Use an 18% Gray Card for Better Color Balance in Your Photos

If you've ever relied on your camera's white balancing algorithms you know how imperfect they can be, but you're not out of luck. Getting accurate color balance with just about any camera is pretty easy with an 18% gray card.

A Gray Card for Staged Photos

You might think it makes more sense to balance the white in your images, given that the term we use most often is "white balance," but since we're looking for all-around color accuracy the best balancer is gray. Why? It's the average tone and it's neutral. If you're sampling the white for color balance you're just sampling the high end of the spectrum (or pure white, if your photo is overexposed). In fact, when your camera is white balancing it's (generally) looking for a neutral gray area. The use of the 18% gray card is basically to tell your camera, "look, the neutral gray is over here!" Technology blog Tested explains how to use a gray card for a portrait photo:

Place the gray card where the subject will be, so the light hitting the gray card is the same as the light hitting the subject. If shooting a portrait, have the subject hold the gray card in front of their face for a test shot. When you process your photos later in Photoshop, look at the test shot. Enter the Image > Adjustments > Levels menu, and click on the middle eyedrop icon. Save the level adjustment, and then load it in every other photo under those lighting conditions. You've just color corrected your shots with a gray card.

A Gray Card for Everyday Photos

While it's always best to have a reference shot with the gray card in your photos if you want to edit them later, a gray card can help you out for your everyday shots as well. If you're staying in one general location, say for a family barbecue or someone's birthday party, you can use a gray card to manually set the white balance of your camera. How this will work will vary from camera to camera, but generally you'll find this option wherever you'll find white balance settings. From there, all you really have to do is make sure the card fills up most of the frame as you tell your camera to white balance based on what it's currently looking at.
If lighting conditions stay generally the same during the day, manually setting your camera's white balance with a gray card should get you better, more accurate color for all your shots. Just remember you'll need to rebalance every time you move locations, or turn automatic white balancing back on if you're feeling lazy.

Making a Gray Card

While you can pick up an 18% gray card at most photography supply stores, you're basically buying a piece of gray board. The benefit of buying a card is that you know you're getting exactly 18% gray. If your photos aren't going on the cover of a magazine and you just want better accuracy in general, you can print out a gray card from your computer. If you just pick a middle-of-the-road gray and print it out, it'll be a good start. Here's an easy way to do this:

1. An easy way to do this is open up Photoshop (or any image editor that can handle layers) and make a new document that's sized at 8.5" x 11" and has a white background.
2. Make a new layer and fill it with black.
3. Reduce the opacity of that layer to 50%.
4. Print.

If your printer has a color profile, you may want to switch to that before printing for more accurate results. I did this with a cheap laser printer, however, and it worked really well. My gray card was uneven and pretty horrible in general, but I still ended up with better and more accurate color than the camera's automatic white balance. A proper gray card is definitely better, but when you need something quick you can get by with even this fairly inaccurate method.
Of course, if you want to make a really accurate gray card you should go for it. There's a great explanation of finding 18% gray on the photo.net forums that'll help you get there.