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Help with external metering for super 8


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#1 Johnny Gorry

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Posted 24 June 2009 - 11:26 AM

The camera that I am going to be shooting with for an event (Agfa Movexoom 10 MOS) has a shutter angle of 180 degrees.

These are the exposure times listed for the camera printed in the manual:

1/14 sec @ 9 fps
1/28 sec @ 18 fps
1/38 sec @ 24 fps
1/84 sec @ 54 fps

The manual for my light meter (Sekonic Studio Deluxe III L-398A) only makes one small mention of shutter angles in regards to cine metering. It states:

"Note: Some cine cameras posses faster exposure times due to a narrower rotating shutter angle (angle of light transmitting portion). It is important to know the accurate shutter angle value versus cine speed for your camera in order to determine the proper exposure."

That is all that it says about shutter angles and there is no information about how to incorporate this information in to the metering of this device.

I will be shooting Vision3 500T indoors throughout the day and into the night with low-moderate mixed lighting during the day and low lighting at night.

Any help with how to incorporate this information into the proper usage of this light meter for my cine camera would be incredibly appreciated.

Thanks
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#2 susan hawn

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Posted 28 June 2009 - 11:42 AM

Ok, since no one who actually knows anything has answered you, I will give it a stab.

You don't have to use (or even know) the shutter angle since you already know that exposure time at 18fps is 1/28th second. If you didn't know this, then you would need to know the shutter angle to compute it. The light meters I use, which are flintlocks because I can't afford the new percussion cap ones, "triangulate" time, f-stop, and film speed. So as long as you've already been given time, you're golden. The only other tricky bit as you probably know is maybe running some test film to see how much light is "lost" through the lens and finder if a reflex to allow compensation on the hand meter.
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#3 Richard Tuohy

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Posted 28 June 2009 - 05:42 PM

g'day johnny,
I don't think you should simply rely on the data in the back of the manual simply because as susan says we don't know whether this is the actual shutter speed (which is not what you want) or a 'corrected' shutter speed that includes the light loss due to the reflex viewfinder system. You really must shoot a test to calibrate the meter to the camera. Even though you are shooting on neg, you should shoot the camera test on colour reversal film as reversal film will much more clearly indicate 'correct' and 'incorrect' exposures.
Here is a link to my web page on shooting a super 8 camera test:
http://nanolab.com.au/bracketed.htm
cheers,
richard
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#4 Jim Carlile

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Posted 30 June 2009 - 02:48 AM

It's going to be an accurate shutter speed on the back of the manual, but the problem is that this is not the only factor. The big zoom lens and viewfinder optics will soak up some of the light, which means you need to open up the aperture a little bit beyond what the meter tells you.

This means about 2/3 to 1 full stop extra. But-- and here's another consideration-- it all depends upon what Agfa means when their meter says "f/8." It may not really be f/8-- it may be already corrected, with a light loss factored in-- depends upon the camera. So the advice is totally correct-- test it first.

SH is right that if you already know the shutter speed, you don't need that formula-- that's only if you have the shutter angle and need to know the speed (you can of course figure out the shutter angle now just by plugging the shutter speed into the formula with the fps.)

The good news is that V500 has so much latitude that your results will be good no matter what. Even if you just guess the exposure you'll be all right. (but don't!)

Edited by Jim Carlile, 30 June 2009 - 02:52 AM.

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