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Exposure corrections


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#1 Alex Fuchs

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Posted 08 April 2006 - 02:48 PM

Sorry, there are many threads about metering etc. but I have a specific problem. I shot most of my material on video (min35 etc.) and I'm not really sure, if I understand the mysteries of metering the right way. My question is: I have to shot a music video on 16mm with a beauty colored woman. I asked myself now what is the best exposure. if I put the lightmeter in front of her face to get my f-stop the lightmeter will expose her face like an 18% middle gray, I think, this is not what I want. And I know two, that the caucasian type has an reflection of 30% (does it mean I have to correct the lightmeter value every time down/up to one stop?). So do I have to correct the exposure (maybe about 2/3 stop?) or can I put a greycard in front of her face, do my metering and take this value? Sorry for my bad english, I hope you understand what my problem is. thx alex
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#2 Laurent Andrieux

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Posted 08 April 2006 - 02:51 PM

Do you use a incvident light meter or a reflective one / spotmeter ?
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#3 Alex Fuchs

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Posted 08 April 2006 - 02:57 PM

I use the sekonic 558Cine, and I thought for this situation I want to meter the light in front of her face integral (no spotting, I don't know the english word for this method).
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#4 David Mullen ASC

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Posted 08 April 2006 - 03:12 PM

If you use a spot meter, you'd just have to decide creatively how much over 18% gray in tonal value you wanted the face to be. You may decide that actually she is close to 18% gray rather than expose her face to be one-stop overexposed (opened-up) from the reading that like most people set caucasian skintones.

Otherwise use an incident meter and expose for that reading, then the face would be rendered at its own normal reflectance relative to 18% gray. Or spot meter a gray card.
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#5 Laurent Andrieux

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Posted 08 April 2006 - 03:16 PM

Okay, so let's say you are using the incident metering.

No, it wont make the face look like a 18 % nor do you have to correct for a caucasian skin.

Metering will give you the proper value that would make a 18 % look like a 18 % grey, like it would make a white look white and a black look black (as a quick answer).

It's using a reflective light meter like a spotmeter (what you also can do with the sekonic 558) that need to be interpreted according to the reflectance surface you are spotting at.

If you put a 18% grey card and spotmeter it it should give you the same f stop as the incident light meter (with interger sphere).
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#6 Alex Fuchs

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Posted 08 April 2006 - 03:29 PM

ok, let's have a look if I understand this:

e.g. when I got a a f-stop at 2.0 in front of her face (incident metering) and I expose this 2.0, a middle grey will be middle grey, and her colored skintone will be right. I don't need to do a correction in exposure. Am I right?

By the way: I need the spotmeter only to have a look about the set-contrast all other things I check out with the incident method. I don't really know, if this is the best method to work maybe you can give me some advice what method is the best for what situation. I am a bloody metering-beginner.
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#7 Adam Frisch FSF

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Posted 08 April 2006 - 04:29 PM

Whichever way you decide to meter it, you're going to have to make a creative decision as to if, and how much, to overexpose the face. Black faces can swollow more light than one thinks. Very dark skinned persons (like those from central and east Africa or Australia) can probably be lit 2-3 stops over the ambience.

On my website there's an old video I did for an artist back home in Sweden called Masayah. He was extremely black, not at all brown and warm-ish like he is in the video. I overexposed his face 2,5-3 stops and it looked very good. I was afraid I'd gone too far, but it worked out fine.

Here are some stills:

http://www.adamfrisc.../why/index.html
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#8 Laurent Andrieux

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Posted 08 April 2006 - 09:36 PM

By the way: I need the spotmeter only to have a look about the set-contrast all other things I check out with the incident method. I don't really know, if this is the best method to work maybe you can give me some advice what method is the best for what situation. I am a bloody metering-beginner.


The spotmeter would tell you where a specific spot on the set will be on the stock's curve.

For instance, if your key light is 4 (incident metering), an object that would read a exposure of 4 with the spotmeter will be 18 % grey, one that would be 3 stops under Key light will be black, and one that would be 2 or 3 stops over should turn out white.

As for contrast, you better meter it with the incident light meter. Let's say you have a face lit from left and right directions. The incident reading of 4 may give you the exposure, when the bulb is pointed toward the main camera position. But if you turn the sphere toward the source that lits the right side of the face and then point it toward the source that lits its left side, you will meter the contrast. This subject could give a reading of 2.8 on one side and 5.6 on the other, for instance

ADAM : I like the stills you posted. Just wondering, it looks like you've put his face on a dark backround every time you could, or severly underexposed the bg (may be at timing only ?) am I right ? I mean what way did you grade/time it ? Did you darken the image in post ?
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