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Topic: Scope Aperture Plate question

John Hawkinson
Film God

Posts: 2273
From: Cambridge, MA, USA
Registered: Feb 2002

posted 11-15-2004 12:29 AM

Let me be more clear how I use a caliper, since I've inadvertantly caused so much confusion. [uhoh]

For each of the 4 sides:

Run RP40 to see where to file the plate to. Remember that each square is .004125".
Measure the current opening in your plate with the caliper.
Open up plate (file, nibbler, etc.) to about .015" under the target value. This is where the caliper shines, since you know exactly how far you've gone.
Test the plate, fine-tune with file.

Gordon says "A caliper will only tell you the size of the opening not its relative position." That's not quite true. If you know the offset from the outside edge of the plate to the optical center, then you know the relative position. And assuming you start out with an unfiled plate where the opening is centered (or are using a projector with symmetric plates, etc.), then you're all good. Just measure from the outside top of the plate to the inside of the aperture hole. But if you do one side at a time, keeping track of the relative position isn't so important anymore (or two adjacent sides around a corner from each other).

Frank asks how you use a caliper for keystone compensation. You can determine the correct numerical keystone compensation (by watching the RP40) and then file to that, or you can just do the keystone compensation with the usual slow iterative process (i.e. "you don't").

I think the key point here is that the caliper is a tool to let you get within the ballpark of the right size easily, without going too far. It is not a tool for fine-tuning the cut, because there are too many variables that are quite difficult to measure numerically. I didn't mean to imply otherwise, and I'm sorry if my sloppy wording initially lead people astray.

By the way, Bill Hooper, your sample aperture plate is upside down.
--jhawk

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Monte L Fullmer
Film God

Posts: 8367
From: Nampa, Idaho, USA
Registered: Nov 2004

posted 11-30-2004 03:52 AM

True. Wasn't SuperScope (2.00/1) ratio where RKO and a small host of others had a bunch of features shot with the VistaVision horizontal film path process (prob used Mitchell "elephant ears" cameras), then the film was masked down and processed in the 2 to 1 squeezed anamporphic - so to keep the "depth of field" in a wide screen presentation that the actual anamporphic camera lens would lose?

Theatre I worked at years ago had a set of the .650 x.650 SuperScope apertures for our "XL's", and masking settings for the SuperScope presentations. thx-Monte

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Stephen Furley
Film God

Posts: 3059
From: Coulsdon, Croydon, England
Registered: May 2002

posted 11-30-2004 04:21 AM

Superscope was shot as normal 4-perf, and the frame was masked down to 2:1 and then given a 2x vertical stretch in the lab. Not unlike Super 35, but the negative frame did not extend into the track area, as it does with Super 35.

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John Pytlak
Film God

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

posted 11-30-2004 07:56 AM

Standard SMPTE 195-2000 "recognizes" the following aspect ratios in current use:

2.39:1
1.85:1
1.66:1
1.37:1

quote:
A.4 Typical aspect ratios for nonanamorphic theatrical projection
For aesthetic and practical reasons, theatrical projection
may present 35-mm images in such a manner that the full
width of the projectable area is shown but the projected
height is less than maximum. Photography designed primarily
for theatrical exhibition recognizes this and is composed
for the more elongated rectangles. Several aspect ratios for
the final projected picture are recognized through usage
(see table A.1).

Caring About Composition

quote:
SMPTE Standard 195 "Motion-Picture Prints--Projectable Image Area" specifies the film area intended for projection. The dimensions specified are as follows:

Aspect Ratio · Lens · Width (In.) · Height (In.) · Width (mm) · Height (mm)
2.39:1 · Anam · 0.825 · 0.690 · 20.96 · 17.53
1.85:1 · Flat · 0.825 · 0.446 · 20.96 · 11.33
1.66:1 · Flat · 0.825 · 0.497 · 20.96 · 12.62
1.37:1 · Flat · 0.825 · 0.602 · 20.96 · 15.29

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