Kirby Fong, California

about gray cards and backgrounds for photographing daffodils

March 12, 2009

Category: General

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There have been a couple questions about the background for photographing daffodils and about a gray card in particular. Let me start with the background color.
I think the choice of background color is a matter of personal preference; at least I’ve never heard anyone give a reason why it should be blue, black, gray, or any other color. Black certainly makes the subject jump out more dramatically. Gray is quite neutral. I happen to like blue because I think it is generally a good complement to yellow and white perianths and because it is less likely to cause automatic exposure to over expose the image than black. Black on the other hand can more easily hide shadows if you have a light shining straight at the flower. With any color other than a matte or dull black, you have to be careful to position your light so that the shadow of the flower is not in the camera’s view.
Automatic exposure in cameras is based on the assumption that the scene will reflect 18% of the light that falls on it. I don’t know who determined the average reflection or whether it is really 18%. Having a background that reflects 18% of the light that falls on it will make your scene more average so that automatic exposure is more likely to be right. This is the advantage of the 18% gray background.
Kodak (and probably others) made (and might still make) 18% gray cards. I bought a set in the early 1990s for $6.95 that included one 4×5 inch card and two 8×10 inch cards. Kodak says of their cards, “The card is specially manufactured to photographic specifications. The gray side reflects 18% of the light falling on it, and the white side reflects about 90%. Also the gray side has a protective lacquer overcoat that reduces specular reflectance and resists damage from fading, fingerprints, soil, etc.” The way the card is meant to be used is to meter off of it to set the exposure manually on your camera. Then you photograph your subject under the same light where you held the card to take a meter reading. This gets the exposure right but says nothing about whether there is a color cast in your light. In particular, incandescents tend to give orange casts and fluorescents a green cast.
My purpose in photographing the green daffodils with the 18% gray card was to allow subsequent adjustment of the color balance to show the green accurately. This depends on Kodak’s claim that their gray card is neutral – i.e. has no color cast because it reflects equal amounts of red, green, and blue. By including something in the photograph that is known to be neutral, you can later use a photo editor like Photoshop to adjust the whole image so that the neutral parts become neutral. This fixes deficiencies in color balance caused by the light or inaccuracies in the camera’s sensor.
I must add though that if you get a reasonable exposure, most daffodil colors will in turn be reasonably accurate even with blue or black backgrounds. The only color that seems to be elusive is green, with many photos of green daffodils making them look yellow.
Kirby Fong

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