Bolex shutter, for stop animation

[Damien Bhatti]

Just wondering as I am about to experiment with a stop motion technique - would single exposures with the motor set at 24 fps have the same meter reading if the camera just ran normally? thinking about it - probably yes because you are still shooting with the camera at 24 fps, albeit in a very slow way. Or maybe I am wrong?

[Chris Keth]

I'm pretty sure bolexes have a 1/30th of a second single frame shutter speed. You would have to verify that number with a manual, but I'm quite sure it's different than the 24fps running speed.

[Guest Glenn Brady]

Just wondering as I am about to experiment with a stop motion technique - would single exposures with the motor set at 24 fps have the same meter reading if the camera just ran normally? thinking about it - probably yes because you are still shooting with the camera at 24 fps, albeit in a very slow way. Or maybe I am wrong?

 

It depends upon which Bolex you're using. A Bolex H16 RX and H8 RX have an actual shutter speed of 1/30th for single frame exposures when the speed setting is between 18-64f/s and the exposure control knob/lever set to 'I,' but the adapted speed is 1/40th to allow for the beamsplitter. Time exposures are possible with the exposure control knob/lever set to 'T'. Amateur series cameras - the P1, S1, K2 for example - have a single frame exposure speed of 1/27th when set to 12f/s and 1/30th at all other speeds.

[Guest Glenn Brady]

The 'adapted' shutter speed of a Bolex H16 RX or Bolex H8 RX at 24f/s is 1/80th with the shutter fully open, 1/112th with the shutter one quarter closed, and 1/188th with the shutter half closed.

[Damien Bhatti]

It depends upon which Bolex you're using. A Bolex H16 RX and H8 RX have an actual shutter speed of 1/30th for single frame exposures when the speed setting is between 18-64f/s and the exposure control knob/lever set to 'I,' but the adapted speed is 1/40th to allow for the beamsplitter. Time exposures are possible with the exposure control knob/lever set to 'T'. Amateur series cameras - the P1, S1, K2 for example - have a single frame exposure speed of 1/27th when set to 12f/s and 1/30th at all other speeds.

 

I am using a rex 5 camera. Do you know how to work out the correlation between the shutter speed and the shutter angle of the Bolex for stop motion work. I have a sekonic cine which I set the mirror angle at 135 degrees. (And then I take about 0.3 of a stop off from that reading for the beam splitter)

[Guest Glenn Brady]

While I appreciate the method you describe is accepted by the industry, I think it's an unnecessary complication with the Bolex H16 RX5. If you know the exposure time (1/40th of a second in single-frame mode with the shutter fully open), why do you need to know the shutter angle? Is it just so you can use the Sekonic Cine meter? If the shutter angle is 135 degrees fully open, it should be possible to derive the shutter angle in the one quarter closed and one half closed positions from the 1/112th second and 1/188th second exposure times respectively, but since there are only three detent settings for the shutter (four, if you count fully closed) and the exposure times for these settings are already known, I'm not sure what would be gained by determining the shutter angle.

[Damien Bhatti]

While I appreciate the method you describe is accepted by the industry, I think it's an unnecessary complication with the Bolex H16 RX5. If you know the exposure time (1/40th of a second in single-frame mode with the shutter fully open), why do you need to know the shutter angle? Is it just so you can use the Sekonic Cine meter? If the shutter angle is 135 degrees fully open, it should be possible to derive the shutter angle in the one quarter closed and one half closed positions from the 1/112th second and 1/188th second exposure times respectively, but since there are only three detent settings for the shutter (four, if you count fully closed) and the exposure times for these settings are already known, I'm not sure what would be gained by determining the shutter angle.

 

Yes, with the sekonic i would just dial in the number. When it comes to fractions and the like (ie maths) I am afraid I shrink into the corner, thanks for the info Glenn, D

[Damien Bhatti]

While I appreciate the method you describe is accepted by the industry, I think it's an unnecessary complication with the Bolex H16 RX5. If you know the exposure time (1/40th of a second in single-frame mode with the shutter fully open), why do you need to know the shutter angle? Is it just so you can use the Sekonic Cine meter? If the shutter angle is 135 degrees fully open, it should be possible to derive the shutter angle in the one quarter closed and one half closed positions from the 1/112th second and 1/188th second exposure times respectively, but since there are only three detent settings for the shutter (four, if you count fully closed) and the exposure times for these settings are already known, I'm not sure what would be gained by determining the shutter angle.

 

Sorry I was confused, I understand now, thanks!