 Desiree C. Preckwinkle |
GRAY cards... is there any left?????? I am in need of a gray card and the kodak one I ordered a month ago is still on back order... so I bought one at a local store and it did not have the white back side, only gray and instructions for the zone..... So do you know of any other brands that I could search for that have gray cards in stock that also have white on the other side so I can set my white balance??? thanks and please let me know,. Desiree
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Mark Feldstein |
You can probably go to either a stationary or art supply store and buy a piece of medium gray poster board, carve it up into 5x7 or 8x10 or even wallet sized pieces. Tape an unlined 3x5 card to the back and...well, use your imagination. M.
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Melissa Manheim |
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Melissa Manheim |
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Christopher A. Walrath |
You can also use your hand as a reference. Meter the shaded portion of your hand and, as your meter reads it as 18%gray, anything else that matches those readings in your subject give you a frame of reference for exposure. A good exposure level for caucasian skin is about zone VI (one exposure value above 18% gray). Apply a zone VI value to anything in your subject that matches and adjust from there.
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Alan N. Marcus |
All good advice: I too, have looked about for common objects that can be used as a substitute for a gray card. Like Mr. Chrisopher W, I have often use my hand, adjusting the exposure for zone VI which means my hand reflects 1 f/stop more light than a 18% gray card. Consider that gray PVC pipe is about the correct shade. Go to a hardware store and buy one tiny fitting for under a dollar. Now go to a craft store and buy construction paper, attempting to match the pipe. Now go to any one-hour shop. Ask them to measure the construction paper with their reflection densitometry equipment. Most will be happy to oblige. The correct reading 0.75 red 0.75 green 0.75 blue. These are reflection density values. One f/stop is 0.30. The permissible gray value error is 1/3 f/stop which is 0.10. Thus the three values can be dispersed with no greater spread than + - 0.10. These values are good to tests existing gray cards for fading etc. The value 0.75 is logarithmic base 10 which is the scale unit of this science. This value can be expressed as an ordinary number. When converted the value 0.75 is written as 5.62 – this is the antilog of 0.75. It might be thought of as the filter factor of an object with a 0.75 density. Consider 100 watts (units) of light is directed onto a surface. Should 18 watts (units) be reflected, 82 watts (units) are absorbed. Now to calculate using the filter factor: 100 ÷ 5.62 = 18 (rounder up) or expressed as a percent (per one hundred) written as 18%. This is the amount of energy reflected. This perplexity is my way of explaining the origin of the gray card value of 18%. Alan Marcus
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John H. Siskin |
Hi Disiree, If you are doing a balance on a grey card in order to control color, close is not really ok. I use a GretagMacbeth Colorchecker when I photograph art work. When you copy a painting close is not good enough. How will you fix it later if you don’t have the original? For other uses a less expensive piece of cardboard would do. You might even print out a grey card with your printer; this would be a very cheap option! Thanks, John
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