Talk:Gray card
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[edit] Spelling
Isn't it spelled graycard? --Thomas Ploeger 18:38, 27 May 2006 (UTC)
- This page was requested and I created it - Kodak's preferred naming and spelling is "gray card" (two words, with an A, not an e). I am new here, and don't know how to change the title now that it's created. Furthermore, I will be adding references in the near future. C.anguschandler 05:27, 2 January 2007 (UTC)
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- I'll move it for you. Dicklyon 06:09, 2 January 2007 (UTC)
[edit] Caucasian skin?
Where does this idea of caucasian skin come from? My reading of books suggests that caucasian skin is at least twice as reflective as the 18% card: The Complete Guide to Night & Low-Light Photography. Dicklyon 06:09, 2 January 2007 (UTC)
It comes from Ansel Adams. See "The Negative"; he states Caucasian skin is Zone VI. User:Lexort 20060210.
Does he connect Zone VI to an 18% gray card? This site says skin and zone VI is lighter than the gray card: [1]. Dicklyon 04:49, 21 January 2007 (UTC)
I don't have the book handy any more, but my memory is that he says that skin is VI, and V is 18% reflectivity,and VI is 36% (with VII 72%). This seems clear enough to me - the obvious hard part is that every individual's skin is different. I have had success spot metering on skin with -1 exposure compensation. User:Lexort 20060121T0456Z
Is there any good reason to have a comment about skin of any sort? That's really about the zone system and out of place here. I would like to delete the whole sentence and then this talk section. Lexort 05:05, 21 January 2007 (UTC)
- There was a reason when it was thought to be 18%. Since that was wrong, there's no reason left, and I took it out. Dicklyon 05:16, 21 January 2007 (UTC)
[edit] Limitations?
And I don't understand the limitations section at all. The gray card works in general for setting the exposure of a scene such that objects come out with sort of normal brightness in the image. It doesn't matter if some of them are skin of one or another color. The gray card is also not useful for getting color accuracy, just color balance. A color chart provides no advantage over a gray chart for color balancing, but it could be useful for color accuracy if you system has enough adjustments. It would be best to find a good publication and say what is verifiable, instead of making this stuff up. Dicklyon 06:17, 2 January 2007 (UTC)
[edit] More info
It was my impression that good gray charts are painted with spectrally neutral paint, like the neutral squares on the macbeth color checker, not just printed with a neutral color.
Here's a painted one. And a solid plastic one. Here's where you find the actual size and reflectances of the Kodak Gray Card Plus; and find the Kodak gray card sizes here. Dicklyon 06:27, 2 January 2007 (UTC)
Here's another painted one. Dicklyon 06:32, 2 January 2007 (UTC)
[edit] Thanks
Thanks for all your feedback; I'll get on updating the page, and like I said, get on adding citations, I have some at home, but I'm not there till the end of the week.
C.anguschandler 01:27, 3 January 2007 (UTC)
[edit] Achromatic vs. flat spectrum
It's my sense that "gray card" implies achromatic under reasonable illuminants, but not necessarily flat spectrum. (Certainly good-quality gray cards are spectrally quite flat, and come with specifications.) Thus, I left out flat spectrum as part of the definition. Any photographer who understands color will agree with "if it's not achromatic under D65, A, etc., it's not a gray card", but the flat statement will probably meet with "hmm, that's maybe too strict". This is really an argument about established definitions, so we need a reference. Lexort 13:28, 21 January 2007 (UTC)Lexort
- Here are some I just googled up: Robin Myers PDF, Michael S. Ross. You might want to say that flat is the ideal, and that they are usually pretty close to that. Dicklyon 17:44, 21 January 2007 (UTC)
