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Registration test in reverse


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#1 Kar Wai Ng

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Posted 28 April 2007 - 12:13 AM

Is it okay to run the second pass of a reg test in reverse (on cameras that run reverse), or should you always rewind on a bench and run it forwards only on the camera? Is it possible for registration error to show up when running reverse but not forwards (or vice versa)? I figure that the movement isn't really doing anything different, just doing everything in the reverse order, but I wasn't sure about whether registration would be affected by the film direction...
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#2 Bernie O'Doherty

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Posted 28 April 2007 - 04:40 AM

Theoretically there should be no difference. In practice, however, there are things like claw and registration shape differences. Mag feed and take-up tensions working in reverse etc.
All that being said, I'd love to hear the result !
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#3 Stephen Williams

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Posted 28 April 2007 - 04:59 AM

Is it okay to run the second pass of a reg test in reverse (on cameras that run reverse), or should you always rewind on a bench and run it forwards only on the camera? Is it possible for registration error to show up when running reverse but not forwards (or vice versa)? I figure that the movement isn't really doing anything different, just doing everything in the reverse order, but I wasn't sure about whether registration would be affected by the film direction...


Hi,

With a camera such as a Mitchell with 2 register pins it makes no difference whatsoever, however unless you are shooting some passes forward & some passes backwards (which is comen with motion control), its not a useful test! Should the results not be steady, it does not help in establishing if the camera in question is steady when shooting forwards.

Stephen
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#4 Bernie O'Doherty

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Posted 28 April 2007 - 08:00 AM

Good point Stephen. Perhaps it would mean doing double image exposures forward as one test of forward stability. Then doing double image exposure tests separetely (different 100 ft roll) running in reverse.
At least one could test forward stability versus reverse stability.
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#5 Chris Keth

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Posted 28 April 2007 - 09:44 AM

It won't help you as a test very often but it saves you time if you run in reverse with a lenscap on then do the second run of your test.
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#6 Kar Wai Ng

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Posted 28 April 2007 - 11:45 AM

It won't help you as a test very often but it saves you time if you run in reverse with a lenscap on then do the second run of your test.



I've been very tempted to do that; basically using the reverse mode as a 'rewind' only thing. But then I've been told I shouldn't do that because it puts extra stress on the perfs and when you do your second forward pass, the film's already been through two passes which might affect the perf shape and hence stability on the second pass. Is there any truth to that?
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#7 Stephen Williams

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Posted 28 April 2007 - 12:00 PM

I've been very tempted to do that; basically using the reverse mode as a 'rewind' only thing. But then I've been told I shouldn't do that because it puts extra stress on the perfs and when you do your second forward pass, the film's already been through two passes which might affect the perf shape and hence stability on the second pass. Is there any truth to that?


Hi,

In the past I have exposed film with 100+ passes using Oxberry & Mitchell cameras, 16 + 35mm without problem. If the camera is 'picking' the perfs it's not a good sign, looking at the perfs with a magnifying glass will reveal any problems.

Stephen
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#8 Kar Wai Ng

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Posted 28 April 2007 - 08:03 PM

Sounds reassuring. I guess it's not something I should really worry about.

Thanks everyone for your input.
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#9 Chris Keth

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Posted 28 April 2007 - 08:07 PM

Sounds reassuring. I guess it's not something I should really worry about.

Thanks everyone for your input.


I wouldn't worry about it. Film is tough stuff. Think of how many times a release pring goes through the projector movement. Even by the end of its working life it's still steady. One more run through a camera won't hurt it.

The only thing I would avoid, if you're doing high-speed registration tests, is also running the film in reverse to rewind it at a high speed.

Edited by Chris Keth, 28 April 2007 - 08:08 PM.

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#10 Jon Kukla

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Posted 30 April 2007 - 02:32 AM

I wouldn't worry about it. Film is tough stuff. Think of how many times a release pring goes through the projector movement. Even by the end of its working life it's still steady. One more run through a camera won't hurt it.


That's not quite a fair comparison - film neg is BH perfs on acetate stock, while prints are KS perfs (bigger) on estar (stronger).
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