AE AF Lock

[samsnikon]

I am confused by these.

As I understand AE is a mix of ISO, aperture and shutter speed.

AF is simply auto focus (which the camera does when the button is half way pressed down).

However, on my camera, a Nikon D90, AE AF lock is a big deal and I don't think I have ever used it. And I am not ever sure if I ever would.

So what I am seeking help on is :

1.What is AE AF lock
2. What is it trying to achieve
3. Who does use it and why

thanks
sam

 

[tijuana taxi]

AE lock means the exposure setting is locked even when you meter elsewhere via the shutter button which would normally change the setting

Not surprisingly AF lock does the same, but this time with AF, more commonly known as Back Button focusing and you assign AF to that button rather than the half depress of the shutter button

 

[Bristolian]

It would appear, from previous posts on this subject, that most people use the AE/AF button to lock focus - known as back button focusing. Personally I find operating this button for every shot a bit awkward so prefer to use the shutter release for focusing.

I do, however, use it to lock the exposure on occasions. This enables me to set the exposure for one part of the picture and then recompose allowing me to select which area of the photograph has the best exposure.

It took me a while to appreciate the flexibility this button provides