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Questions about terminology used in Paul Wheeler's "HD Cinematography"

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MD Chought
Questions about terminology used in Paul Wheeler's "HD Cinematography"
on Dec 18, 2007 at 6:02:18 pm

I'm studying Paul Wheelers "HD Cinematography" in order to get a better understanding of how to professionally DP HD Shoots. I've reached part 4 which gets into Lighting for HD and i've run into a few terms i don't understand.
First I don't fully understand what is meant by a cameras "Tonal Range." The book describes how to test for this range, but what is tonal range and why does it need testing?
After it's tested the camera is determined to have an 11 stop tonal range. I once again became confused when this range was compared to a film emulsion in that there is a "straight line section of linear response over most of the range but there is a certain amount of roll off at both extremes of black and white."
What is "straight line section of linear response," and what is "roll off?"


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Steve Wargo
Re: Questions about terminology used in Paul Wheeler's "HD Cinematography"
on Dec 19, 2007 at 6:03:55 am

here's a little bit from a still photo perspective. Studying one frame is the place to start.

http://gug.sunsite.dk/docs/Grokking-the-GIMP-v1.0/node60.html


Steve Wargo
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Bob Cole
Re: Questions about terminology used in Paul Wheeler's "HD Cinematography"
on Dec 19, 2007 at 4:31:20 pm

Nice website! thanks for the link.

re: roll off, other terms. I'm assuming he means that if you had an eleven-step black-to-white chart, with roll-off at the ends you wouldn't be able to tell the difference between the last few chips on either side. iow, the camera can't reproduce the full tonal range accurately.

BC

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MD Chought
Re: Questions about terminology used in Paul Wheeler's "HD Cinematography"
on Dec 20, 2007 at 2:53:03 am

Absolutely, that link spelled it out perfectly. It's always more fun to learn when you know what the hell the author is talking is about.


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Paul Wheeler
Re: Questions about terminology used in Paul Wheeler's "HD Cinematography"
on Dec 20, 2007 at 8:23:53 pm

From the authour,

I am sorry if my book confused you - let me try and explain...

With FILM we can measure the actual density on the negative - known as the relationship between D max and D Min - i.e. the actual measured densities on the negative - and these with a modern negative will have an EQUIVELENT brightness range of 11 stops of exposure.

Film by the nature of recording with silver rolls off, or declines, in its recording capacity towarbs maximum brightness and maximum darkness. Digital cameras, even high end ones, tend to record a very linear line of response - BUT - they can be trimmed to "roll off" if you prefer that.

With high end HD cameras we can only measure BRIGHTNESS RECORDED and again the range will be arround 11 stops of exposure.

In both these cases we are looking for the brightest part of the scene where detail can JUST still be recorded and the darkest part of the scene where detail can, again, just be recorded.

Does this make it clearer?

I hope so.

If not Email me.

All the best,

Paul


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