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Aaton XTR Prod Slight Jitter


Sean Dahlberg

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I recently received scans back and noticed this very slight jitter in some of the dailies, maybe. It's possible this is normal but I don't believe I've noticed this prior to this specific project, it almost looks like I'm slightly bumping the camera mid shot. I'm wondering if this is possibly due to the loop being a bit too tight when loaded? I did have a loader who was new to the XTR and was loading the mags slightly tighter than I usually do, she was allowing for about 13-13.5 frames where I usually loop a solid 14.  Any insight into this would be appreciated! 

https://vimeo.com/740033487/c1b06f3b50

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Hard to tell without looking at the perfs, it's not "bad" at all. It could be the scan as well. The quality of the Vimeo link is horrible, so it's even harder to tell. I'd upload at MUCH higher bandwidth. 

A bad loop would be evident by loudness or big jumps in the image. 

Loop needs to be 14 visible perfs if you pull the film from the throat. 

 

Edited by Tyler Purcell
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If you’re concerned about camera steadiness it’s very easy to shoot a quick double exposure steady test and rule out the camera.

Working at rental houses we used to steady test every camera before a production.

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If you happen to have a full aperture scan of your most recent footage, take a look at the relationship of the perfs to the frame and or the frames to each other.

If it looks like the space in between frames is varying or if the relationship between the location of the perf and the frame is varying then the registration is off. 

If the perfs and frames are both moving but their relationship is constant, it's the scanner. 

If time and money allow shoot a proper double exposed reg test. 

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I would get a overscan done so you can see the camera gate relative to the perforations.

If the perfs are not moving but the gate has this movement then it is in the camera or loading.

We do a 2.5K overscan on our Scan Station for camera tests it really helps to see the perfs.

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19 hours ago, Robert Houllahan said:

I would get a overscan done so you can see the camera gate relative to the perforations.

If the perfs are not moving but the gate has this movement then it is in the camera or loading.

We do a 2.5K overscan on our Scan Station for camera tests it really helps to see the perfs.

Hi Rob,

Most of the time an overscan would pick up camera unstability, but there is some room for error because 16mm cameras register the film laterally by the edge of the film rather than the perf. Only vertical registration is controlled by the perfs. In theory the edge of the film and the perf edges should be locked together but of course this depends on the perforation and film width QC and not all cameras use the film edge directly next to the exposed frame perf (so if there is any weave in the film itself it may show up as camera unsteadiness).

So I tend to recommend a double exposure steady test because it's the ultimate way to rule out any other factors, and you can test different speeds and each mag as well (important for 16mm cams that have the pressure plate in the mag). 

But I'm approaching this as a camera tech not a scanning expert, so perhaps I'm being overly cautious? I'm curious to hear your thoughts on using the edge of the perf for lateral registration when scanning 16mm. And how important is camera steadiness nowadays anyway? Are there downsides to post stabilisation? 

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20 hours ago, Dom Jaeger said:

Hi Rob,

Most of the time an overscan would pick up camera unstability, but there is some room for error because 16mm cameras register the film laterally by the edge of the film rather than the perf. Only vertical registration is controlled by the perfs. In theory the edge of the film and the perf edges should be locked together but of course this depends on the perforation and film width QC and not all cameras use the film edge directly next to the exposed frame perf (so if there is any weave in the film itself it may show up as camera unsteadiness).

So I tend to recommend a double exposure steady test because it's the ultimate way to rule out any other factors, and you can test different speeds and each mag as well (important for 16mm cams that have the pressure plate in the mag). 

But I'm approaching this as a camera tech not a scanning expert, so perhaps I'm being overly cautious? I'm curious to hear your thoughts on using the edge of the perf for lateral registration when scanning 16mm. And how important is camera steadiness nowadays anyway? Are there downsides to post stabilisation? 

All true, when we have had Pro jobs in that have been doing double exposure registration tests we do an overscan as well as that combination gives the most detail and feedback about the camera registration.

Just did one for an Arricam LT today which was double exposure and a 3K overscan 4-perf camera.

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The stabilization test can be pretty inconclusive tho, unless your camera is REALLY messed up. 

We do registration tests like this for every camera we do full re-build's on. This way we know if the timing is good as well. 

This particular camera I had to do a full re-build on, the movement had an issue. So this is the final test. 

The chart we use is a tube that projects it onto the camera aperture with a lens. You shoot it one way, then turn it around and shoot it another way after rewinding the film. Thus you two different set of lines. In this test, you'll see the lines match up perfectly, but the registration is still off. We did register this test via the perf, but we also tried registering it with the film edge, which was way worse. 

https://vimeo.com/586435368

Edited by Tyler Purcell
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On 8/19/2022 at 12:57 PM, Tyler Purcell said:

The stabilization test can be pretty inconclusive tho, unless your camera is REALLY messed up. 

No, a double exposure registration test is the most reliable way to check camera registration. It’s how camera manufacturers tested them, how rental houses tested them, how techs test them. 

I’ve shot dozens of steady tests and we could pick up if a camera had less than 10 microns of play between passes. 

If your camera exposed two seperate passes of a grid chart and the grids were locked together, then the camera registration is good. It has to be, since you can’t have unsteadiness that perfectly replicates itself on completely seperate passes. Play in the system always manifests as random movement over time.

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