The Canon EOS Digital Rebel XS/1000D Companion

Custom Functions

In Chapter 10, you got a glimpse of the XS's custom functions when I discussed mirror lockup. Custom functions are special commands that you access through the Custom Functions command on the third tool menu. While there are a few commands, such as Mirror lockup, that seem more like primary commands that should be in the normal menu system, the bulk of the custom functions are commands that let you tweak and alter the behavior of other commands.

To alter a custom function, choose custom function (C. Fn) from the third tool menu. Use the left and right arrows to select the function you want to edit; then click Set. You can then use the up and down arrows to change the value of that function. Press Set when you've configured it as you want it. Here's what they do:

01 Exposure Level Increments

This lets you change the increment used by exposure compensation, flash exposure compensation, and auto exposure bracketing. You can choose between a 1/3-stop (the default) or a 1/2-stop. Obviously, a 1/3-stop gives you a finer degree of exposure control, but a 1/2-stop is easier for some people to conceptualize.

02 Flash Sync Speed in Av (Aperture-priority AE) mode

The shutter in the Rebel XS is composed of two curtains. One opens to expose the sensor, while the other closes to obscure the sensor. On very fast shutter speeds, the second shutter starts moving to close off the sensor before the first shutter has completely opened. In other words, the sensor is never fully uncovered. ...