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Hi everyone,

Can someone educate me, in what condition is that button become useful . I never used it in my photography. BTW i am using a Nikon D40x. Thanks

I have mine set to lock exposure only ( AE-L) and use it in conjunction with spot metering when I am not comfortable to rely on matrix metering. Allows you to select part of a scene for metering (say 18%) grey equivalent and then lock in and recompose.

Have you consulted the Nikon manual first? There's lots of info there...

You can either set it to lock your exposure or focus.

Useful when you are under tricky light conditions where you move a little bit can cause serious exposure and/or focus problems.

This button eliminates this by adjusting focus and/or exposure before you half press the shutter.

Appropriate technique and practice is needed before you get any advantage out of this feature.

One of the best uses for this button is to set it up as the AF-On button. Set it up in the Custom Menu to the AF-On Setting and then use this button every time you want to focus the camera (instead of pushing the shutter release to focus). The advantage with this way of working is that it separates the AF actuation from the shutter actuation and it means that you can pre-focus and then push the shutter release in the knowledge that the AF won't hunt at the moment you want to take a photo. It is the preferred way of working for many serious photographers.

Good thread I was looking at this stuff last night online and didn't know really what it was about. now i'm 50% more sure now

Antsl wrote:One of the best uses for this button is to set it up as the AF-On button. Set it up in the Custom Menu to the AF-On Setting and then use this button every time you want to focus the camera (instead of pushing the shutter release to focus). The advantage with this way of working is that it separates the AF actuation from the shutter actuation and it means that you can pre-focus and then push the shutter release in the knowledge that the AF won't hunt at the moment you want to take a photo. It is the preferred way of working for many serious photographers.

thanks for the response, Antsl's comment makes a lot of sense to me. Thanks again for everyone input and teaching.