Evaluative metering and live view
As I mentioned in the metering section, the EOS 550D’s evaluative metering is linked to the selected AF point and this can impact upon the exposure of the image. I composed these images in the LCD screen with the camera on a tripod to ensure that the view remained constant, and, as I’ve found before, the exposure changed depending upon whether the selected AF point was over a white or a black area. However, the exposure also changes when the camera is set to manual focus in Live View.
I took this sequence of shots with the focus set manually on the spout of the black teapot. After focus was achieved I moved the Live View magnification box between the white and the black pots, and although neither the focus nor the scene was changed, the camera adjusted the exposure as soon as the shutter-release button was half depressed. This needn’t be a problem provided the user is aware of it, and a quick ‘in and out’ with a grey card could ensure perfect exposure. I got the best result by increasing the exposure suggested when the magnification box was over the white teapot by 1.33EV.
