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16mm registration test question


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Hey,

 

So i recently did a registration test on an SR3, and I got back some curious results.

 

For the test I shot

25' @ 24fps

25' @ 48fps

25' @ 75fps

 

then rewound and did the same thing again with the chart moved a bit.

 

I was expecting the 24fps to be rock solid, and the 48 and 75fps to have a little play, but it was the opposite. 75 was super solid, and 48 was a hair more wobbly, and 24 was loose.

 

is that normal?

 

and secondly, and i know this is hard to describe over text, but how steady should i be expecting a super 16mm to be? maybe it's a totally acceptable amount of wobble at 24fps and i am just expecting it to be better than it should be.

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Drew,

 

You should not have moved your shooting test chart "a bit" regarding your second exposure. Both exposures utilize identical setups relative to framing and distance from focus chart (x,y and z axis). The projected or scanned footage will reveal x,y,z axis movements indicating potential registration issues. Both the projector and the scan introduce small "registration" errors but can be neglected for your purpose.

 

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The chart can be self made, a checkerboard of vertical and horizontal lines. For the second exposure, just rotate the chart about one or two degrees. With the lines being at such an acute angle it's easy to see the intersection move if the regestration is off.

 

I was told that cameras with reg pins can show small, as if random instability. Cameras without pins can have larger, more rythmical instability. I did do this test on a 16BL and a CP-16, but it was ages ago and all I remember is how bad the CP looked.

 

I think a lot depends on the condition of the camera. If that needs work then having pins is no guarantee.

Edited by Gregg MacPherson
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As a rental tech I used to shoot steady tests on SRs every time one went out for a feature or long hire, must have shot dozens. I always twisted the chart (a grid) very slightly as Greg describes for the 2nd pass, makes it much easier to see any movement. I would also shoot the 2nd pass all at 24 fps, no need to shoot different speeds again. Also each mag got its own test, since SR mags are an integral part of the film transport and can affect steadiness. It's very important to have the camera firmly locked down to prevent vibration from appearing like camera unsteadiness. Make sure to only look for movement between the 2 exposures, not of the overall image.

 

A serviced SR3 should be rock steady at all speeds. I used to project the developed neg onto a 10 ft screen to check for movement, and usually couldn't see any. These days with everything getting scanned and corrected in post it might not be as big a deal as it used to be, I don't know I'm not a post guy.

 

It's possible for a camera to get steadier at higher speeds if the fault is say a particular wear in the movement which is masked by faster motion of the linkages, but usually yes steadiness is better at normal speeds.

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Dom, I must object. Vertical image steadiness with a register pin camera depends on two things.

 

One is the fit between pin and perforation. Arnold & Richter has a two tenths millimeter long taper on the pin. Let’s assume the pin is well set along its motion axis.

 

The other thing is the pin guide or pin mechanims bearing(s). There may be play.

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  • 2 weeks later...

Hey guys,

 

So I havent solved the mystery of the first test, but I spoke with Guy at Panavision hollywood and he gave me some insight and pointers:

 

He said that in his experience any unsteadiness on an SR could just as easily be a magazine issue as it could be a camera issue. He suggest I try all 3 mags and see if any mags seemed to be troublesome.

 

he also said that the way they do test over there is the following: Shoot the chart at 24, shoot it again at whatever the highest frame rate you'll be using is, then shift your chart and reshoot it all at 12 fps. he said that this 12fps pass solved a lot of issues for them.

 

So that what I did, and I got a pretty good results from all of my mags. Im guess the issue on the first one was just a fluke. Who knows.

 

Thanks!

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  • Sustaining Member

He said that in his experience any unsteadiness on an SR could just as easily be a magazine issue as it could be a camera issue. He suggest I try all 3 mags and see if any mags seemed to be troublesome.

This has been my experience. Thorough magazine testing is really important. When you have a good one baby it. Love it. Pet it from time to time.

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