by Greg Mueller (Member # 17) on 01-04-2001, 09:04 AM:

It's a DP70. You can just see it peeking around the right side of the picture. I'm using Schneider optics. There's no turret

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Greg Mueller
Amateur Astronomer, Machinist, Filmnut

Posted by Adam Martin (Member # 641) on 01-04-2001, 09:40 AM:

Well, it's been a while since I've used a Norelco, so someone stop me if I'm wrong.

Does the lens collar rotate to a 180 degree position? (In 35/70 projectors, the lens needs to be centered on the film frame for 70mm mag and offset for 35mm optical to accommodate the soundtrack) This would be a side-to-side offset.

If you remove the lens from the projector lensmount, the collar usually will have three set screws around the outside near the center of the collar that are used to tighten the pressure plates that hold the lens. These can sometimes be used to adjust how the lens is centered in the collar and, thus, on the screen. Just loosen one and tighten the other two to nudge the lens. >>Do this at the workbench, so you don't drop the lens! << Put it back in the projector and see what happened. Take note, however, that if the collar is slid forward or back on the lens, it will significantly change the focus, and you want both lenses to be at the same focal point so you don't have to adjust too much after a lens change (especially if it's during a show).

Like I said, it's been a while, so someone else can feel free to chime in!

Posted by Greg Mueller (Member # 17) on 01-04-2001, 09:48 AM:

Yes the lens rotates. There are two collars one inside the other. I'll try your suggestion, thanks.

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Greg Mueller
Amateur Astronomer, Machinist, Filmnut

Posted by Gordon McLeod (Member # 33) on 01-04-2001, 11:34 AM:

typically there is printer differences as the source of the problem

Posted by John Walsh (Member # 168) on 01-04-2001, 12:02 PM:

You probably thought of this, but do you have adjustable top masking? If you do, that would you to move the framer to re-center the image.

How far is it off?

(If it's only off a little) I have found some of those 5" to 2 25/32" lens bushings are machined poorly. Sometimes by rotating the bushing, you can get it to hold the scope lens in the same plane as the flat lens.

With the shorter focal length lenses used nowadays, I've seen where the lens has to be positioned so close to the film, that only the front 1/2" or so gets clamped into the bushing; which means it doesn't get clamped "straight." They sell screw-on lens extention collars for that.

(If it is off a lot) On some projectors (Simplex) you buy one bushing for 35mm use and another for 70mm use. They both are 5" to 2 25/32" bushings, but the hole in the 70mm one is offset to center the lens for 70mm film. Usually the 70mm bushing is painted red, but I got one that wasn't.

If I remember, the bushing that comes with a DP70 was a type where one screw clamps a "C" shaped section inside the bushing.

Normally, I would agree with Gordon; but in this case I'm assuming that the RP40 test film is being used to project and test flat and scope. (Otherwise, Gordon is right) I would not use regular film to tell if the flat and scope images are correct.

Posted by John Pytlak (Member # 331) on 01-04-2001, 12:05 PM:

Gordon --- it is likely a lens alignment issue, as I believe Greg is projecting the SAME piece of SMPTE 35-PA (RP40) to evaluate both formats.

I agree that the printer can introduce a vertical shift (especially bi-directional printers), but that wouldn't be particular to scope vs. flat. And Super-35 extraction to scope would depend on the setup by the optical printer operator.

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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

Posted by Greg Mueller (Member # 17) on 01-04-2001, 12:39 PM:

It's only off a bit. Maybe an 1/16 to 1/8 of a turn of the framing knob. I'll pull the flat lens and put an extension on it and check the adapter.

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Greg Mueller
Amateur Astronomer, Machinist, Filmnut

Posted by Greg Mueller (Member # 17) on 01-04-2001, 02:22 PM:

I was able to work out about half the difference. The 1:85 lens holder was a smidge eccentric, and I got some mileage there. I messed with the scope lens too, but couldn't get anything. There is still a bit of difference, but I think I can live with it.
Thanks for the help y'all

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Greg Mueller
Amateur Astronomer, Machinist, Filmnut

Posted by Randy Stankey (Member # 64) on 01-04-2001, 08:21 PM:

I have seen some sloppy aperture plate jobs.

The guy who did them messed up and just reframed and adjusted the turret to compensate. I checked it by shutting down the projector and looking into the aperture. There WAS a framing difference between F and S!

Not that I'm saying YOU are sloppy... just an idea.

Posted by Greg Mueller (Member # 17) on 01-04-2001, 09:38 PM:

What I did as a test was, I ran a loop of RP40 with the scope lens in and centered the picture up by looking at the top and bottom masking (it doesn't move) then I ran the RP40 with the 1:85 lens and noted that the center of the picture was lower, according to the markings at top and bottom. By fiddling with the eccentricness of the 1:85 holder I was able to raise the picture up about half of the difference in the two center positions. I haven't run any film through it yet but I'm betting the difference won't be noticeable. (I hope) If it is I'll refiddle with it.

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Greg Mueller
Amateur Astronomer, Machinist, Filmnut