Jump to content


Photo

Arri Sr2 "moving gate" problem


  • Please log in to reply
26 replies to this topic

#1 Kalle Folke

Kalle Folke
  • Basic Members
  • PipPip
  • 77 posts
  • Other
  • Stockholm

Posted 28 March 2014 - 12:18 PM

Hi!

I'm happy owner of a used Arri Sr2. I come from the "video world" and shooting film has been a life long dream to me. I'm very great full for this forum and have had a lot of help from it.

After doing my first tests I have a million questions… It would be a bit too overwhelming to write everything now, so I'll start with my main concern.

 

See this:

https://vimeo.com/90344273

 

I've uploaded a test on Vimeo, I'm not sure what the english word is (in Swedish I think it's bildstilleståndstest- a unique word with no match on google, haha). In the video you'll see that the whole gate is moving a bit, but the lines that are double exposed seems to move consistently. From what I've understood this should mean that the camera produces a stable image. Why then is the whole frame moving? Is this a problem with scanning?

 

On my Vimeo: http://vimeo.com/folkefolke I've also uploaded more from my first test with Kodak 7219. Any feedback would be appreciated, and I'm sure I'll keep the post's with questions coming...

 

Hope I managed to make sense even if I'm lacking the technical terms in english.

 

Thank you/Kalle


  • 0

#2 Freya Black

Freya Black
  • Basic Members
  • PipPipPipPip
  • 4161 posts
  • Other
  • Went over the edge... Central Europe

Posted 28 March 2014 - 01:45 PM

I think you might be talking about "Gate Weave" but I don't see much evidence of this. Your footage looks mostly stable.

You can see the perfs on the left hand side and they move very little.

 

I'm thus not sure what you mean.

 

Freya


Edited by Freya Black, 28 March 2014 - 01:46 PM.

  • 0

#3 Mark Dunn

Mark Dunn
  • Basic Members
  • PipPipPipPip
  • 2424 posts
  • Other
  • London

Posted 28 March 2014 - 01:50 PM

bildstilleståndstest

Picture steadiness.

 


  • 0

#4 Kalle Folke

Kalle Folke
  • Basic Members
  • PipPip
  • 77 posts
  • Other
  • Stockholm

Posted 28 March 2014 - 02:27 PM

I think you might be talking about "Gate Weave" but I don't see much evidence of this. Your footage looks mostly stable.

You can see the perfs on the left hand side and they move very little.

 

I'm thus not sure what you mean.

 

Freya

 

Thanks for your reply. What is "Gate Weave"?

 

Even if the perfs look stable the whole frame is moving. You also see it clearly in this video after 03.25: https://vimeo.com/89728141

That test shot is on a locked off tripod but the frame is still moving. I mostly shot my test handheld and then it's not as noticeable.

The first picture steadiness test is shoot on an expired Kodak 7207 250D and everything else on a fresh Kodak 7219 500T, so it shouldn't be a problem caused by the film.

 

Looking forward to hear any thoughts.


  • 0

#5 Kalle Folke

Kalle Folke
  • Basic Members
  • PipPip
  • 77 posts
  • Other
  • Stockholm

Posted 28 March 2014 - 02:44 PM

Hi again, 

Did some quick research on gate weave and could it be that this is a general problem with all Sr's before the Sr3 Advanced with it's improved gate?

If this is considered "normal" I guess I'll have to shoot hand held all the time...


  • 0

#6 Dom Jaeger

Dom Jaeger
  • Basic Members
  • PipPipPipPip
  • 1602 posts
  • Other
  • Melbourne, Australia

Posted 28 March 2014 - 06:15 PM

Hi Kalle,

congratulations on your new camera.

 

The technical term in English would be "steady test" or "registration test". Your camera looks to be rock solid. You only need to look for movement between the 2 grids, and your test shows none at all. Any movement of the whole picture is due to something external to your camera, like the transfer. 

 

SR1s and 2s don't really have a problem with gate weave normally, they just have fixed side rails in the gate which after a lot of film has passed through can wear a groove that allows some lateral movement. Once detected it's easily fixed with new rails or another gate. The SR3 Advanced gate uses saphire spring-guides which never wear.


  • 0

#7 David Cunningham

David Cunningham
  • Basic Members
  • PipPipPipPip
  • 1049 posts
  • Cinematographer

Posted 28 March 2014 - 10:02 PM

I agree with Dom on the lateral movement part.  The "registration" is nearly perfect.  But the film does seem to weave back and forth just a hair.  

 

The reason the double exposure test footage looks solid may be that the perfs are not perfectly solid on the film itself thus causing the film to move just a hair and the slightly warn gate allowing for that lateral movement.  I have seen lateral movement caused by lateral movement in the perforations before.  The pitch can be perfectly registered on the film (so no vertical movement or variation in space between frames), but the location of the perforations relative to the edge of the film may be weaving slightly and the not particularly tight gate allowing for it.

 

That's my take anyhow.


  • 0

#8 Kalle Folke

Kalle Folke
  • Basic Members
  • PipPip
  • 77 posts
  • Other
  • Stockholm

Posted 29 March 2014 - 08:13 AM

Thank you both for you input, makes total sense. I can't really see any groove on the rails/gate, but I guess it could still be worn. I don't know any detailed history about the camera except that it's been used by a German tv-network. So even if the Super16 gate can't be very old there's probably been a good amount of film passing the gate.

 

My guess is that changing to a unused gate (a Sr3 Advanced gate would be best maybe?) would be more expensive than what I payed for the camera (1800€ for complete kit). Is this correct, or do you know about any good places to look, preferably in Europe? I'd love to find a service tech in Sweden...

 

A lot of things to learn, but also very exiting. Thanks again!


  • 0

#9 Dom Jaeger

Dom Jaeger
  • Basic Members
  • PipPipPipPip
  • 1602 posts
  • Other
  • Melbourne, Australia

Posted 29 March 2014 - 08:57 AM

  The reason the double exposure test footage looks solid may be that the perfs are not perfectly solid on the film itself thus causing the film to move just a hair and the slightly warn gate allowing for that lateral movement..

 

Hi David, 

the gate isn't worn, the camera registration is good.  The important thing is that the grids are locked together, which means that on separate passes the image is not moving. If there was any play in the registration the two grids would be moving independently, quite obvious when you see it.

 

Lateral registration in SRs (or any 16mm camera or projector really) is controlled by the film edge not the perfs, the registration pin only secures the vertical position, it doesn't fill the perf width. Slight variations in the lateral position of a particular stock's perforations won't affect a camera's registration, but it could affect the steadiness of a scan if only the perf is used as an anchor. 

 

I'm not really up with developments in scanning software, but aren't there pretty good stabilisation programs these days anyway?


  • 0

#10 David Cunningham

David Cunningham
  • Basic Members
  • PipPipPipPip
  • 1049 posts
  • Cinematographer

Posted 29 March 2014 - 04:14 PM

There are very good stabilization functions even just built into Adobe after effects and apple motion.

But, in the case of this footage, the perfs appear to stay rock solid but the frame sways side to side. That tells me the film is swaying back and forth in the gate. Ya probably happening evenly and equally in each pass because the gate is edge guided.
  • 0

#11 Brian Drysdale

Brian Drysdale
  • Basic Members
  • PipPipPipPip
  • 5070 posts
  • Cinematographer

Posted 29 March 2014 - 06:48 PM

I'd try getting your film transfered at another facility to check if it's the transfer,


  • 0

#12 David Cunningham

David Cunningham
  • Basic Members
  • PipPipPipPip
  • 1049 posts
  • Cinematographer

Posted 29 March 2014 - 09:36 PM

You can definitely try another transfer to confirm.  But, if you review the footage, you can see that the perfs stay perfectly registered and the frame moves laterally.  It does so perfectly for both exposures.  So, it sounds to me like the edges of the film itself were non-uniform and following the edges of the gate.

 

This is a natural and expected result of "edge guided" lateral centering.  There's nothing much that can be done about it.

 

If you shoot in a locked position on a tripod, and the movement is noticeable, you will be able to "fix" it with motion stability software.  You likely will not get a different result with a different camera.

 

This scan was probably done using a perforation only centering mechanism (in a computer).  You would likely not see this problem as badly on an edge-guided setup such as a Spirit.


  • 0

#13 Kalle Folke

Kalle Folke
  • Basic Members
  • PipPip
  • 77 posts
  • Other
  • Stockholm

Posted 30 March 2014 - 03:41 PM

I'd try getting your film transfered at another facility to check if it's the transfer,

 

Well, problem is it's the only lab in Scandinavia still running so not sure where to send it… Also now when it's more of a personal development project I can't spend too much money on it. But will keep it in mind if I can't live with the issue.

 

You can definitely try another transfer to confirm.  But, if you review the footage, you can see that the perfs stay perfectly registered and the frame moves laterally.  It does so perfectly for both exposures.  So, it sounds to me like the edges of the film itself were non-uniform and following the edges of the gate.

 

This is a natural and expected result of "edge guided" lateral centering.  There's nothing much that can be done about it.

 

If you shoot in a locked position on a tripod, and the movement is noticeable, you will be able to "fix" it with motion stability software.  You likely will not get a different result with a different camera.

 

This scan was probably done using a perforation only centering mechanism (in a computer).  You would likely not see this problem as badly on an edge-guided setup such as a Spirit.

 

So just to make sure I understand correctly: This would still be an issue even if I change the gate/camera? I think the lab has a Scanity (can double check this…).

 

Thanks for all your help, it's a lot to take in and I appreciate that you're all so generous with your time and knowledge.

 

Will continue to do tests, but at the same time try to start getting some footage that useful for a personal project I'm planning to do. Let's hope I'll find a way to work around the "moving" or that it won't be a mayor issue in most footage.


  • 0

#14 Chris Millar

Chris Millar
  • Basic Members
  • PipPipPipPip
  • 1642 posts
  • Other

Posted 30 March 2014 - 07:38 PM

 

Well, problem is it's the only lab in Scandinavia still running so not sure where to send it… 

 

Back to them, with the vimeo link - kindly ask them to join in the discussion.

 

Or ...  much less fuss - be happy, the weave is so minimal that any post correction (if required) will leave next to zero artefacts.


  • 0

#15 David Cunningham

David Cunningham
  • Basic Members
  • PipPipPipPip
  • 1049 posts
  • Cinematographer

Posted 30 March 2014 - 10:01 PM

 

 

So just to make sure I understand correctly: This would still be an issue even if I change the gate/camera? I think the lab has a Scanity (can double check this…).

 

 

 

If the problem is that the edge of the film is "wavey", then correct... you would not be able to change this with any other camera or repair to this one.

 

However, I do not know enough about this camera to be sure of anything except that the film was definitely moving laterally back and forth in the camera.  I can't be 100% sure why.  But, again, I'm sure it's not the scan causing your problem.  The perforations stay rock solid in the scan, but the frame still moves side to side.  So, the frame actually moves side to side on the film for some reason and since it didn't break your test, clearly it's perfectly consistent lateral movement.


  • 0

#16 Brian Drysdale

Brian Drysdale
  • Basic Members
  • PipPipPipPip
  • 5070 posts
  • Cinematographer

Posted 31 March 2014 - 01:56 AM

I think it's worth noting this thread: and what Jeff Kreines says about SRs.

 

http://tig.colorist....on_for_Scanning


Edited by Brian Drysdale, 31 March 2014 - 01:57 AM.

  • 1

#17 Gregg MacPherson

Gregg MacPherson
  • Basic Members
  • PipPipPipPip
  • 1883 posts
  • Other
  • New Zealand

Posted 31 March 2014 - 03:45 AM

So which SRs had or didn't have side pressure bars at the gate?  ACLs and Aatons had them (on the claw,  perf side),  but then they didn't have reg pins.


  • 0

#18 Brian Drysdale

Brian Drysdale
  • Basic Members
  • PipPipPipPip
  • 5070 posts
  • Cinematographer

Posted 31 March 2014 - 04:20 AM

I gather it's the SR3 model which had them fitted . Dom goes into some detail on the subject: http://www.cinematog...p?showtopic=621

 

From memory the registration pin on the SR isn't fully fitting as found on 35mm film cameras like the Mitchell.


Edited by Brian Drysdale, 31 March 2014 - 04:24 AM.

  • 0

#19 Freya Black

Freya Black
  • Basic Members
  • PipPipPipPip
  • 4161 posts
  • Other
  • Went over the edge... Central Europe

Posted 31 March 2014 - 04:56 AM

 

Thanks for your reply. What is "Gate Weave"?

 

Even if the perfs look stable the whole frame is moving. You also see it clearly in this video after 03.25: https://vimeo.com/89728141

 

That looks much more severe and you can see the perfs moving a lot in that footage, even on the handheld stuff.

 

Freya


  • 0

#20 David Cunningham

David Cunningham
  • Basic Members
  • PipPipPipPip
  • 1049 posts
  • Cinematographer

Posted 31 March 2014 - 12:57 PM

 

That looks much more severe and you can see the perfs moving a lot in that footage, even on the handheld stuff.

 

Freya

 

The perfs do seem to move a bit on that footage as 3:25.  However, the frame relative to those perfs is the majority of the movement.  I think the channel the film runs through on this SR3's gate is just a bit too wide so the film is kinda swaying back and forth in it.


  • 0


Technodolly

Rig Wheels Passport

Glidecam

Paralinx LLC

Gamma Ray Digital Inc

Media Blackout - Custom Cables and AKS

Wooden Camera

rebotnix Technologies

CineTape

Aerial Filmworks

Ritter Battery

Willys Widgets

CineLab

Visual Products

Broadcast Solutions Inc

Tai Audio

Abel Cine

Opal

The Slider

FJS International, LLC

Metropolis Post

Willys Widgets

Gamma Ray Digital Inc

FJS International, LLC

Broadcast Solutions Inc

Visual Products

Ritter Battery

The Slider

Paralinx LLC

rebotnix Technologies

Abel Cine

CineLab

Wooden Camera

Technodolly

Tai Audio

Rig Wheels Passport

Glidecam

CineTape

Aerial Filmworks

Opal

Metropolis Post

Media Blackout - Custom Cables and AKS