January 3, 2008

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 scratc
hes 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.

No comments: