AF/AE lock question.

[FishyFish]

Are there any disadvantages in having both AF and AE lock assigned together? I have AF lock switched on on a back button, but not AE lock. This hasn’t been an issue as I’ve tended to select a focus point on my subject, rather than focussing and re-composing, so the camera focuses and exposes correctly anyway, but I’m wondering if I’m missing out on something by not having both assigned?

I guess panoramas would be something that would benefit.

Thanks.

 

[Major Eazy]

Well, the disadvantage is that it will lock both the focus and the exposure settings, which would not always be suitable for some subjects. What if you want to lock the exposure but not the focus? What if you want to lock the focus but not the exposure? The disadvantage is that it will always lock both of them, even if you only wanted one or other.

 

[Asha]

On the odd occasions that I've used the AE/AF function, it's only ever been for the AE

I can't say that I've found a need to AF lock tbh, by contrast AE lock has been very handy at times especially in high contrast situations.

Never have I had both settings set to lock at the same time.

 

[troutfisher]

Correct me if I am wrong but is that not what half press of the shutter button does as default?

 

[FishyFish]

Correct me if I am wrong but is that not what half press of the shutter button does as default?

You have to keep the shutter button half depressed to maintain the lock. If you release it it will reset. Using back button focus allows you to keep the lock even if you release the button.

 

[Asha]

Correct me if I am wrong but is that not what half press of the shutter button does as default?

AFAIK you are correct yes.
Sometimes though the additional AE/AF function can be of great help.
For example, set at AE only, if the subject is focussed upon and locked using the half depressed shutter, the exposure can sometimes be miles out due to the metering being confused by backlight, skies or other stray light sources.
Obviously this can render the subject incorrecly exposed.
By locking the exposure using the AE lock button, then using the shutter release to lock the focus, both settings are as the photographer wants them.

 

[troutfisher]

You have to keep the shutter button half depressed to maintain the lock. If you release it it will reset. Using back button focus allows you to keep the lock even if you release the button.

I know that, I always use BBF on my Canon and frequently AE lock ( meter off the grass-its near enough to 18% grey) but I could not see the reason for having AE/AF lock assigned to one button as that is what the shutter half press does, unless you want to meter and or focus on something else in the shot in which case you need one or the other but I suspect very rarely both at the same time.