Super Geek Question

Tim Carroll · April 5, 2010

Doing some camera work and while checking a number of issues, I happened to mic a piece of fresh Kodak single perf 16mm stock (7219). Always thought it would come in at 16mm (hence the name). And I remembered hearing somewhere that it's tolerance was plus zero, minus two hundredths of a millimeter, which would make it 15.98mm to 16.00mm.

Well this film comes in at 15.93mm, which is noticeably undersized. Anyone else have some fresh stock, and a micrometer, and wouldn't mind checking what you get?

Best,

-Tim

Dominic Case · April 7, 2010

I have neither a fresh piece of stock not a micrometer to hand, but I do have the SMPTE standard SMPTE/ANSI 109.

It says the width of 16mm film is 15.950 ± 0.025 mm. So the minimum width is 15.925mm and your sample is wider than that, so it's OK (though only just - how much is Kodak saving by shaving about 0.15% off the film ;)

There is a note that says "The metric conversion of dimension A is purposely chosen and shown to three decimal places to prevent the maximum width dimension from exceeding 16 mm."

And since you are looking for precision, the standard applies to film at the time of perforating, and at a temperature of 23C and 50%RH. Processed film will shrink very slightly.

Tim Carroll · April 7, 2010

I have neither a fresh piece of stock not a micrometer to hand, but I do have the SMPTE standard SMPTE/ANSI 109.

It says the width of 16mm film is 15.950 ± 0.025 mm. So the minimum width is 15.925mm and your sample is wider than that, so it's OK (though only just - how much is Kodak saving by shaving about 0.15% off the film ;)

There is a note that says "The metric conversion of dimension A is purposely chosen and shown to three decimal places to prevent the maximum width dimension from exceeding 16 mm."

And since you are looking for precision, the standard applies to film at the time of perforating, and at a temperature of 23C and 50%RH. Processed film will shrink very slightly.

Dominic,

Thanks for the SMPTE standard, I couldn't find that when I was searching online.

It's weird, got some 7219 that read 15.923mm, so I guess that is technically too small. It was fresh stock from Kodak, though I'm not sure when it was perforated, so maybe it shrinks while in Kodak's storage. Checked some of the new 7207 and it is definitely wider, coming in at 15.951mm.

Thanks again for the spec.

Best,

-Tim

John Sprung · April 7, 2010

Tim, what are you using that reads down to 0.001 mm? How consistent are the readings?

-- J.S.

Tim Carroll · April 7, 2010

Tim, what are you using that reads down to 0.001 mm? How consistent are the readings?
-- J.S.

Got a really nice micrometer from my engineering career decades ago. It reads down to .0001 inch which works out to about .0025 mm. It's very consistent. That's what I used to gage the film stock. For FFD readings, I have the original ARRI depth gage which actually reads down to .001 mm, very repeatedly, though Axel gives me a hard time about using it. My other FFD gauge reads down to .01 mm, which is what most techs are using these days. Also have an indicator that I use with my surface plate, and that reads consistently down to .002 mm, though I rarely have anything that I need to indicate to that level of accuracy. Needless to say, these were all rather expensive, and all are kept in a special cases, away from moisture and temperature extremes, NOT that I'm anal or anything. :-)

Best,

-Tim

John Sprung · April 7, 2010

Ah, good stuff. Big granite surface plates, Jo blocks, I love it. Out here, auctions have been the best place to pick up machine shop stuff.

-- J.S.

Tim Carroll · April 7, 2010

Ah, good stuff. Big granite surface plates, Jo blocks, I love it. Out here, auctions have been the best place to pick up machine shop stuff.
-- J.S.

If I had the money and the space I could have probably the nicest machine shop on the planet. A large number of machine shops went belly up in Chicago because of the recession, and the auctions have pretty much included any machine your little heart could desire. Beautiful lathes, mills, you name it.

But I do okay with my little mill and my Austrian lathe, and various other shop tools. But it's fun to dream.

Best,

-Tim

David Auner aac · April 19, 2010

But I do okay with my little mill and my Austrian lathe, and various other shop tools. But it's fun to dream.

Austrian lathe? Emco?

Regards, Dave

Simon Wyss · April 19, 2010

Cameras are built to handle raw stock of between 16,00 and 15,85 millimeters. Check whether your camera's lateral guidance makes that much movement. It should.

Matters become complicated with printing. Most continuous printers guide the films by meshing teeth in the perforation, so a film's actual width falls out of the subject. Step printers will have a lateral spring-loaded guide rail and lengthwise acting mechanism in most cases. Some precision intermittent printers guide via the perf only (two fitting pins one or the other way).

Projectors and scanners should eat film like cameras plus the heat complication.

Tim Carroll · April 19, 2010

Austrian lathe? Emco?

Regards, Dave

Yep, nice little unit.

Best,

-Tim

John Sprung · April 19, 2010

What I've got is a Benchmaster mill and a 12x36 Atlas/Clausing lathe, both pre-WWII.

-- J.S.

Simon Wyss · April 19, 2010

ISO 69 reads: measure A (strip width) 0.628 ± 0.0010 in/15,95 ± 0,025 mm ( . . . ) safety raw stock film as described in ISO/R 543, immediately after cutting and perforating. ( . . . ) Experience shows that it is common for film to expand when exposed to high relative humidity. Allowance should be made for this factor in equipment design and in no case should equipment fail to accomodate a film width of 16,00 mm (0.630 in).

Tim Carroll · April 19, 2010

What I've got is a Benchmaster mill and a 12x36 Atlas/Clausing lathe, both pre-WWII.
-- J.S.

John,

The shop we had in engineering school had a couple of Clausings, I loved working on those. Give me a Clausing lathe and a Bridgeport mill, and I'm as happy as a pig in s*#t.

Best,

-Tim