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A Few Questions about Arri SR3 Film Gate


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#1 David Fitch

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Posted 19 January 2014 - 12:10 AM

I was wondering if someone might be able to help with a few SR3 questions specifically related to the film gate.  In looking at some SR3 images I've found online, I noticed that in many of the pictures, there is what appears to be a small screw mounted a few millimeters above the center of the gate.  Some of the documentation I've found has described this as an adjustment screw for viewing screen height / frameline position.  Was this adjustment screw present on new SR3s from the factory, or is it usually only found on modified or overhauled gates or cameras?  The reason I ask is that this seems like the last place you would want to mount a screw, given its proximity to the film path.  I'm guessing that the screw must be flush mounted or recessed, but it seems that even a microscopic burr on the screw head could potentially scratch the emulsion and be disastrous.  Is this a valid concern, or are there safeguards in place to prevent film scratches?

 

Secondly, I've read about some SR3 gates "without top or bottom rails on the gate".  Can someone explain what this means, and if it's a feature on all SR3s or only on upgraded or overhauled cameras?

 

Thanks to anyone who can help! 


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#2 Dom Jaeger

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Posted 19 January 2014 - 08:56 PM

Hi David,

the set screw above the gate aperture is an adjustable stop for the ground glass which sits just behind, to set the viewing frame height. It should really only be adjusted by a trained technician, who would never introduce burrs to the screw! But it is recessed and lacquered in, and the screw hole itself is at a level well under the film support rails, so there's really no chance it will damage film. I've seen this on Standard and Super gates, so it goes back to SR2 at least. Can't actually recall any SR gates that don't have it, but it's been a long time since I saw an SR1.

 

Your second question I'm guessing relates to the new gate design that came in with the SR3 Advanced in 1999, where the old design with fixed top and bottom side rail blocks was replaced with two continuous side rails with sprung saphire rollers on the non-claw side. It solved the problem of wear to the side rails which could eventually cause lateral unsteadiness.

 

Newer gate on left:

SR gates.jpg

 

 


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#3 David Fitch

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Posted 20 January 2014 - 09:12 PM

Dom,

 

Thanks for the information about the screw above the gate aperture.  As for my question about rails at the top and bottom of the gate, I think I've figured out that question.   In both photos you posted, note that above and below the gate opening there are two (silver colored) horizontal rails - one right above the opening and one below.  Compare that to the image I found online and have posted below.  Note that there are no horizontal rails at the top and bottom of the gate opening.

 

From what I've read, this modified gate design with no top and bottom rails at the gate opening is supposed to decrease the chances of dust or a stray hair getting caught in the gate.  Can anyone else verify the purpose of this particular type of gate design, and/or pros and cons of this design versus the original factory gate design with the horizontal rails?

 

S16gate.jpg


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#4 Tim Carroll

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Posted 27 January 2014 - 10:29 AM

Never actually saw one of those gates in person when I used to service the SR line of cameras.  In theory I can understand the concept, but I would be more concerned that with the gate pictured above you would not get a clean frame line on the top and bottom of each image, possibly causing bleed between the images on your strip of film.


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