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Dynamic Range Correction

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Teresa Brown
Dynamic Range Correction
on Apr 4, 2008 at 1:31:20 am

Does anyone have tips how to correct for video shots with extreme dynamic range - either in-camera or in post? (i.e. rooms with lamps or windows, or capturing detail of an architectural diagram on white paper in a conference room scene.) If I expose to minimize blow-out of the bright areas, then pull up mid-range in post, the image picks up unacceptable grain. These are situations when special treatments aren't feasible (such as substituting low-watt lamp bulbs, applying window film).

Dynamic range has been even more problematic on a new Sony HVR-V1u than with GL2. Experimenting with Picture Profile settings. Suggestions?

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Bill Davis
Re: Dynamic Range Correction
on Apr 4, 2008 at 9:29:35 pm

It's never easy, but there are two standard approaches.

The first is to use judgement to minimize the contrast range in the scene. That starts with a visual analysis of your scene followed by making simple decisions such as putting the windows at your back, closing drapes, and/or turning on or off the room lights.

The second level is if you can't control contrast - such as in your "drawings" example - think about doing multiple exposures. Lock down your camera and shoot the scene exposing for the overall room. Then iris down and expose for the drawings. In post, you can easily combine the two shots digitally.

This works equally well when you're shooting high contrast scenics. Lock down you shot and expose once for the foreground - then expose for the sky and combine the two shots in post.

There are other tools such as gradient filters, or simply using a piece of Neutral density gel a little like a photographer might "dodge and burn" a print to expose parts of a scene differently - but there are no hard and fast rules.

Hope this helps.

FCP since NAB 1999
creator: muti-track movies

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Craig Seeman
Re: Dynamic Range Correction
on Apr 6, 2008 at 2:40:39 pm

If you're going to shoot this kind of stuff regularly you might consider a change of camera. Sony EX1 handles wide dynamic range much better than either of the above and there are better cameras than than at a much higher price of course.

Cine Gammas can help. They can roll of the whites a bit and you can bring up the blacks in camera if needed. Any time you bring up something you do risk making the noise visible.

I've been in situations where I've needed to shoot speaker and Power Point presentation. If you can't relight the room (and it seems you can't) you need to inform the client (and charge them) for two cameras (one exposed for speaker, one exposed for presentation).

As you probably know, once brights get too hot they lose detail and you can't bring that back in post. If you bring down bright areas in camera, bringing up black, mids in post can bring up noise. This is where cinegamma can help.

It's much better to get the presentation (architectural diagrams in your case) as separate stills.

So the solutions are:
relight the room (which you say you can't do in this case)
use two cameras
use camera that can handle wider range
use camera cinegamma to roll off highs and bring up blacks
get graphics as separate stills.
fix in post

Generally all my require additional budget. It's important to notify the client about this.

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