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#1 casey clayton

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Posted 12 November 2009 - 02:48 PM

Can anyone give me an explanation of why a Grayscale is used everything I have found on the net doesnt really explain it well.
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#2 Tom Jensen

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Posted 12 November 2009 - 03:00 PM

Can anyone give me an explanation of why a Grayscale is used everything I have found on the net doesnt really explain it well.


It gives the colorist or timer a color reference. You shoot it in white light so it's gray. If it has a blue tint at the lab, the colorist will time out the blue. If it's gray then the timer knows not to color out any color that may pop up in the scene. If you wanted a scene to have an overall blue cast and you shot the grayscale in blue light, the color timer might inadvertently color out the blue.

You can also use a gray card for an exposure reference. I've use a gray card on a set with my spot meter to get proper exposure. A gray card will also give the colorist an idea of overall exposure.
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#3 David Mullen ASC

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Posted 12 November 2009 - 07:59 PM

Trouble with color charts for dailies coloring work (versus color tests) is that we all may disagree as to how each colored square on a Macbeth chart should look in dailies, but most of us can agree when a grey scale has a color bias to it versus when it looks neutral.

Now obviously if the cinematographer is going to be there for the transfer session, he may not bother shooting a grey scale at the head of a roll, but for unsupervised dailies transfers, they are very useful IF shot correctly. Generally you would shoot them at the "correct" exposure for the rating that you give the stock, in boring frontal "white" light, something that isn't open to creative interpretation.

Exceptions would be when you wanted the colorist to correct out a colored light hitting the grey card or scale, like when you wanted to remove an overall green bias when shooting under fluorescent lights, or when you wanted dailies to be timed with a color bias (for example, shooting a grey scale under a pale blue light so that when timed to neutral, the scene that follows shot under white light will have a warm bias.)

Grey scales are useful because if the first scene on the roll is not in flat lighting using white light at normal key exposure -- which is most scenes -- then you run the risk of the dailies colorist "fixing" an intentional effect, whether colored lighting or creative underexposure, etc. I mean, other than camera reports, how is the colorist supposed to know what the intended effect is? Lacking any information, he or she will generally opt to make the image as "neutral" as possible, color and exposure-wise. A grey scale at the head of a scene can provide a boring neutral reference by which to judge the creative image that follows it. If you spent a lot of time adding 1/4 CTO to all your lights to give a night interior scene a warm golden bias, you generally don't want that timed out in dailies. If the first shot on a roll is supposed to be in moonlight and is blue-ish and underexposed, the timer may try to make it neutral in color and brightness, not knowing that it was supposed to be moonlight.

I often follow the grey scale with a sign with a generalized description of the look, like:

COLOR: WARM GOLDEN LOOK or COLOR: PALE BLUE MOONLIGHT or COLOR: DEEP BLUE TWILIGHT or COLOR: ORANGE FIRELIGHT, etc.

I even have a few signs printed that read: COLOR: LEAVE GREEN FLUORESCENT LOOK UNCORRECTED

This way, even if dailies are mistimed, the director, producer, editor, etc. might still see that note (assuming the colorist puts it into the dailies) and know what was intended.
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#4 Adrian Sierkowski

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Posted 12 November 2009 - 08:56 PM

Oh David, I think I'm going to have to steal that (painfully obvious in hindsight) idea of notes after grayscales.
I have a nice Kodak gray card (18%/White/Black) that I often have someone (a PA normally) Hold next to their head so as to get the scale and a skin tone in 1 shot, for what it's worth.
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#5 casey clayton

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Posted 13 November 2009 - 03:49 PM

Thanks very much
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#6 Chris Keth

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Posted 17 November 2009 - 07:02 PM

In testing, a greyscale (in combination with spotmeter readings for each chip) can help you see how much the gamma of the film is being increased or decreased by non-normal processing.
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