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Single Frame Shutter Speed?


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#1 Byron Karl

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Posted 26 July 2016 - 04:08 PM

I'm about to shoot some single frame stuff using a Bauer 715xl and I just realized... I'm not really sure what the shutter speed should be.

 

Normally, I set it at 1/50 as it has a 200-degree shutter and runs at 24fps. However, I'm just assuming that's also the right shutter speed for single frame exposures.

 

Looking over the manual, it seems to only mention TTL metering. No info of shutter speeds. Because of the stock and what I'm shooting, I'm going to be using a light meter and setting the exposure manually. And looking around, I just can't find any confirmation of what shutter speed to use for single frame stuff.

 

Might not be unique to my camera, but a general S8 issue. So please let me know any info that you have. As I have to shoot this week, I don't really have time to do any tests.

 

On a separate note - do I need to compensate for light loss to the viewfinder, when shooting manually with a light meter?


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#2 Martin Baumgarten

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Posted 26 July 2016 - 06:56 PM

At 24fps setting, the shutter speed would be 1/43rd second using a 200 degree shutter opening.  These electronic cameras have an electromagnetic shutter cycle.  Unless posted in the instruction manual, I would use the closest setting to that, however, before entering into any dedicated project, I suggest doing a few experiments first.  Using the same subject matter, try the different running speeds shooting a few seconds and then blocking the lens with your hand, and then shooting the same subject via single frames.   Do this at the beginning or near the end of a film you're using for whatever, make notes, and then compare the exposures. If the image density is the same at run speed as it is at single frame, then you'll know for sure.  A cruder option would be to put a mirror in the film gate at an angle and shoot a single frame and observe the shutter visually.  The human eye is pretty good at noting exposure variations.   You could also use a maglite or similar and place an external light meter in front of the lens and note the reading and compared that to how it appears when the camera is running.  Tricky, but it would let you know if there is much of a difference between the running camera and the single frame shutter speed via the reading you would get.   NOTE:  The meter would be in front of the lens and the maglite behind the film gate.  This won't let you know the correct exposure setting, just a comparison of the single frame and running speed rates.  Since BAUER didn't post the single frame speed in the instruction manual, I would assume that their reason is that it's the same.....BUT.....I still suggest a test to rule out this variable.   Ideally, a shutter speed tester would let you know, but without one, this method will get you in the ballpark. 

 

    As for adjusting the exposure manually to compensate for light loss in the viewfinder exposure prism light-loss, yes.  Usually this should be printed in the instruction manual also.  On earlier cameras it was as much as 1 Stop, on later cameras such as this one, it was less, 1/3 to 1/2 stop.   Keep in mind that the F-Stop reading shown in the camera is the physical F-Stop/Aperture opening, which is used for Depth-of-Field sharpness, as well as exposure settings and variations....BUT is not indicative of the actual amount of light reaching the film.  To compare the two readings using an external light meter, set the meter at the shutter speed, or closest to it, 1/43rd of second (so 1/50th would work). Set the film speed, and read a gray card, or a white card, or something neutral, both with the camera and the external meter and then compare the two.  Since the F-Stop in the viewfinder is the physical F-Stop and not the true indicator of the actual light reaching the film, note the variation and write it down for future use.  It might be slight, not enough to worry about, since so many of these later cameras really have great prisms.   Anyhow, one you have all the parameters and have made your notes, you'll be ready for shooting.   Lastly, although it means shooting a test roll, I still suggest it to rule out any other unforeseen variable.  Good luck!


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#3 Dom Jaeger

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Posted 26 July 2016 - 08:58 PM

As well as the viewfinder prism light loss, the zoom lens also loses light - hardly any S8 zooms were marked in T stops, but typically they lost around 1/2 a stop or more - so together you probably need to open up at least 2/3 of a stop more than an external meter might read. So assuming the single frame exposure is determined by the 24fps speed selection (I think some cameras used the 18fps standard but don't know about Bauers), an adapted exposure time of about 1/80 sec might be a good guess.
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