perforation pitch

[PKM]

Hi guys,

 

Does Kodak 35mm black and white motion picture negative film have a different perforation pitch from Kodak 35mm colour motion picture negative film? I recently bought some of each from a short ends distributor, and the colour runs through my camera (an Arri IIC) fine, while the B&W perforations seem to continuously tear, and the film loses its correct size loop within the camera. The two films would seem to both be new, originating from approximately early this year.

 

The perforations drift by the equivalent of one full perforation over the course of about 6 feet of film (when you hold a strip of the colour against a strip of B &W)

 

Does anyone have any suggestions / explanations?

 

Peter

[Dominic Case]

One perf in six feet is about 0.3% difference. That's a little more than the difference between neg pitch (0.1866") and pos pitch (0.1870"). But there's no reason for the difference unless you have been sold some stock with non-standard perforations. Normally b/w and colour are the same. The label on the can (if it's original) should show you the pitch - look for one of those two numbers.

 

People have sometimes reported difficulties running some types of b/w neg in some cameras - but it seems to be more to do with the built-in lubrication of the film surface that the pitch of the stock.

[Adam Frisch FSF]

Can film shrink?

[John Pytlak RIP]

Can film shrink?

<{POST_SNAPBACK}>

 

Yes, triacetate film can shrink, but it usually takes many years.

[PKM]

Yes, triacetate film can shrink, but it usually takes many years.

<{POST_SNAPBACK}>

 

Hi John,

 

If I did get Kodak B &W (5222) and Kodak Colour (5245) 35mm films from a short ends distributor, and both would seem to have originated from earlier this year, would it be possible that the perforations of one, relative to the other, drift by the equivalent of one full perforation over the course of about 6 feet of film? And again, when I run each roll through - the colour one works, the B & W clearly tears and loses its loop, then back to the colour one, and it works, and then back to the B & W one, and it tears and loses its loop - does this seem possible? I know that on newer cameras than the Arri IIC there are more sophisticated pitch control adjustments that can be made, which are done to make the camera quieter - but should any type of stock completely not run through the camera?

 

Peter

[John Pytlak RIP]

If film were kept in adverse conditions (e.g., hot), it could have shrunk at a faster rate. Unfortunately, short end vendors are at the mercy of their sources, who may not have stored the film properly, or mixed in some really old stock.

[Nate Downes]

I just shot some old stock last weekend, and it's shrunk by around 0.2% at 7 years of age. As I was shooting it soly to test out the camera, no big deal to me. But that is the break of using older filmstock.

[Laurent Andrieux]

Even if 1 perf over 6 feet gives a figure of 0.3 %, I don't like that, and wouldn't be astonished if it was linked to the cause of your troubles...

 

John doesn't take account the fact that some stock can have a manufacturing problem, sometimes.

 

I've had problems with non regular perf on some 35 mm stock once, not enough to occure what you describe, but just enough for having a very bad registration pin test (a big ad that was going telecine + digital post prod !).

 

Did you do this test with your stock, BTW ?

 

Just to reasure John... No, it was not kodak stock ! and what is funny is that the ad's client was... the stock manufacturer ! ;)