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Light Meters


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#1 Jim Malone

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Posted 23 January 2008 - 03:53 PM

Can anyone tell me about using light meters for digital video? Would one be helpful? Has anyone ever used one before shooting digital video? What would the pros and cons be. Any information anyone could give me on this matter would be greatly appreciated.

Cheers!
Jim
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#2 Adrian Sierkowski

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Posted 23 January 2008 - 04:02 PM

Normally for video you'd expose either based on a waveform on set or based on the zebras in your viewfinders. Digital cameras, as I have been told, don't really have an ASA. You can try to ball park some, though; to get a rough estimation or overall exposure, but meters on video aren't nearly as useful as the IRE readings on a waveform monitor.
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#3 Jim Malone

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Posted 23 January 2008 - 04:09 PM

Unfortunately my camera does not have a waveform monitor, nor do I have an external waveform monitor to hook up to it. It does have zebra bars though, but I find their use in setting the exposure somewhat limited.
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#4 Valerio Sacchetto

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Posted 23 January 2008 - 04:24 PM

You can use a lightmeter to light the shot. A stop is a stop on both mediums and if your lightmeter reads in footcandles you can balance your lighting. Don't use it to set the exposure tho. quite useless and dangerous.
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#5 Jim Malone

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Posted 23 January 2008 - 04:48 PM

Maybe I miss the point of a light meter. If you aren't using it to help you properly expose your image, what are you using it for? I thought the point was to know what f-stop to park on.

Please advise.
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#6 John Brawley

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Posted 23 January 2008 - 05:06 PM

Maybe I miss the point of a light meter. If you aren't using it to help you properly expose your image, what are you using it for? I thought the point was to know what f-stop to park on.

Please advise.



I think Valerio is saying that it's useful to know the RATIO of brightness within a scene. So your subjects face can be measured as 1 stop brighter than the tone on the wall behind their head. No matter how you then expose that shot, you'll always know that the face will be brighter than the wall behind by the same amount.

And so, yes it's useful to be able to MEASURE light, then interpret the readings and infer an exposure setting from that. Even on film, rarely would i actually set the exposure on the lens to what the meter says. It's usually not that literal because you are always evaluating what you're shooting, how reflective the subject is, and how you actually want it to look.

For example, If I was shooting day for night, the reading from a meter is only going to give me an exposure for getting it right as a normally exposed daylight level. I have to then decide how much to underexpose it to get a good day for night.

Make sense ?


jb
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#7 Valerio Sacchetto

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Posted 23 January 2008 - 05:38 PM

Spot on John.
I wrote a bit in a hurry so i apologize for the simplistic answer.
I also implied that if your meter doesn't read in FC you can't balance your lighting which is wrong. With FC you have an absolute value independent of your meter settings (ASA, FPS, Shutter angle...). Very useful IMHO.
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#8 Deepak Bajracharya

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Posted 23 January 2008 - 06:20 PM

Namaste,

I frequently use the incident light meter for my work on DVcam format specially indoors where I wanted to maintain the specific lighting ratio which I found very helpful.

I use to set the meter in 400ASA in 3200 degree kelvin, the camera being DSR390 for the reference and set the lighting ratio accordingly and put the aperture cross checking with the auto exposure mode.

With best regards,
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#9 Mike Williamson

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Posted 23 January 2008 - 08:24 PM

I often use my meter to get an estimated stop at whatever ASA I've roughly determined the camera to be working at, then I'll take a look at the monitor and zebras. What it's most useful for is in maintain consistency between set ups, so I have an incident reading at a specific ASA (or footcandle reading) to match. So if I bring in a frame for a close up, I have a measurement of how much light I need coming through it.

Plus it puts me back on a scale that I understand. I know what 2 stops under vs. 1.5 stops under looks like, but I couldn't tell you the difference between 20 and 30 IRE before it. I think in stops, so it helps me to say "let's get it one over" rather than "I need 75 IRE on that back wall".
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