Color Balancing Options

OK, so there is a thread where the topic was brought up about color balancing cards.  So now I am going to try and give a brief explanation about the uses and advantages and possible problems with using them.

There are basically four options: white card, grey card, three tone gray scale card, and a multi-color card.  All of these will meet the desired end if used properly.

All you need to do is take one photo with your subject holding it in each new lighting condition.  Are you tired of green shadows in open shade under trees?  You will love this.  Is it completely fool-proof?  Of course not.  Actually, it would [arguably] be more accurate to use an ExpoDisc, but they are a topic for another time, and are also not foolproof.

So, the white card and the gray card do more or less the same thing.  They are going to set your white balance for your images.  There are two main methods to doing this (or you can do both, probably the best).  You meter your scene and set your exposure first, this will help make the measurement much more accurate.  Then, you set your camera to its 'Custom' white balance setting, hold (or have someone hold) your card parallel to the film plane of the camera, fill the frame with the card, and take a photograph of it.  The camera will automatically set your white balance for the current light temperature and you will get some very consistent color in your images.  You will need to read your camera's manual to find out exactly how to get the camera setup to do the custom white balance, but the rest of the steps will be the same.

OK, so you have your custom white balance, why use the others.  Well, the three tone card and the multi-color card have a little more use after the fact.  You can use those to dial in the image better in Bridge and/or Photoshop.  If you use the three-tone card (my preference) then you can use the eye-dropper to sample the black, gray, and white stripe and then balance all the tones in the image in Bridge before ever opening them in Photoshop, or use them to color balance in Photoshop (either way).  The multi-color card is great for very precise color work because you can adjust all your colors until the RGB values match their calibration specifications, again by sampling the colors with the eyedropper.

Now you know a little about them, here is a link to Gretag Macbeth's site that shows them all.

I want to also make a few things very clear...
-These will only be accurate with accurate exposure.
-These will only be accurate if the card is parallel to the film plane (or close to it).
-Make sure your hand is not casting a shadow across them when photographing them (evenly lit cards will cause a lot less frustrations).
-Use it in EVERY new location or setup for the most consistency.
-Use them in the same spot your subject is going to be.  Ten feet in front of them will do you no good, and if there is a color cast from reflected light, it's even more important to be in the same spot as, say... their face.

And, just as a personal recommendation...
I like to use a gray card and set a custom white balance first, then also shoot the three-tone card to finalize my adjustments in post-processing.  I am seriously considering replacing my three-tone with a multi-color, but that is only because I am anal about my colors and prints.  I don't mean that in a bad way to anyone, most people probably do not need this unless you are VERY concerned about your portraits and/or doing commercial work that requires perfect color rendition.  The commercial work is what I want to get into and is the reason for my consideration.

I feel like I've left a lot of gaps in this explanation, so feel free to ask questions or make corrections if needed.

Travis