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Old November 17th, 2007, 10:30 AM   #1
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Getting correct Exposure Reading using the built in exposure meter

I'll try and explain the issue clearly so folks can understand my question(s).

Typically, during an interview style video, the talent is to one side of the frame with some background taking up the rest of the frame. I try and keep the exposure of the background about 1.5 stops lower than the talent. So what I do is once I've set up the lights (all lights) I then just get the exposure of the background (talent is not in frame and forground lights are turned off. And then I do one or both of the following to get a sense of the exposure of the talent.

1. I bring the talent back into the frame and turn on all lights (keeping the background lights on as well). The composition is the way the shot is going to be.

2. The do the same as above except that I pan the camera to bring the talent to the center of the frame (if the background then seen is also lit) or I'll have the talent in the center and move the forground lights to achieve the same lighting effects.

I get slightly different readings from both (that is when talent is to one side of the frame versus in the center) but I'm not sure that the difference (between background and talent) in exposure is "real".

Another aspects that makes this difficult is that the lighting for the talent is such that one side of the face is exposed more than the other.

So the questions are:
1. How do folks do it?
2. Can one trust the built in light meter and if so how would one use it in this case?
2. Is a light meter essential?

In some cases I find that (usually during post) that the exposure ratio (between background and talent) could be better and I'm trying to get it to a point where it's not a hit and miss thing.
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Old November 17th, 2007, 11:41 AM   #2
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The reflective meter in the camera is center-weighted. Just zoom in to the talent and take a reading, then the same for the background, then set it the way you want. If you're new to metering with a reflective meter, you might want to invest in a Kodak gray card. Have the talent hold it properly in the light so it picks up the key, zoom in and open up or stop down till you get zebras when set at 75%. Do the same for other areas of the frame if you want to see what their readings are.
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Old November 18th, 2007, 12:57 PM   #3
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Bill,

Thank you for your reply.

No I'm not new to reflective meters since every camera that has a built in light meter is reflective and that's the only kind of light meter I've used.

I like your technique of using a gray card. I use this technique in difficult situation in still photography and should have thought to do the same here.

I guess I should have mentioned that I'm using the Letus and so zooming in is not an option (since I use prime lenses). But I think your idea has led me in a direction that should provide me with a solution.

Thanks.

Shiv.
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Old November 18th, 2007, 01:58 PM   #4
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Originally Posted by Shiv Kumar View Post
I get slightly different readings from both (that is when talent is to one side of the frame versus in the center) but I'm not sure that the difference (between background and talent) in exposure is "real".
When you re-aim the camera, if the amount of light in the center of the frame changes, even on the same scene, the exposure will change considering that the in-camera metering system is center-weighted.

The way you describe you do this, it would seem that when the main subject is centered, you would get the more accurate reading in-camera--presumably leaving the background slightly underexposed, as this is how you set the lights.

It seems one solution would be to use a regular light meter to get the proper exposure for the subject and to get the contrast ratio you want for the background.

Then compare the light meter readings with the readings you get with the in-camera systems. After a few setups you should understand what the in-camera system is giving you in relation to what you want.

If you don't have a light meter, perhaps you could use an SLR (spot meter setting?) and a gray card to get readings.

Depending on ASA settings, the light meter (or SLR) may not give the same readings as the SH-A1, but you can still get ratios, and you can use the light meter (or SLR) to understand what the camera is doing.

Again, after a few setups and a little experimentation, you can probably begin relying on the camera.

You can also use a piece of white foam core in addition to a gray card to check exposure using zebra stripes.
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Old November 18th, 2007, 03:03 PM   #5
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Jack,

You're correct in that once I've developed certain "known" ratios I should be able to use just the camera's meter to get it right. It's the arriving at ratios that are meaningful while at the same time comparable that I'm trying to achieve.

I guess there is a solution somewhere between a gray card, zebras and the cetnerweighted metering of the A1.

Wouldn't a white foam core throw off the exposure when using the zebras? Or are you suggesting setting the zebras lower when using a white card instead of a gray card?
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Old November 18th, 2007, 03:41 PM   #6
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Originally Posted by Shiv Kumar View Post
Jack,

You're correct in that once I've developed certain "known" ratios I should be able to use just the camera's meter to get it right. It's the arriving at ratios that are meaningful while at the same time comparable that I'm trying to achieve.

I guess there is a solution somewhere between a gray card, zebras and the cetnerweighted metering of the A1.

Wouldn't a white foam core throw off the exposure when using the zebras? Or are you suggesting setting the zebras lower when using a white card instead of a gray card?
You can set the zebra at 100% or 95% then adjust exposure so that the foamcore just shows zebras or just doesn't. You can use the white to check for hotspots, etc.
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