What's up with custom white balance

You may have seen my picture Floating rose but what you may not know is that it was shot under horrible lighting conditions. I was in a room with a single light source (an old halogen lamp) pointed toward a standard drop ceiling. It was bad. Really bad. But I thought it was an interesting shot so I decided to make some changes to my camera (should be standard practice, by the way). Here is my original shot:

As you can see it's horrible. But was I worried? Nope, not one bit. It's easy to fix, and there are two ways to do it. 1. Change your white balance in your camera 2. Fix it in post I opted for #1 but my best shot happened to be my first one, before a custom WB was set on my camera. No worries. First, I had to take a picture of a neutral density. I carry a set of cards with me so it's usually no problem. Here is my original shot of my neutral card:

Now the best thing to do is to use this shot and set your camera to a custom WB by pointing to it, and I did that. But remember that my best shot happened before this. In Aperture (or Lightroom, PhotoShop, whatever) I set my white point to the gray card, and that gave me this pleasing, corrected colorful shot:

I simply lifted the adjustment on that shot and applied it to my horrific rose shot and look at the magic that happened:

Yay for the custom white balance! This is my most dramatic example to date of what setting a correct white balance can do for you. As I said it's standard practice for me now at all shoots.