Talk:Gray card

message: Isn't it spelled graycard? --Thomas Ploeger 18:38, 27 May 2006 (UTC)
replies: text: 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)
replies: text: I'll move it for you. Dicklyon 06:09, 2 January 2007 (UTC)
thread_title:  Spelling 

message: 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)
replies: text: 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)
thread_title: Caucasian skin?

message: 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)
replies: text: Some real limitations not discussed in the article (taken from Myers): limitations due to material (paint and ink aren't mentioned in the article), too much reflectivity in the red-to-near-infrared, discolouration and degradation due to heat, bluing and fading due under ultraviolet light, gloss, polarisation and durability.  — Preceding unsigned comment added by 77.61.180.106 (talk) 14:10, 29 November 2021 (UTC)
thread_title: Limitations?

message: 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)
replies: text: @solid plastic one: Robin Myers doesn't sell that particular product any more; the conservation target he sells costs $100 and even though I've read his paper on grey cards and I'm sure he knows what he's talking about, I wouldn't be willing to shell out that kind of money for something that doesn't have an online spec sheet.  — Preceding unsigned comment added by 77.61.180.106 (talk) 13:43, 29 November 2021 (UTC)

text: @Amazon: Going by the reviews, those are crap. (I note that half the reviews are 5 stars, but they don't seem genuine when I read them. I don't use Amazon myself, does it have a bot problem?) People are complaining about the manufacturing quality and their reflectivity is also wrong. There are no specs anywhere and I would be very surprised if they were any good in other respects.  — Preceding unsigned comment added by 77.61.180.106 (talk) 13:52, 29 November 2021 (UTC)

text: @painted one: The site's author says he uses Color Place paint; I looked up some reviews online and that brand gets absolutely panned. I realise his cards are principally meant to be as cheap as possible so students can mess about with them and that they're not meant for professional or hobby use, but still...  — Preceding unsigned comment added by 77.61.180.106 (talk) 14:40, 30 November 2021 (UTC)
thread_title: More info

message: 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)
thread_title: Thanks

message: 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)
replies: text: 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)
thread_title:  Achromatic vs. flat spectrum 

message: What is the range of reflectivity (reflectance) of ordinary white paper? What is the spectral curve, of ordinary white paper, and other ordinary white surfaces?-69.87.200.211 12:47, 15 May 2007 (UTC)
replies: text: Depends on what you mean by "ordinary".  Probably 80-90%, fairly spectrally flat.  Problem is, however, that so much white paper is not ordinary, but rather contains fluorescent brighteners, which make for a much more complicated situation than just reflectance, and generally make the paper too blue to use for white-point calibration. Dicklyon 14:28, 15 May 2007 (UTC)

text: The paper industry has to deal with this issue because of metamerism. That's why they make a kind of paper called "true white." It may not be perfect, but it should at least not have the FWAs (fluorescent whitening agents), which are a type of OBA (optical brightening agent). True white is said to be better for printing photos on a computer printer because the appearance is more consistent under various lighting conditions. Zyxwv99 (talk) 13:48, 12 June 2014 (UTC)
replies: text: A lot of paper nowadays does contain optical brighteners, substances that absorb UV and re-emit in the visible spectrum. It's possible to get paper that has an apparent reflectivity beyond 100%, e.g. WestRock produces paperboard with an apparent reflectivity of over 120% in outdoors conditions. Because optical brighteners emit blueish light, the base colour of the paper has to be yellowish to compensate, which creates the unfortunate side effect that papers like this may appear to change colour indoors, usually to a yellow or orangey tint.  — Preceding unsigned comment added by 77.61.180.106 (talk) 10:58, 29 November 2021 (UTC)
thread_title:  white reflectivity 

message: The article should have at least some remarks on the history of grey cards, earliest use perhaps of improvised ones, earliest commercial grey cards, that sort of thing.  — Preceding unsigned comment added by 77.61.180.106 (talk) 10:28, 29 November 2021 (UTC)
thread_title:  History 

message: What is the point of the image if the shade isn't quite right and it's just a rounded rectangle drawn in a drawing program? I feel that unless it's replaced by a calibrated photograph of a real grey card where the shade is exactly correct, e.g. #767676 if its spec says 18%, there really is no point.  — Preceding unsigned comment added by 77.61.180.106 (talk) 14:53, 30 November 2021 (UTC)
thread_title:  Image