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Film Latitude/Dynamic Range


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#1 Jared Williams

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Posted 14 December 2009 - 08:58 PM

Hello all,

This is my first post. I'm a student and have mainly shot digital and last week finished my first project on 16. It was stocks 7219 and 7205. I should be getting footage back by the end of the week. It was transferred best light to HDCAM.

A question I have deals with the film handling overexposure. With the HVX or EX-1 I have found myself really having a issue with clipping in EXT. shots where there is a wide spectrum of shadows and highlights and something 2 stops over can clip.

I found myself in a regular situation (no ultrabounce or HMI's) where I had a shot that was backlit and a exposure difference. Through some help from these forums I underexposed a bit but my background was 2 stops over. I have done the same with digital and always find myself clipping and needing to adjust the shot a lot in post to make it right. With film will I find 2 stops to be too much? Should I have underexposed more? I was a stop in a half under (with incident) in the shadows. Before shooting I remember my teacher saying film likes the highlights and digital sees in the shadows.

So I am just hoping to get a decent image that with some slight tweaking I will be happy.

Also what is the difference between Latitude/Dynamic range? One I hear a stock has 7 stops latitude then I heard 16 stops dynamic range. So I am a little confused.
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#2 David Mullen ASC

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Posted 14 December 2009 - 11:50 PM

Either way, you have at least another two to three stops of overexposure detail with color negative over digital. Digital has almost no latitude for overexposure -- even a two-stop overexposure is hard to correct back down to normal.

The confusion over naming a range is that there is a difference between total measurable range and a workable, practical range that takes into account that a film print or video display generally has to use a smaller range than the original. Plus many ways of measuring dynamic range count detail recorded in the extreme low end which is usually too noisy or grainy to be usable detail.

So while I can tell you that the general idea is that the best digital cameras have something like 11 to 12 stops of dynamic range and film negative has something like 15-stops of dynamic range, you generally won't find that much range to be usable in your work, you have to count on a narrower range. For most digital cameras, it's more like an 8 to 10-stop range max and for film it's more like a 10 to 12-stop range.

Generally "latitude" means the range that is correctable, the degree to which one can correct an image, while "dynamic range" refers to the total range of exposure values that are recorded. So latitude is a much smaller range than dynamic range. For example, you can record detail that is five-stops underexposed on both film and digital, but that doesn't mean that a shot that is five-stops underexposed is correctable back to normal.
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#3 Brian Pritchard

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Posted 20 December 2009 - 11:38 AM

Also what is the difference between Latitude/Dynamic range? One I hear a stock has 7 stops latitude then I heard 16 stops dynamic range. So I am a little confused.


The dynamic range is the distance in stops from the toe of the curve to the shoulder. It is a measurement of the usable range of the curves. In the case of 7219 the range is 15 stops. That is the difference between your minimum exposure for shadows and maximum exposure for highlights.
Latitude is a measurement of how much you can overexpose from the minimum exposure that will record your shadows without crushing, to an exposure that will record your highlights without crushing. The latitude is entirely dependent on the brightness range of your scene and the dynamic range of the film. If you are shooting a gray card in a fog you will have a very low brightness range say 1 stop. In this case the latitude of the film would be 14 stops. If you are shooting a scene with a high brightness range, a polar bear in a coal cellar and the difference between the highlights and the shadows is 6 stops then the latitude of the film is only 9 stops.
Brian
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