Film-Tech Forum ARCHIVE: 35PA

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Posted by Antonio Marcheselli (Member # 373) on 02-05-2002, 05:27 PM:

Hi

I was looking on the Internet to buy some 35PA (RP40) to check our lenses.

I found "35PA 50'" at 180USD

Are 50'=50 inches?
If I'm right, 50' are 127cm...

And what is the 35AT?

Bye
Antonio

Posted by Joe Beres (Member # 678) on 02-05-2002, 05:31 PM:

Antonio,

50 feet actually is 240 inches which equals 1534 centimeters.

I'm not sure what the 35AT is, but I'm sure someone will.

Posted by Pat Moore (Member # 380) on 02-05-2002, 06:50 PM:

Hi;

My calculator comes up with a different answer, Joe. That's a 50 foot roll, which equals 600 inches, which equals (about) 1524.0 cm.

I don't know what "35AT" means, but "35PA-50" means a 50-foot roll of 35mm Projector Alignment Film made according to SMPTE's Recommended Practice (RP) 40.

Pat

Posted by Dave Macaulay (Member # 813) on 02-05-2002, 07:20 PM:

Pat, you don't need the "about". 1 inch is defined as 2.54cm

Even if you hate Metric, your inch is still defined by it

(The meter is defined from some specific wavelength of light)

Posted by Dave Macaulay (Member # 813) on 02-05-2002, 08:03 PM:

Antonio:
That's a 50 foot roll, as you probably already guessed.
The 35AT is anamorphic projector alignment film. I've never used this, the regular "RP40" 35-PA film has enough info to set up anamorphics - so I don't know exactly what it has that I've been missing.
You can buy the test films direct from www.smpte.org.

Shneider has an interesting lens test film as well http://www.schneideroptics.com/projection/cinema_projection/test_film/ - this is useless for setting up projectors and masking but it does give a very good idea of what picture problems your lens and the projection geometry are causing. Don't use this if you have old lenses, especially the shorter focal length older lenses (and can't afford new ones), it's too depressing.

Posted by Joe Beres (Member # 678) on 02-05-2002, 08:26 PM:

Thanks, Pat. I had the same figure, but couldn't type it.

Posted by Rick Long Jr (Member # 541) on 02-05-2002, 08:50 PM:

Anyone else notice that the perfs in RP-40 are different than the perfs in most print stock. They have rounded sides, different from the T.V. screen shaped Kodak Standard perfs. I assume that SMPTE uses these perfs for a reason. So, my stupid question of the day is, why? And why don't other labs use them?
O.K. Two stupid questions.

Posted by Steve Guttag (Member # 268) on 02-05-2002, 08:52 PM:

As some have stated 35-AT is the Anamorphic alignment test film. It's origins go back to the CinemaScope days when there was only 35APAL test film that did not deal with anamorphic at all. The current 35-PA target does indeed have some useful targets for adjusting anamorphic attachments.

35-AT started life being centered on the film-center rather than being offset for the optical track, the current version is offset for the optical track, the original version was on CS-1870 perfs with magnetic stripes, the current version is not (I don't remember if it is on BH-1866 perfs or KS-1870 but I think it is KS-1870). Everything on the 35AT film is geared toward setting up the anamorphic lens...all horizontal elements are compressed by 2:1 so it only looks proportional on a properly set up anamorphic system. 35AT is NOT made to the same standards as 35-PA (RP-40 in street speak) and in fact the target is not perfect, I believe if you project the frame line you will find that the lines do not line up precisely from top to the bottom of the frame.

I disagree on the Schneider test film not being of any value for setting masking and such...it can be used in lieu of the SMPTE test film though it is VERY black so it will soak up your heat energy and possibly cause it to not be reliable if it becomes deformed.

SMPTE also has 35-IQ which is equal lengths of film (100 feet) in Black and White as well as color (only on the magenta layer). The magenta film is on the top layer so focus can be established but it won't soak up the radient energy as much as the B&W version. The color version, I believe, is currently on KS-1870 perforations and is a better representation of feature film stock though the B&W version is certainly easier to see and to set shutter timing to.

Steve

(SMPTE P3 member and currently working on the RP-40 document)

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"Old projectionists never die, they just changeover!"