Correcting White Balance

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Getting the correct white balance in a photo can be tricky. The white balance settings on cameras (auto, daylight, shade, cloudy, tungsten light, fluorescent light, etc.) can get you most of the way toward where you need to be, but sometimes the setting of the photo itself makes it tricky to correctly capture the white balance.

Just to give you an example of two photos taken in the same light conditions but using different white balance settings, I’ve volunteered my cat Oz to pose for you. He’s happy to oblige, despite the expression on his face. And yes, he got into the laundry basket on his own. If I’d PUT him in the basket he would have just leaped out again, immediately.

Anyway. This is a shot with the “tungsten” (incandescent) white balance setting:

Model Model

This is a shot with the “fluorescent” white balance setting:

Blue Hue

Not my best work, but I think they illustrate my point.

In order to capture the correct white balance for a photo or a series of photos shot under the same light conditions, it is helpful to have a swatch card. This is a white or gray card (some cards have four squares of white, dark gray, light gray, and black). This is used to “tell” the camera (or post processing software) what object in the photo is white, and is supposed to be white in the picture. Then the camera (or software) calculates the difference between the white of the picture and “true” white, and adjusts the color scale and temperature of the entire photo accordingly.

It sounds more complicated than it actually is.

As inferred in the text above, there are two ways to manually set and/or adjust white balance. One is on your camera itself (if you have one of the more recent digital SLR’s); the other is in your photo editing software (for this example I’ll be using my ever-trusty Photoshop CS3).

Specifically for my Canon Digital Rebel XTi (similar steps apply for other camera brands, check your camera’s manual), a “custom” white balance setting is achieved by photographing a white object or photographing your subject holding a white card (for even better accuracy, an 18% gray card can be used – the why’s and wherefore’s and technical mumbo-jumbo explaining that can be found here) – under the lighting conditions that will be used to take the subsequent photographs.

Step One: Focus on the swatch card and set the correct exposure. Take a picture of the swatch card.
Step Two: Select “Custom WB” under the White Balance settings.
Step Three: Press “set”. The “set” screen appears.
Step Four: Import the white balance data by selecting the image captured under Step One, then press “set” again.
Step Five: Select the custom white balance settings by going back to the White Balance menu and selecting “Custom”, then press the shutter half-way to set the white balance.

In Photoshop CS3, it’s even easier to correct the white balance, and is the method that I personally prefer:

Step One: Take a picture of the swatch card or white object you are using as a reference point, as above (make sure the lighting and exposure is identical to what you will be using in your subsequent photographs).
Step Two: Open the file that contains the photo of the swatch card, in Photoshop.
Step Three: Open the Curves dialogue box (keyboard shortcut: Ctrl-M). If you’re using a gray card, select the gray eyedropper and click it on the gray card (white eyedropper on white card, black eyedropper on black card – also, if there is no card in the shot, simply click on an object that you know should be black, gray, or white). Use all three eyedroppers if you’re using a card with a spectrum of white/gray/black, or have white/gray/black elements in your photo.

I adjusted the black balance in this step by clicking on the black chair in the background of the photo:

wb1

I adjusted the gray balance in this step by clicking on the CPU under the desk, which is gray:

wb2

And here’s the re-balanced photo:

wb3

Here’s the “before” so you can compare without having to scroll:

Blue Hue

Step Four: Now that you have the Curves settings where you want them on the first image, you can apply them to the subsequent images. Open each photo individually (keeping the original photo open), then open the Curves dialogue box to apply the same settings. Alternately, with multiple photos open, you can “drag and drop” the adjustment layer from the original photo to the photo you wish to adjust.

Photo Credits (in order of appearance):
- “Model Model”. Photo by Laura Charon.
- “Blue Hue”. Photo by Laura Charon.
- “Starbucks Chairman Howard Schultz Holds Up White Balance Card”. Photo by sillygwailo¬†on Flickr Creative Commons.

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