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Are all 'f' stop numbers uniform across all formats??...


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#1 James Millward

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Posted 25 March 2009 - 12:13 PM

Just got my first light meter, which I will be using for super 8.

The thought crossed my mind as to whether all f stop numbers were equal to each other across different formats?

eg lets say I had Super8, 16mm and 35mm camera next to each other. All camera were using 100 asa film, and all had the same shutter angle/speed. I then took a reading at it said 2.8.

Does then setting all the cams appatures to 2.8 mean the same exposure will be achieved on all the cams?? ie 2.8 on 16mm is the same as 2.8 on super 8, and is the same as 2.8 on a still camera (given the same asa/shutter etc).

Thanks guys
James
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#2 David Mullen ASC

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Posted 25 March 2009 - 12:19 PM

Just got my first light meter, which I will be using for super 8.

The thought crossed my mind as to whether all f stop numbers were equal to each other across different formats?

eg lets say I had Super8, 16mm and 35mm camera next to each other. All camera were using 100 asa film, and all had the same shutter angle/speed. I then took a reading at it said 2.8.

Does then setting all the cams appatures to 2.8 mean the same exposure will be achieved on all the cams?? ie 2.8 on 16mm is the same as 2.8 on super 8, and is the same as 2.8 on a still camera (given the same asa/shutter etc).

Thanks guys
James


Yes, more or less (a T-stop mark would be even more accurate, exposure-wise). But this assumes the same shutter speed / angle, which is not always the case, some 16mm and Super-8 cameras use shutter angles other than 180 degrees.
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#3 Richard Tuohy

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Posted 29 March 2009 - 05:52 AM

Yes, more or less (a T-stop mark would be even more accurate, exposure-wise). But this assumes the same shutter speed / angle, which is not always the case, some 16mm and Super-8 cameras use shutter angles other than 180 degrees.

and further, the reflex viewfinder system costs the light path some light and the f-stop markings in the viewfinder don't take this loss in to account. Thus if you try and use a hand held meter with a super 8 camera the results will almost invariably be under exposed by a stop or two. Read my page on calibrating a light meter to a super 8 camera:
http://nanolab.com.au/bracketed.htm
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#4 Brian Drysdale

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Posted 29 March 2009 - 06:23 AM

and further, the reflex viewfinder system costs the light path some light and the f-stop markings in the viewfinder don't take this loss in to account. Thus if you try and use a hand held meter with a super 8 camera the results will almost invariably be under exposed by a stop or two. Read my page on calibrating a light meter to a super 8 camera:
http://nanolab.com.au/bracketed.htm


Best run a test.

A few years I shot some Super 8 on a camera that I'd never used before ( I only saw it an hour before shooting with it) and the owner didn't know any shutter speed details etc and the end result was under exposed.

I used the same exposure method that I had used on my own 8mm camera years before and all the Kodachrome shot with that particular camera had been fine.
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#5 James Millward

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Posted 29 March 2009 - 08:12 AM

Many, many thanks for the reply guys. I hadnt even considered the light loss associated with the VF.

I will run some test soon, just trying to get a solid plan together so I dont waste film.

Does anyone know the sutter angle on a windup kinoflex? A few sites have the shutter speed at 24fps as 1/48 BUT I have read elswhere that the shutter angle isnt 180. So how can it be 1/48th??

Lastly, which is preferable, slightly under exposed, or slightly over exposed?? im talking in terms of what could be done later in post to correct.

Thanks again
James
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#6 Adrian Sierkowski

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Posted 29 March 2009 - 10:13 AM

James, depending on just what the angle of the shutter is, 1/48th could be a close enough estimation. I recall on my Bolex days we set the shutter speed between 1/80th and 1/90th depending on what the meter @ hand (Gossen and/or Sekonic) would allow us.
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