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Exposure, while shooting a dark object against bright light.


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#1 Edgar Dubrovskiy

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Posted 14 November 2007 - 07:14 PM

How do I measure exposure, if I need to shoot a dark object, say, a person against a bright light (window, etc) and want to get his silhouette only? What should I measure to?
Or another example - film strips on a lightbox. And I want the film strips to be black against bright lightbox. Same question.

Thanks a lot in advance!
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#2 Nick Mulder

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Posted 14 November 2007 - 07:55 PM

You need to know the lattitude of your film stock or sensor then simply make sure the exposure is more than half or so that amount of stops below an average reading - a spot meter and a quick read up on a zone system for dummies will do wonders (no disrespect here, I simply mean most zone system stuff is more suited to stills/film and the basics will do for cine) ...

To help out make sure the subjects to be silhouetted are as black and/or lo-con as you can get them then the rest of the scene can be exposed closer to normal (if that is helpful or not is up to you)

Depending on the lighting gear you have you can then spot meter the back light and control how far this will expose relative to the silhouette .

Some form of flagging/gobo work could help if there is other stuff in shot - but without knowing the full picture you expect its no use describing them yet

'Spot Meter' is the word of the day here
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#3 David Mullen ASC

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Posted 14 November 2007 - 08:33 PM

There isn't a right or wrong exposure -- you have some leeway. It partly depends on if you want to meter the shadows and decide how much to silhouette them, or measure the bright window and decide how much to overexpose it.

A close-up of a lightbox is a bit easier -- you just have to decide how many stops over medium gray you want the light panel to be, spot meter the white area, then open up by how many stops you want (three stops over would probably be "normal" bright but not burned-out, and five stops over would be pure white.)

When someone is near a window, I incident-meter what I think should be normally exposed -- for example, I can imagine someone next to the window being half-lit and meter that area, figuring that someone framed against the window will go silhouette. You could also figure that five-stops under on the shadow side should be black enough.
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Rig Wheels Passport

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