AWB-Auto White Balance-has gotten really good in the current generation of digital cameras. They do an excellent job of reading and deciphering most lighting situations that you’ll encounter. So does it make sense to carry a gray card to custom-adjust light balance? Should you learn how to use this old-school device, a true relic from the old Ansel Adams Zone System?
Well, the answer is complicated….it depends! It depends upon the kind of shooting that you do, and how fussy and technical you want to get with your photography. If you like to shoot first, and ask and answer questions later in Photoshop, as in, “I can fix anything in Photoshop,” then no, you probably are not gray-card material.
On the other hand, if you really care about the color in your images, and/or have situations that you shoot in in which color fidelity is really important, then you should carry a gray card and learn how to use it effectively.
I’ll address this post to the second group of shooters.
So when do I pull out a gray card? Basically, in a few specific situations. I do a fair amount of photography in the Louisiana Superdome, and like a lot of domed stadiums, the light inside is some weird mix of sodium vapor, tungsten and maybe even metal halide. In other words, it’s a mess! Relying on Auto White Balance in this location can lead to some strange results. The most common is that the purple in LSU’s school uniforms will usually translate as a deep Royal Blue, using AWB. This is a good case for a gray card exposure. Pulling out a gray card and shooting a quick exposure of it before the start of the game can save you lots of grief later, as I’ll explain below. (Alternatively, if your camera allows, you could shoot a “custom white balance,” but that’s an article for another day.)
Another place I use a gray card occasionally is in photographing artwork. My wife is an artist and I shoot copies of her paintings for her. The gray card is a great way to ensure accurate color reproduction in the copy.
How does a gray card work? This may be oversimplifying, but think about your modern digital camera and its light meter as a computer with a lens on the front. That light meter/computer has algorithms built in for dealing with most lighting situations you’ll encounter, hence the Auto White Balance setting. But when the lighting is mixed, the camera will have a harder time making a correct decision about the light balance. When you pull out your gray card, you’re including a known 18% gray value in the exposure. When you balance this in Photoshop (as explained below), or Adobe Bridge, you give the program a known neutral starting point, from whence all other color values can then be properly calculated.
Below is an example of a mixed-light situation that combines lamp light (in this case, a compact fluorescent source) with evening daylight. Where you place the gray card will have a lot of impact upon your final results. See below.
Carry a gray card with your camera gear. Then, when you find yourself in a mixed-light situation-a shooting environment in which different, incompatible light sources are hitting your subject—pull out the card and shoot a frame of that first. Go ahead and shoot the photograph.
Here’s the easy workflow for jpeg photos:
When you get ready to process the batch of photos from that situation, open up the gray card photo first.
Go to Levels and select the middle (gray) eye dropper from below the Options button on the right. Click on the gray card. You’ll see the colors in the photo clean up like magic!
DON’T CLOSE THE LEVELS WINDOW YET.
To the right of the Preset pulldown at the top of the Levels window is a small icon for Preset Options. Click this open and choose “Save Preset.”
Give it a name you’ll remember.
Now open up another photo from the shoot.
Open Levels. (Cntrl-L on PC, Cmd-L on Mac)
From the Preset pulldown menu, select the preset you made.
Hit OK and voila! It will apply the same toning adjustment to your current photo.
That’s it! A gray card is another nice little tool to have in your box of photo tricks…learn to use one and see what it does for your photography!
Hi, I’m Andrew Boyd, a.k.a. The Discerning Photographer, and I hope this post has been interesting and informative. Please leave me a comment about it, let me know what you’d like to see more of on the site! You can also sign up for email delivery of all future articles or my RSS feed. Thanks!–DiscerningPhotog