I think I went through the idea of how the camera’s light meter see’s everything as 18% gray and unless corrected will render white or black scenes as a middle gray. Here’s an easy way to test what I’ve said and to learn how to make necessary corrections.
The 40D which I’m currently using has three metering patters: spot, center-weighted, and the entire frame. For this exercise I set the metering pattern to center-weighted, pointed a bulb at a large very white box of printing paper, put a hinge in the center to focus on and then shot it in the following order:
1) No corrections. The camera does it’s best to make the white box gray.
2) Over-exposed by one-stop. Better, but not quite white.
3) Over-exposed by two stops. That’s white. There is fall-off in the upper right corner but that’s from how the scene is lit (badly).
and 4) I make corrections in Lightroom, including brightening the upper right corner with the gradient tool.
Next up, I’ll do the same thing with a black portfolio case… stay tuned.
Another way to get a good white or black tone is to take a reading from an 18% gray card under the same lighting conditions as you’ll be shooting and just leave the exposure settings there. And yes – they still make gray cards for this purpose.
