The white area in the second picture may appear a bit yellowish because of the surrounding predominant yellow and green cast. But when I isolate and enlarge it, it is indeed white. The second pictures color is also closer to the real item.
Ok, let me explain. The card is divided into four segments. Namely, the Highlight (white), Shadow (Black), Midtone (Dark Gray), Camera Raw White (Light Gray).If you do PP, I think they would ring a bell already. This card actually simplifies the color-correction process.
When you have a very challenging but consistence light condition, include the card in your first short. Then continue to shoot normally. When you open your first photo, you can quickly determine the highlight, midtone and shadow area. And by clicking the corresponding eyedropper, (whether in Levels or Curves) the photo will correct itself. No more guessing! You can then copy this adjustment layer setting into the rest of your photos.
Camera's AWB
Adjusted in Photoshop
Adjustment layer copied into the second shot
You can also use the white area to customize your camera white balance and the Midtone for exposure metering. (Not so important for digital but very useful for Film/Slide).
Hope it helps. And oh, if you want to know, I got it from a book I bought. Dont know if camera shops got sell or not.:dunno: