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Shutter speed of non reflex Bolex?


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#1 Patrick Cooper

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Posted 10 April 2007 - 08:00 AM

From scanning information which is widely available, I know that the shutter speed of a Bolex H16 Reflex is approximately 66th sec when running at 24fps. However, information regarding shutter angles and speeds of non reflex Bolex H16 cameras are harder to track down. Would the shutter speed of a Bolex non reflex be 48th sec like the majority of 16mm cameras? Additionally, what would be the shutter speed of a Bolex non reflex be when used in single frame mode?
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#2 Michael Tisdale

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Posted 10 April 2007 - 03:13 PM

For a non-reflex H16, it depends on the age of the camera... The shutter angle was changed at the same time as double claw registration was introduced around 1954 (Serial number 100401 onwards.)

If it was made before serial number 100401, the H16 has a 190 degree aperture shutter.
If it has a serial number higher than 100401, the non-reflex H16 has a 144 degree shutter. From there you can just do the math for the FPS... Exposure Time = (fps x 360) / (Shutter AngleĀ°)

You can also find info on shutter angles for H8 and H16 cameras on my website.

For exposure times with single frame filming (on non-reflex H16 cameras), when the I-T lever is switched to Instantaneous :
< SN 100401 (190 shutter) -- 1/20sec when the speed dial is set to 8fps; 1/25sec at other speeds.
> SN 100401 (144 shutter) -- 1/25sec when the speed dial is set to 8fps; 1/35sec at other speeds.

Why the difference between exposure times at 8fps and other speed settings when shooting single frames? I don't know.. that info comes from exposure times published by Paillard. But I've stuck to the 1/35 second rule (later non-reflex cameras don't have an 8fps setting) and have always gotten proper exposures (assuming I took a proper light reading). :)

Edited by Michael Tisdale, 10 April 2007 - 03:14 PM.

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#3 Nick Mulder

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Posted 10 April 2007 - 04:30 PM

Why the difference between exposure times at 8fps and other speed settings when shooting single frames? I don't know..

It's because the governor is still connected... They are being a little lazy with the technical description for most Bolex users now (who have an active interest in film) as opposed to the hordes of people who used to use them for home-movies who probably had much less interest in the actual mechanics...

It should really read something more like: at 8fps your single frame will give you 1/20th, as you increase the fps it will tend more towards 1/25th ...
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