Appendix C: How to Use the Gray Card and Color Checker

Perfect and consistent color doesn’t happen by accident. Knowing how to use your included gray card and color checker could save you a lot of postproduction hassle. While they aren’t tools I would often use at a wedding, they are a must-have for studio or product photography.

The Gray Card

The color temperature of light varies and is dependent on the source from which it comes. You may even see variances in color temperature from the same light source, such as a speedlight or studio strobe, when the power settings are changed. Color temperature changes can also occur as the light source ages or, in the case of the sun, as it moves across the sky. Although you may believe that you have a neutral item in your scene from which you can select a custom white balance (), the best way to know for sure is to use a gray card. A gray card is designed to reflect the color spectrum neutrally, providing a standard (or baseline) from which you can measure white balance in other images taken within the same scene and with the same light source. By taking a test shot that includes the gray card, you guarantee that you have a neutral item against which you can adjust colors later if you need to. Make sure that you place the gray card in the same light as the subject for the first photo, and then remove it and continue shooting.

TIP When taking a photo of a gray card, de-focus your lens a little to ensure that you capture more even color.

My software of choice for cataloging, culling, and editing images is Lightroom. In the Develop Module, Lightroom allows you to use the White Balance Selector to select an area of the image that is completely neutral, thereby eliminating any unwanted colorcasts. By placing and photographing your gray card in the first image of your series, you can refer to it later in Lightroom (or your preferred image-editing program) to apply the correct custom white balance.

If you prefer to make adjustments during a shoot (and if the lighting conditions will remain mostly consistent while you shoot), use the gray card, or a tool called an ExpoDisk, from ExpoImaging, to set a custom white balance () in your camera. You can do this by taking a photo of the gray card or ExpoDisk, and filling as much of the frame as possible. Then, use that photo to set the custom white balance () in the Custom Setting menu () of the camera.

The Color Checker

A color checker contains 24 color swatches that represent colors found in everyday scenes, including skin tones, sky, and foliage. It also contains red, green, blue, cyan, magenta, and yellow, which are the colors used in most printing devices. Finally, and perhaps, most importantly, it has six shades of gray.

The process for using a color checker is very similar to using a gray card. You place it in the scene so that it is illuminated in the same way as the subject. Photograph the scene once with the color checker in place, and then remove it and shoot away. You should create a reference photo each time you shoot in a new lighting environment, or when you change power output settings on your speedlight or studio strobe.

In Lightroom, open the image containing the color checker. Measure the values of the gray, black, and white swatches. The red, green, and blue values in the gray swatch should each measure around 128; the black, around 50; and the white, around 245. If the camera’s white balance () was set correctly for the scene, your measurements should fall within the range (deviating by no more than 7 points either way). If so, you may rest easy knowing that your colors are true. (Isn’t there a song about that?)

If your readings are more than 7 points out of range either way, you can use software to correct the image. You can also use the levels adjustment tool to bring the known values back to where they should be (gray around 128, black around 50, and white around 245).

If you prefer to shoot JPEGs rather than RAWs and your camera offers custom styles, you can also use the color checker to set (or adjust) them. Simply take a sample photo and evaluate it using the on-screen histogram (preferably, an RGB histogram if your camera has one). You can then choose that custom style for your shoot — perhaps even adjusting it to better match your color expectations. This will have no effect on your RAW image.