Super 8 cartridge pressure pad weight

[Erkan Umut]

Hi Folks,

 

I am wondering what is the Super 8 cartridge pressure pad weight (in grams). Do you have any info regarding those rare figures?

 

Also, may the polyester based new stocks cause problems in Super 8 cameras? Is any adjustment necessary for the pressure pad weight for thinner polyester film?

 

Thank you very much for any info!

 

Erkan

Edited April 28, 2013 by Erkan Umut

[Dom Jaeger]

Just from measuring the pressure on a cartridge it appears to be about 150 grams.

 

But the pressure plate in a S8 cartridge doesn't actually press on the film, it presses against outer rails on the camera gate that are raised slightly above the inner film transport rails, creating a film channel that is a few hundredths of a mm thicker than the film.

 

So thinner polyester-based film could be susceptible to a little 'focus breathing' perhaps. Just how much thinner is it exactly?

 

[Andries Molenaar]

The rims on the gate-aperture are for guiding the cartridge plate. It would not work with standard thickness either. It cannot be that precise. Of course it presses the film itself. The friction of the plate is the essence to make the film stand still when the claw is not pushing the film. The pull of the wind-up would always move the film and all frames would be blurred.

[Dom Jaeger]

Actually what would be difficult would be to mass produce cheap plastic pressure plates with a smooth enough surface and precise enough pressure to press against the film and still allow the tiny spring-loaded claw to properly perform a pulldown without slipping or tearing perfs. Try pushing down a S8 pressure pad and sliding the film over it with your finger, it's horribly sticky. The pressure of a Standard 8 pressure plate that does actually press on the film (with a highly polished metal surface and twice the width) is only about 50 grams.

 

The reason S8 film isn't constantly pulled through by the take-up and blurring every frame is in the cartridge design and the take-up clutch. Within the cartridge the film bends sharply around a pin before being taken up, which provides enough resistance to make the take-up spindle slip until the claw feeds another frame of film through and relieves the friction going around the pin.

 

The outer rails in the gate guide the film but at certain points also rest upon the plastic tabs in the cartridge pressure pad that extend out either side of the film at the gate aperture and also (looking at the cartridge) at top right and bottom left. You will find cutouts at these positions in the taller, sloping side-rail guides of the gate where the surface has been machined down to something like 0.17 or 0.18 mm (0.15 mm film thickness plus room to move) higher than the inner rails upon which the film rests. The precision is in the camera gate, not the cartridge, which just needs the pressure pad area under the film and its extending tabs to be flat.

 

 

Edited April 29, 2013 by Dom Jaeger

[Erkan Umut]

I have searched some service manuals, and got these results:

 

Canon DS8 has these characteristics: Pressure plate pressure - 70-90gr, Side gate pressure - 40-60gr, Take-up torque - 60-90gr per cm (100ft), etc.

 

Canon Canonet 8 (D8): Pressure plate pressure - 40-60gr, Counter pressure - 20-25gr at the tip, Take-up torque - 40-60gr per cm (25ft), etc.

[Jean-Louis Seguin]

I was going to post this but then I read the thread again and saw that Dom had answered this already.

Well, anyway, here goes:

 

I do not have those figures but in the case of super8 cartridges it wouldn't make a difference anyway since the so-called "pressure plate" does not press at all! When the cartridge is in place, the plate aligns with the aperture gate to form a channel of fixed width that the film slides through. The gap is 0.20mm. Acetate film thickness is typically 0.14mm. The film is only held in place by the two side grippers in the gate. Without these grippers, the film slides through the gate with no resistance whatsoever.

 

Jean-Louis

Edited April 29, 2013 by Jean-Louis Seguin

[Andries Molenaar]

Then what is point of having lenses collimated to cameras when the position of the filmplane is not fixed? People split hairs over the effect of a gel filter and the filmplane cannot be bothered with?

 

And what does the Framemaster (Euro 120 chromed plate insert for S8 cartridges) do when it cannot press and fix the film in a defined plane?

[Andries Molenaar]

Please elaborate on how this Beaulieu SD8/60 does work. I see no interlocking plate.

 

There is no stoppage bender. And I doubt there is a speed regulator on the sprocketed hub in the middle. Does it work at all?

 

I don't have this thing. Images were save from webpages/auctions.

Edited April 30, 2013 by Andries Molenaar

[David Cunningham]

Then what is point of having lenses collimated to cameras when the position of the filmplane is not fixed? People split hairs over the effect of a gel filter and the filmplane cannot be bothered with?

 

And what does the Framemaster (Euro 120 chromed plate insert for S8 cartridges) do when it cannot press and fix the film in a defined plane?

 

Generally speaking a properly adjusted/serviced high-end Super 8 camera is going to keep the filmplane very close to if not actually fixed. It's all about those little film holding pins on the side of the gate. The backing on the cartridge helps to push the film into those clips where it is (hopefully) held steady.

 

The Framemaster helps the process along by actually engaging the clips as well and giving the Super 8 gate more rigidity (like a 16mm gate) so the film IS pushed on by the pressure plate to help hold it in place and help it to slide more smoothly through the gate.

[Jose luis villar]

The metal FrameMaster in my Beaulieu 4008 works well , but not in the Canon 1014 and 814 xls. Somewhere I read that did not work well on all cameras.

[Jean-Louis Seguin]

Even though there is some "slop" in the gate, the film's inherent curl keeps the emulsion pretty much always in the same plane. Except of course for the focus breathing effect at the 25th frame after each cut which is caused by a very tiny reversing roller inside the super8 cartridge. How noticeable this breathing will be depend on how long the film has been stationary and the f/stop you're shooting at.

 

Cheers,

Jean-Louis

Edited April 30, 2013 by Jean-Louis Seguin