This card has three cards, white, black, and gray, so you can use it for RAW or for JPEG (see more below). The user's guide is helpful, but not super technical. The price is unbeatable for what you get. Shipping is fast. I used this card to shoot a friend's wedding and the results were fantastic! Basically this is a cheap and easy way to get perfect colors in your digital pix.
Before I got this white balance card, I got a whybaL G6 card, which was a lot more expensive. Shipping was a bit slow, and when it arrived, I was disappointed because it has only one card, and the user's guide on CD-Rom they show in the picture either is out of stock or never existed because they wouldn't send me one when I asked. My colors have been super accurate with the Digital Grey Kard - I don't think it's worth spending more than twice as much to get the wHybAl card.
I shoot RAW files mostly, and in Photoshop or Photoshop Lightroom I use 1-click white balance in the RAW converter. During a photo shoot I simply shoot an image of the gray card under the same lighting conditions as my subject. Then in post-production (I use Photoshop Lightroom) I open the image of the Digital Grey Kard in the RAW converter. I use a 5 pixel white balance dropper to get a good sample of the color of the gray card. Then I select all of the images that were shot under those same lighting conditions, and click the 'sync' button, making sure I sync the white balance only. That's all I have to do to get perfect color. Fast, accurate, easy.
When I shoot JPEGs, I am glad to see that Adobe Photoshop Lightroom will still allow me to do some white balance correction, essentially using the same steps as outlined above. But with JPEG, the image quality is degraded somewhat by the process, so RAW is a better way to go.
There is another way to get great white balance for JPEG using this card. The Digital Grey Kard is also perfect for setting in-camera white balance, which actually is the best way for JPEG photographers to get perfect colors without having to use Photoshop or Lightroom. The user's guide included with the cards makes this easy.
I use the white card and the black card sometimes to set levels in Photoshop. To set the white and black point in the Photoshop "levels' control, I shoot an image of all three cards, and open the image in Photoshop. I go to image->adjust->levels an use the highlight dropper tool on the white card and the shadow dropper tool on the black card, finally I use the midtone dropper tool on the gray card. This technique is great for setting up a JPEG for maximum dynamic range - which allows you to take advantage of the full capabilities of the output printer or display device.
This is a great color correction tool every digital photographer should have. Get this white balance card - it's great for the money.