Using Your Gray Card

This is the follow up post to "Making Your Own Gray Card".

There are a few methods you can use to obtain your white balance using your gray card:

RAW
One method for using the gray card is to include the card in a test/reference image, shot in RAW format. You can then continue shooting under the same lighting conditions as the test/reference image. For each lighting change, a new test/reference image will need to be shot. Your camera should allow you to shoot in AWB (Auto White Balance) mode. It is important that you read your camera and software instructions to make sure this method can be used.

Transfer the images to your computer using whatever method you are familiar with. Once the transfer of images is complete you can open your RAW conversion software. Most RAW conversion software packages allow you to pick a neutral gray color point on an image to set a custom white balance. You can use the gray card as your neutral color point. You will now be able to apply that setting to all the images shot under those lighting conditions. See your camera and RAW conversion software instructions.

JPEG
Use the same shooting method as if you were shooting RAW (see above) but instead set your camera's image output to JPEG. After you have transferred your images to your computer you can now color balance them in your favorite image editing software. Use the reference image with the gray card in it. Open up the levels adjustment and click on the middle eye dropper tool to set gray point. Now, just click on the gray card and your image is white balanced. Check your software for specific instructions on applying the settings of the reference image to the rest of the images shot under those lighting conditions.

Camera
The gray card can be used to obtain your white balance using your cameras internal white balance utility. Just place the gray card in front of your lens and fill the entire frame with the card and use your cameras internal utility to create a custom white balance. See your camera owner’s manual for instructions.

Make Your Own Gray Card

Quick introduction to gray cards.

White balancing your digital images without a gray card can be hit or miss. Chances are there will be something in the scene that looks gray and using the white balance eyedropper tool in what ever RAW conversion software or photo software you use to click on that gray looking area will make the image look better. But, how accurate is the white balance? Chances are its not that accurate. That gray item in your image probably has some sort of color cast. I'm not going to go into technical detail, but most items that are gray are not completely neutral (have a color cast) and also under different lighting conditions produce a different color cast (not spectrally neutral)

The solution is using any gray card, right? Not always. Some cards were originally designed before digital cameras ever existed and have a color cast. Others are not spectrally neutral. Some can not handle and abrasions, dirt or moisture. While others are just too complicated.

Making your own gray card.

I'm going to tell you how to make a gray card that has no color cast, is spectrally neutral, can be cleaned with soap and water, and the color goes all they way through the material so scratches will not affect it's performance.

What is this amazing material? It's called Sintra®. It comes in 2 shades of gray, light and dark and in 2 thicknesses, 3mm (1/8") and 6mm (1/4"). Both will work for white balancing your RAW images, but the dark gray is closer to middle gray and can be used for white balancing JPEG images. See my follow up post on "Using Your Gray Card". Sintra® comes with a slight semi-gloss finish so that will have to be sanded down with a random orbital sander with 120 grit and then 220 grit sand paper so as not leave any sanding marks. All you have to do now is wash the card and apply Armor All® (optional).

So why did I tell you how to make your own gray card when I sell them on my site? The answer is simple, If you have the ability to make the card yourself...Great! If you don't have the ability to make the card then you can get someone to make it for you, like myself.