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Using an external light meter with Canon Auto Zoom


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#1 Josh Bass

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Posted 24 August 2005 - 11:54 PM

Hello. I am attempting to shoot motion picture film for the very first time. I have a Canon Auto Zoom 814 Super8 camera, and I would like to do it like the pros and use an external light meter, rather than the "electric eye".

Here's my problem. I don't know what the fu** I'm doing. I need to set a shutter on the light meter, but I don't know how that works, exactly. I have access to two meters--this super cheapo analogue meter that does spot and ambient, and a nicer digital one that does ambient only. Neither, to my knowledge has shutter angle settings, only time settings. This is what's throwing me off--I don't know how to set that. I found specs on the 814 that says it's got a shutter angle of 155 (it's not variable). I don't know how or if that translates to a "time" setting.

Do you set the shutter "time" on your meter according to the frame rate? If so, the 814 only shoots 12, 18, and 24fps (well, you can do single shot too).

I tried to find a battery for the electric eye, but no luck so far (it wants a 2 zinc air cell, PX625 equivalents, 1.35v), and I figured I'd be able to see what the electric eye wanted, and match the shutter speed on the light meter so that the stop read the same at the equivalent ASA.

I'm shooting on K40, if that matters--indoors, so it'll be the 40 ISO.

Please help. Lost in film land.
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#2 Louis

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Posted 25 August 2005 - 03:24 AM

I think it would help if we knew exactly what kind of light meter you are using, but based on the information you have here, I can suggest this: set the shutter speed on the light meter to 1/45, which is close to 1/48, which I'll assume is your operating shutter speed, because it's standard when shooting at 24fps. (The difference between 1/45 and 1/48 is about 0.06 of a stop). Then, set your film speed to 1/3 of a stop slower to compensate, since your shutter angle is narrower than the standard shutter angle of 180 (if you're shooting with k40, set the light meter's film speed to 32, 1/3 of a stop slower). Now, since I'm pretty much an amateur myself, so this may be completely off, but if I were in your shoes and I had no other information at my disposal, I would at least try this method.
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#3 Josh Bass

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Posted 25 August 2005 - 11:38 AM

Thanks. I'll have to get back to you on type 'o' meter.
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#4 John Pytlak RIP

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Posted 25 August 2005 - 01:52 PM

Exposure time can be calculated, for example:

For 18fps with a 180-degree shutter:

1/18 x 180/360 = 1/36 second.

Do you have an instruction manual for your meter? Have you looked for a copy on the Internet?
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#5 Josh Bass

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Posted 25 August 2005 - 03:22 PM

I believe I've got the copy somewhere, but I think your formula has given me insight. Thanks.


I now realize I've forgotten how to manually multiply fractions. Goddamnit.

Edited by Josh Bass, 25 August 2005 - 03:27 PM.

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#6 Josh Bass

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Posted 25 August 2005 - 03:39 PM

(Sorry, it won't let me edit that last post again)

Ok, I think I got it. Being that my camera does 3 frame rates, 12, 18, and 24fps (oh yeah, and single shot), and has a constant 155 degree shutter, we get this:

for 12 fps: 1/12 * 155/360 = 1/27.9 (numbers rounded)

for 18 fps: 1/18 * 155/360 = 1/41.8 (numbers rounded)

for 24 fps: 1/24 * 155/360 = 1/55.7 (numbers rounded)

Did I do that right? It seems like I did, since I did the math myself for the 18 fps/180 degree shutter example you posted, and got the same answer by the same method.

I basically multiplied the framerate by 360 and divided by the shutter angle of 155 for each one of those. Stupid junior high math.
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#7 Josh Bass

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Posted 25 August 2005 - 07:32 PM

Son of a bitch, it won't let me edit that last post either.

Ok, I don't know where the site that I got the 155 shutter from is, but I found on the "super 8 list" page, that the camera's listed as having a 220 degree shutter. Copied and pasted from there:

"Canon

814 Autozoom

Year: 66-71

Weight: 1720 g

Lens: Canon zoom 1,4 / 7,5 - 60 mm

Microprism Focusing

Auto / Manual Zoom

Frame rates: 12, 18, 24 + single frame

Shutter degree: 220

Manual / Auto Exposure

Fades

No sound

4 X AA batteries

Made in Japan"

Can anyone verify?
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#8 John Pytlak RIP

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Posted 25 August 2005 - 08:20 PM

Okay. Just recalculate with 220 degrees.
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#9 Josh Bass

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Posted 25 August 2005 - 10:08 PM

Done.

A DP friend of mine told me to round to the next shutter speed on whatever meter, since I'd be sure to get some weird numbers.

For example, 12fps with the 200 shutter comes to 1/19.6 , so I called it 1/15.
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#10 Rick Palidwor

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Posted 28 August 2005 - 02:02 AM

I am pretty sure the shutter angle on that 814 is 150 degrees (I am looking at the manual for the 814E, but I think it's the same shutter.) Cameras with a 220 degree shutter usually carry an "XL" designation in the model name, and Canon has several XL lines, and that 814 Auto Zoom is not part of an XL lines, so I would go with 150 degrees.

Rick
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