Nikon D90: Focus selector lock VS AE-L/AF-L

[RichardsTPF]

Just get my D90. I am reading the manual on P56,57 and testing with it. I still don't understand what function of the AE-L/AF-L. I tried to search in TPF, didn't find any result.

 

[joealcantar]

Just as the name implies it can do either or both depending on the model of camera , for the most part it is in the menus as to what you want it to do.
Let's say you set it for AE-L (exposure lock) and you go to shoot a subject against a brightly lit window. Depending on your metering mode the camera will take a reading spot/center weighted or Matrix reading, if you take a spot reading of the subject against the brightly lit window and push and hold the AE-L button the camera regardless of where you compose will hold that setting until you release it. So now you compose and focus and take the shot you know the subject will be recorded correctly regardless of the bright background.
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That is just one example of many you can apply it to.
http://www.photoanswers.co.uk/Advice/Search-Results/Techniques/Using-exposure-lock/
Nikon D90 Custom Menu: Controls
Nikon D90 rear controls
Auto Exposure Lock (AE-L) with Nikon D90 | Daily Tips and Tricks for Digital Photography
How to use AE-L/AF-L button correctly | Daily Tips and Tricks for Digital Photography
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Shoot well, Joe
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http://www.shortcourses.com/use/index.html

 

[KmH]

That button can also be configured to be AF-ON. Auto focus is then no longer initiated with a half-press of the shutter button, but by holding the back button down. Which is why setting just about any DSLR camera up that way is known as using back button focus.

 

[RichardsTPF]

Thx.

 

[Kerbouchard]

Mine fires the flash to measure exposure(FV Lock). Used to have it set to AF-ON, but my wife is a blinker so it works better for me to be able to fire the pre-flash and lock in the value.

Like the other's have said, its a customizable button. Set it to what you will use the most.