Lock in exposure

Hi I am relatively new to photography and learning ISO, aperture etc.
What does it mean when they say "spot meter, lock the exposure and then recompose". I know what spot meter is but lock the exposure - not sure how to do that. Can someone explain in easy terms. Should i completely be in manual mode?

thanks
Michelle

You should be in M. Since you control all of the settings then you can set the ISO, shutter speed and aperture to what ever you want and the camera won't change them when you recompose.

In AV and TV you can half press the shutter to lock the focus and then recompose. But you have to change the custom function to allow for this. The 40D has the back focus button already. But the other cameras have to set custom function 4 to 1.

I think the (*) button is the default exposure lock. Half press is the focus lock. Double check with your manual to be sure. Check the custom function section.

Depending on your camera there are different ways of locking it in.

The easiest is to shoot in manual, then the camera has no say on the exposure settings.

The 20D, 30D, 40D and 5D can be set so * button on the back works in different ways to control auto focus, or auto exposure, as well as flash auto exposure.
The 1 series cameras offer even more options I believe.

I am not sure on the 3xx series cameras.

The Rebel series is the * button on the upper right (same as 20D/30D/40D/5D I believe). It is a useful tool.

I agree. Here's why: This shows how the subject can affect the exposure & why manual keeps me worry free:
Post #47

Need an exposure crutch?