35mm Motion Picture Film Cameras questions

[Ivan Ciarlantini]

Good morning Gents

 

as already mentioned before, i am not involved in the cinema industry and i would like to gather some technical info on Motion Picture Film Cameras.

 

First thing first: are there books or documents related to this topic? I managed to find a couple of patents on Free Patents Online, you can guess the basic cinematic chain of a camera movement but it is not as detailed and explaining. For other sources, i didn't know which books to look for.

 

Regarding the first technical on of the features i am curious about:

-The basic cinematic chain of a modern motion picture film camera

It concerns the transport of the film through the camera itself. I understand that it has to be a balanced mechanism in which all the Sprockets, The movement and the Magazine Spools contribute to the successful operation. In which way though? Which one of these components is primarily responsible for the film movement? Is it the movement itself? Or the sprockets? About the film magazines, i know arri and panavision installed electronics controlled motors in the magazines, in order to control film tension. How will they behave during operation? How was this achieved before installing those controls on the camera mag?

 

I think it is enough for now, i have plenty questions i will keep for later.

 

Thank you.

 

P.S.: No info or picture could be found regarding 70mm cameras (movements, ecc.), i am currently relying only on the user manuals, which are really really interesting (Arriflex 235, 435, 765

[Michael Rodin]

Excuse my terminology, I learned it all in Russian...

 

Constant-speed transport of film is done by a pair of drums which engage the perfs and reside on feed and take-up sides of the movement. In some cameras (pre-XL Panaflex, Soviet "Rodina") there's one drum - it's upper part engages film on feed and lower part on take up. There are rollers which press the film against the drum(s) and guide rollers. The constant-speed part must be gentle with film (low stress on perfs, reasonable bend radiuses) and, of course maintain precise speed (which it does as long as the motor does because it's linked to claw movement).

Then there's claw movement which's responsible for intermittent motion. It's linked to the shutter and advances the film while the shutter is closed. When it opens, registration pin(s) are go into perfs to hold film steady in the gate. There's still a large number of non-registered cameras in use though. Between movement and drum(s) loops of film are formed which are critical for maintaining constant feed/take up speed while the film travels intermittently in the gate. Were it not for loops, the whole mass of film would need to travel intermittently and experience huge accelerations (that would mean stress on film and motors in kilowatt range).

Feed and takeup shafts in a magazine are mechanically coupled to camera motor on most cameras. But because film reel diameter constanlty changes while the camera is running you can't hard-coulple it to the motor and drive it directly with constant speed. So they run the mag with the nominal speed and let the reels slip with friction couplings (фрикционы), keeping torque constant. Cameras like Moviecam and Panaflex have separate mag motors with a "soft" torque characteristic - they give more torque and get slower when load increases, eliminating friction couplings and the whole mass of mechanics that comes with them, making the camera quiter and gentler on film.

[Mark Dunn]

It's worth mentioning the Arriflex design philosophy which has drive sprockets in the mags and none at all in the camera, just a huge pre-formed loop.

Edited July 5, 2017 by Mark Dunn

[Ivan Ciarlantini]

Excuse my terminology, I learned it all in Russian...

 

Constant-speed transport of film is done by a pair of drums which engage the perfs and reside on feed and take-up sides of the movement. In some cameras (pre-XL Panaflex, Soviet "Rodina") there's one drum - it's upper part engages film on feed and lower part on take up. There are rollers which press the film against the drum(s) and guide rollers. The constant-speed part must be gentle with film (low stress on perfs, reasonable bend radiuses) and, of course maintain precise speed (which it does as long as the motor does because it's linked to claw movement).

Then there's claw movement which's responsible for intermittent motion. It's linked to the shutter and advances the film while the shutter is closed. When it opens, registration pin(s) are go into perfs to hold film steady in the gate. There's still a large number of non-registered cameras in use though. Between movement and drum(s) loops of film are formed which are critical for maintaining constant feed/take up speed while the film travels intermittently in the gate. Were it not for loops, the whole mass of film would need to travel intermittently and experience huge accelerations (that would mean stress on film and motors in kilowatt range).

Feed and takeup shafts in a magazine are mechanically coupled to camera motor on most cameras. But because film reel diameter constanlty changes while the camera is running you can't hard-coulple it to the motor and drive it directly with constant speed. So they run the mag with the nominal speed and let the reels slip with friction couplings (фрикционы), keeping torque constant. Cameras like Moviecam and Panaflex have separate mag motors with a "soft" torque characteristic - they give more torque and get slower when load increases, eliminating friction couplings and the whole mass of mechanics that comes with them, making the camera quiter and gentler on film.

Thank you so much for the magnificent explanation! I understand now why we need the loops in the camera and i actually never thought that inside the camera occurs a combination of constant and intermittent motion (all this is extremely fascinating). That explains why some camera systems require a certain LOOP LENGTH when changing mag, you need that length in order to allow to the film itself to form those two essential loops. I could already understand the use of the Feed and Take Up sprockets, which are as we said, responsible for the constant motion of the film. Regarding the motors: I suppose you have two main motors (temporarily excluding the magazine motors), i'm talking about the shutter motor and the movement motor. Am i right? Does the movement motor drive the claws and the feed/take up sprockets at the same time? How are claws (and the related motor) synchronized with the mirror shutter (and related motor)? Basically, do both motors constantly run and the synchronization is just correctly positioning the shutter when running the camera (and there you will be sure that the claws will move the film only when the shutter closes the gate). Am i misunderstanding something?

 

Another question regarding the mag: I can understand having an electric motor driving the take up reel since u need a calibrated winding speed and that requires a DC motor coupled with the reel by mean of a friction coupling (it would be really appreciated if any of you could link or post any source regarding this kind of frictions or clutches). Should i guess the motor in the feed reel is just for.. feeding film? The friction will just immediately stop the reel if the operator stops the camera (i was thinking that if you stop the camera when the feed reel is still full, the moment of inertia given from the reel weight could keep the reel turning).

Last: No books or sources to suggest?

 

Thank you for your time and patience :)

[Mark Dunn]

There's usually a single motor driving the movement and the shutter, synchronised through a gear train. The feed side is usually pulled off the reel by the mag or camera sprocket. It's not driven.

The slipping clutch on the takeup side can be as simple as a leather strap as it is on the Arri 2C. There's a teardown of a 2C on Dom's cinetinker blog.

Edited July 5, 2017 by Mark Dunn

[Michael Rodin]

Yes, my fault, feed shaft sits on another friction clutch, not coupled to motor. I can post a tech drawing of a Konvas friction clutch.

[Ivan Ciarlantini]

There's usually a single motor driving the movement and the shutter, synchronised through a gear train. The feed side is usually pulled off the reel by the mag or camera sprocket. It's not driven.

The slipping clutch on the takeup side can be as simple as a leather strap as it is on the Arri 2C. There's a teardown of a 2C on Dom's cinetinker blog.

Thank you mark for answering! Your answer is really interesting, i think you could imagine why i was so confused regarding this point. I couldn't understand why the feed reel should be driven, for which reason. Turns out it is not driven. :rolleyes: I'm starting to understand, really. I have to thank both of you guys. Interesting the link between camera movement and shutter, i thought they were driven by two different motors (which, if i think about it, makes no sense).

 

Thanks Again!

 

P.S. I needed to edit this post in order to thank you one more time for quoting the 2C teardown. I just checked the blog and it is really well explained, plus i could see the drive chain in detail.

Edited July 5, 2017 by Ivan Ciarlantini

[Ivan Ciarlantini]

Yes, my fault, feed shaft sits on another friction clutch, not coupled to motor. I can post a tech drawing of a Konvas friction clutch.

Yes mike, it would be really appreciated if you could post (for public knowledge) or send me via Private Message that drawing (or all sorts of drawings you have related to these Cameras). I would be really grateful ;)

[Tyler Purcell]

Cameras work very much the same as 8mm/16mm film projectors. The sprockets control the amount of film in the movement area and the pull down claw controls when the film moves through the gate. The shutter really only controls when the light hits the frame. So if you've ever run an old school film projector like my 16mm Kodak Pageant, that is pretty much how a camera works.

 

The big differences between a camera and a projector is that projectors break the light more then once per frame, where camera's don't. This is to help reduce flicker, where cameras shutters only break the light once per frame. Cameras also need to be smaller then projectors, so the movement needs to be made in a compact way, which is why they look totally different then projectors. The first 35mm Bolex camera was also a projector by the way.

 

Outside of the movement, the magazines are usually use a clutch assembly for takeup. I assume this is so the speed of the motor doesn't have to be perfect, as a direct drive system could easily snap the film.

 

Now... with that said, some cameras have sprockets in the magazines, some cameras have ONE sprocket that you load upper and lower. So there are different designs for sure. The American Cinematographer bible has most of the cameras thread patterns in the back, which is a cool reference.

 

One of the biggest differences between 16 and 35 cameras is the quick-load coaxial magazine design. With 16mm, most of the modern cameras are threaded in the magazine and all you do is push the magazine onto the back of the camera body and keep shooting. This keeps the down time to a minimal on set between re-loads. Most 35mm cameras need to be loaded and most importantly cleaned between each roll of film. There are a FEW quick-load 35mm cameras, the Aaton 35III is what I own and it works just like a 16mm camera, only a bit more clunky and shorter loads of course. So for most 35mm shows, the down time between loads can be up to a few minutes, which maybe OK for some shoots, but for others, it's nice to throw a mag on and keep shooting.

 

If you need/want pictures of the cameras, let me know cuz I got lots of video and pictures of movements in motion. :)

[Gregg MacPherson]

Just extending what Mark Dunn said,

The latest 35mm film camera designs shifted to separate motors for the intermittent movement, shutter, magazine. The specs for the Aaton Penelope and the Arricams seem to describe just that. I heard that Arricam was founded on the Movicam, so I wondered if Arri's separate motors idea started there, but I couldn't find anything...

 

I can sense why camera designers trusted mechanical relationships between movement, shutter and magazine for so long....it can be so dependable and tough compared to electronics...then something changed...There's probably a couple of chaps on the forum who might have an interesting opinion about what happened there...

[Simon Wyss]

Simple, noise suppression. Less gears, less noise, and torque distributed to several motors. The 765 takes less time to run up to speed thanks to a motor dedicated only to that.

[Ivan Ciarlantini]

Cameras work very much the same as 8mm/16mm film projectors. The sprockets control the amount of film in the movement area and the pull down claw controls when the film moves through the gate. The shutter really only controls when the light hits the frame. So if you've ever run an old school film projector like my 16mm Kodak Pageant, that is pretty much how a camera works.

 

The big differences between a camera and a projector is that projectors break the light more then once per frame, where camera's don't. This is to help reduce flicker, where cameras shutters only break the light once per frame. Cameras also need to be smaller then projectors, so the movement needs to be made in a compact way, which is why they look totally different then projectors. The first 35mm Bolex camera was also a projector by the way.

 

Outside of the movement, the magazines are usually use a clutch assembly for takeup. I assume this is so the speed of the motor doesn't have to be perfect, as a direct drive system could easily snap the film.

 

Now... with that said, some cameras have sprockets in the magazines, some cameras have ONE sprocket that you load upper and lower. So there are different designs for sure. The American Cinematographer bible has most of the cameras thread patterns in the back, which is a cool reference.

 

One of the biggest differences between 16 and 35 cameras is the quick-load coaxial magazine design. With 16mm, most of the modern cameras are threaded in the magazine and all you do is push the magazine onto the back of the camera body and keep shooting. This keeps the down time to a minimal on set between re-loads. Most 35mm cameras need to be loaded and most importantly cleaned between each roll of film. There are a FEW quick-load 35mm cameras, the Aaton 35III is what I own and it works just like a 16mm camera, only a bit more clunky and shorter loads of course. So for most 35mm shows, the down time between loads can be up to a few minutes, which maybe OK for some shoots, but for others, it's nice to throw a mag on and keep shooting.

 

If you need/want pictures of the cameras, let me know cuz I got lots of video and pictures of movements in motion. :)

Yes Tyler, i am desperately looking for pictures and videos, if you could be so kind to share them ^_^ Technical drawings are more than welcome, although i cannot find them, do i have to suppose they are not released at all?

Edited July 6, 2017 by Ivan Ciarlantini

[Gregg MacPherson]

Simon, do you think that the designers all saw these opportunities and that's it, or is there something about evolving electronics, their evolving ability to apply that technology or our readyness to accept it....something like that...

[Michael Rodin]

Konvas feed side friction clutch.

 

EDIT: f-ing forum software doesn't accept any image format, will sort out later

Edited July 6, 2017 by Michael Rodin

[Ivan Ciarlantini]

Konvas feed side friction clutch.

 

EDIT: f-ing forum software doesn't accept any image format, will sort out later

Michael may i suggest to you to use an online image uploader (e.g. Imageshack) or, if you have lots of data and pictures like Mr. Tyler Purcell, a dropbox (or any sort of temporary cloud service) would be more indicated.

Edited July 6, 2017 by Ivan Ciarlantini

[Tyler Purcell]

Yes Tyler, i am desperately looking for pictures and videos, if you could be so kind to share them ^_^ Technical drawings are more than welcome, although i cannot find them, do i have to suppose they are not released at all?

Hard to find technical drawings... I've never seen any outside of service manuals and many are very cryptic. Is there anything specifically you're wanting this info for? Because I have thousands of stills and dozens of videos, so I can probably get the exact piece your looking for.

[Dom Jaeger]

If you make friends with an established rental house that has or had a film camera inventory they will likely have a stash of old service manuals and technical drawings. You might even be allowed to pull a camera out and have a look at it.

 

A quick selection of drawings I found in some old service folders here at Panavision, including a IIC mag showing the slip clutches for take-up (reversible mags have clutches on both spindles):

 

 

 

[Ivan Ciarlantini]

Hard to find technical drawings... I've never seen any outside of service manuals and many are very cryptic. Is there anything specifically you're wanting this info for? Because I have thousands of stills and dozens of videos, so I can probably get the exact piece your looking for.

 

Tyler, anything related to camera movements and magazines, magazine ancillaries of "modern" motion picture film cameras. Let's say from the Arriflex 35 III until now passing for the arri line, moviecams, panavisions, aaton if you have any. If you also have material on 65mm film gauge movements and systems it would be appreciated, since i could only find a good amount of data in the American Cinematographer Manual (i managed to find the 7th edition). Plus anything showing the above mentioned drive train responsible for moving the movement and the shutter as well (pretty like the link Mark Dunn suggested regarding the 2C, which explained me a lot).

 

 

If you make friends with an established rental house that has or had a film camera inventory they will likely have a stash of old service manuals and technical drawings. You might even be allowed to pull a camera out and have a look at it.

 

A quick selection of drawings I found in some old service folders here at Panavision, including a IIC mag showing the slip clutches for take-up (reversible mags have clutches on both spindles):

 

 

 

Very nice drawings! Those are what i need, exploded views and cross sections. I found something in FreePatentsOnline typing "Panavision" in the search bar, and i have to say panavision registered a good and interesting amount of patents throughout the years.

[Michael Rodin]

Sorry for it taking so long...

Konvas slip clutch

[Ivan Ciarlantini]

Thank you for your contribution! Evwn though it is cyrillic i have a russian friend, i will try to translate it. Thank you so much!