How does AE lock work?

[Wavy C]

What is the correct way to use AE lock on the canon 20d?

Say I move in close to take a reading from someone's face, press the * button and then move back to recompose and take the shot. The exposure lock only holds for a few seconds. After recomposing and half pressing the shutter the camera takes a new reading (ie the AE lock value is lost). Is there a way to hold AE lock until the next picture is taken, or do I just have to keep pressing the * button.

On my olympus 5050, when I press AE lock it holds that value until the next picture, if I press twice quickly it will hold the exposure value for multiple shots, and a single press at any other time will release it. This system makes more sense to me.

Another thing I think users should be aware of is that AE lock on the canon works in a different way depending on the drive and metering modes you are using. If using evaluative metering and single shot drive mode, it will measure the exposure at the focus point. If you are in servo focus mode, it think it always locks the exposure at the centre focus point regardless of metering mode.

[scottbergerphoto]

In my opinion the best way to do AE lock is to use partial metering, put the camera in Manual Mode, fill the partial metering circle with the area you won't to expose for and set the f stop and shutter speed. It will stay on those settings till you change them.

Alternatively,in Single Shot, use CFn.4-1 which separates focus from exposure. Push the * button to focus on your subject. Then release the * button. The focus will not change as long as your subject is stationary. Point the camera at the area you want to expose for, lock exposure by 1/2 depressing the shutter button and recompose while keeping the shutter button 1/2 depressed. Fully depress the shutter button to take the picture.

In AI Servo, exposure is locked at the time of shutter release and not when you half depress the shutter button.
Scott

[Wavy C]

Hi Scott, tnx for replying.

I guess your advice about setting the camera to manual mode is the way to go. AE lock is a feature I use quite a lot so am keen to find the best way of doing so on my new camera. Can't help but think it is a pity canon didn't implement the AE lock in a similar way to olympus - so much easier and available in any mode.

I've also looked at your suggestion about using a custom function to change the focusing, but think I find manual mode simpler than using a button other than the shutter release to focus.

best regards

[picnic]

Scott---not sure I understand here. If you are using M you don't need AEL---the settings are the 'lock' for the exposure and you don't need to lock on anything. If you are using Av, Tv, or P---then I would use the AEL exactly as you stated.

Using Cf.N. 4-1 is my preference. I like to shoot in Av primarily but do want the exposure as I want it--not the camera. I tend to meter on slightly lighter than 18% gray so as not to blow the highlights and lock in with 1/2 click of shutter. Then I lock AF with the * button, compose and shoot.

I don't use AI Servo so can't comment

Diane B

In my opinion the best way to do AE lock is to use partial metering, put the camera in Manual Mode, fill the partial metering circle with the area you won't to expose for and set the f stop and shutter speed. It will stay on those settings till you change them.

Alternatively,in Single Shot, use CFn.4-1 which separates focus from exposure. Push the * button to focus on your subject. Then release the * button. The focus will not change as long as your subject is stationary. Point the camera at the area you want to expose for, lock exposure by 1/2 depressing the shutter button and recompose while keeping the shutter button 1/2 depressed. Fully depress the shutter button to take the picture.


In AI Servo, exposure is locked at the time of shutter release and not when you half depress the shutter button.

Scott

[scottbergerphoto]

Scott---not sure I understand here. If you are using M you don't need AEL---the settings are the 'lock' for the exposure and you don't need to lock on anything.
Diane B
My point exactly! You don't need the AEL and you don't worry about it timing out.
Scott