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Kind of double-exposure at frameline with Eclair Cameflex 2-perf; is it normal?


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#1 Christos Dassios

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Posted 15 November 2017 - 07:49 AM

Dear community,

 

finally I got some results, showing the first test-shots with an Eclair Cameflex 2-perf.

I shot a shortend of b/w in magazine#1 and some color-stock in magazine#2.

After developing, the film was scanned in 4k (full-frame, perf to perf).

Both the shots show a kind of double-exposure instead of an accurate frameline.

Masking 2.39:1 is alright, although I don't know what is actually being cropped, of what has been shown on the ground-glass before (unfortunately, I did not shoot a frameleader).

But, masking 2.35:1 leaves a small "light bar" top and down, when centered vertical correctly and using the full width.

 

Question: Is this phenomenon normal for a 2-perf Cameflex, due to its transport mechanism? Or is there a need of adjustment? If yes, where an how? Magazine's pressure-plates?

 

By the way, the image is satisfying steady.

 

Thank you

Dassios

 

 

Attached Images

  • Testframe.jpg
  • 2.35.jpg
  • 2.39.jpg

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#2 Simon Wyss

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Posted 15 November 2017 - 09:08 AM

Simple enough, you compare aperture height to film step.

Film step or advancement length is theoretically half that of regular film (19 mm), alas 9,5 mm. If the aperture (mask) is higher or about the same, you don’t have any separation or frameline with negative stocks or positives respectively.


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#3 Samuel Berger

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Posted 15 November 2017 - 11:45 AM

The gate on some CM3s has these little divots on each side and top and bottom, I never understood why. I didn't expect the 2-perf version to have them as well but from your frames I can see there they are.

 

divots.jpg


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#4 Dom Jaeger

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Posted 15 November 2017 - 12:15 PM

The extracted or projected frame is always a little smaller than the full aperture exposure, if you had shot a frame line leader you would no doubt find that the ground glass frameline is well within those edges. As Simon said, the reason you have no gap between exposed frames is because the gate aperture is too tall, resulting in a small double exposure overlap - I would assume whoever did the conversion has made it so.

Those divots at the edges of the gate aperture are a form of camera signature, every camera model had a different pattern that could identify it from the negative.
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#5 Paul-Anthony

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Posted 15 November 2017 - 12:27 PM

I had the same problem.
The size of your 2 perf window is not correct. The conversion of your camera was probably done in England, lots of cameras converted in England had that little problem.

I had to do a new gate for the camera at Aranda in Australia.

The image once cropping the double exposed area is more or less a 2.50 ratio.

Here was my problem, the same : IMG-20160831-WA0004.jpg.0d3165b6754af17b


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#6 Christos Dassios

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Posted 16 November 2017 - 07:01 AM

Wow, a lot of quick and competent responses, what an impressive board! Thank you.

Simon, I measured the gate and it is somewhat less than 9,5mm and more than 9,4mm in height. From a formerly shot - with an Arricam LT 2-perf - I know, there is no frameline in itself, but the images were joining accurately.

Samuel and Dom, interesting information about those divots. I thought, they are needed to specify the exact frame's center vertical and horizontal.

Paul-Anthony, you are right. I bought this camera in England and it is believed, that it was used by the BBC once, as along with it there came two AC 25fps motors. The modification could have been done by Alex Georgiou, maybe.

The height of an exposed frame on the negative is definitively larger than of the gate. About 9,5-9,6mm including the double-exposure.

I suppose, the double-exposure derives from the fact, that the 2-perf mask is not "leveled" with the original gate. There are missing about 0,6mm to cover the negative flat. Maybe some kind of flaring?

Nonetheless, I have to do a test-shot with a frame leader. If the image seen on the ground glass will be within the usable image, I will no longer care about this double-exposure and regard this as a characteristic like the triangular divots.

Thanks a lot again and regards to Basel, Seattle, Melbourne and Paris.

Dassios


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#7 Mark Dunn

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Posted 16 November 2017 - 07:29 AM


Samuel and Dom, interesting information about those divots. I thought, they are needed to specify the exact frame's center vertical and horizontal.

I was also wondering if they were fiducials for photogrammetry. You often see them on NASA instrumentation films, but they protrude into the frame, not the rebate.


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