40D and setting exposure

I spend most of my time in Aperture mode on my 40d. I can't figure out how to basically set the exposure based on one thing I point at, then focus on another. My exposure seems to be constantly changing from moment to moment based on what I'm pointing at. Any help on how to do this?

I don't think you can do this with aperture. What you are doing is basically like shooting in M. Have you tried using full manual? I was in your shoes up to about a month ago and I basically shoot only full manual now.

Either you need to start shooting in manual in that situation, or you need to move the metering function to a separate button so you could meter, then hold that setting recompose and focus.

I'm not sure about the 40D, but my XSi lets me freeze the metering and hold that exposure while I recompose my shot.

However, I find manual to be easier than changing the way my buttons function.

You can set the shutter to lock the exposure on the 1/2 press if you wish. I don't remember the function for that but that's how I had C1 set up (Av) when I had a 40D. Regular Av was setup as you describe but sometimes I needed it to work the other way so I would switch to C1.

I think that you may want to try the AE lock Its the * button. More info can be found on PG 95 of the manual.

Since I had the focus on the AF-ON button that was not workable for me, especially with a lens that has IS or when in AI Servo. It might be for the OP.

hey actually you can do this.
that is how i shoot.
Im in AV mode
in the custom function mention you can decouple the focus and exposure from the shutter button, such that AF is only triggered by the AF-On button. Once you focus, you can move the center AF point to wahtever you want to expose for, then half press, then re-compose.

OR (which is the more inuitave way) is to use the * for what you want to expose for, then focus on your object with AF-ON, then pressure the shutter...note you have to do this within a certain time other wise the exposure lock with reset itself

if you need help with this let me know//its getting late

subnet_rx wrote in post #8354019
I spend most of my time in Aperture mode on my 40d. I can't figure out how to basically set the exposure based on one thing I point at, then focus on another. My exposure seems to be constantly changing from moment to moment based on what I'm pointing at. Any help on how to do this?

As the above advice shows, there are several different ways to do it. If you don't want to set custom functions and put AF on the AF-ON button, just use the * (Exposure Lock) button....point at what you want to meter off of, push the * button to lock your exposure there, then recompose your shot and proceed as normal. If you did it correctly, a * will appear on the lower left of your viewfinder, indicating Exposure Lock.

Another way of doing this is by setting the power button to one switch above "on". Press halfway on the shutter button then exposure button same time and move the dial. This should set the exposure. Annoying yes, but manual is the easiest way.

How long does the exposure lock remain once you press the * button

I'd just put it in manual, find the shutter speed that puts the meter at 0 and then move the camera to refocus. Seems simpler than changing the custom function each time.

amazon wrote in post #8394605
How long does the exposure lock remain once you press the * button

Something like 6 seconds but I don't recall. I just programmed the shutter to AE lock on the 1/2 press and the back button to AF focus ON. Seemed more
"natural" to me and no need to ever change the settings. If I wanted to meter at instant of taking the shot I just pressed the shutter all the way, not stopping at the 1/2 press. If I wanted to lock the exposure and shift the framing, for example, 1/2 press, shift camera, trip shutter. Just seemed more intuitive and since the settings are permanent, easier to not have to think about what you are doing.

I hate having to think what I'm doing, I don't really the equipment for that sort of thing