AE -L button

[wheellathe]

A mate of mine convinced me to set up my D7000 so the AE-L / AF-L works the auto focus mode and the shutter button operates the shutter only. This setup seems to work OK once you get used to it, but now and then the auto focus doesn't operate to focus the camera. Does anyone know why? Thanks

[robcran]

This is a fairly popular technique and it gives you all the focus modes in one hit. It does take a lot of getting used to though. The other drawback is when you are handing your camera to someone who is not familiar with this system - you have to "un-program" it before handing the camera over or you will get out of focus shots.
On my D300 I get an extra button called AF-ON which is used for this purpose. Once configured this way, pressing the AF-ON (or AE-L in your case) gives you single focus if you press and release and continuous focus while you are holding it down. It also allows the 'focus and reframe' technique for off centre subjects.

Now, as to why sometimes it doesn't work on your camera there are only a couple of possibilities if it is set up right in the first place:
1. there is not enough available light, or sufficient contrast, for the AF system to operate at all. You would get an AF failure regardless of how you set up the button
2. maybe there is a problem with the button contacts and it is not operating every time
3. maybe you have the shutter release set to focus priority, in which case the shutter will refuse to operate until exact focus is achieved. This would appear like a failure to focus. I don't know what menu option that is on the D7000, but its a1 and a2 on the D300.

[farmer_rob]

I have my d7000 set that way, but have not had issues with it not focussing on command. I think a bit more information might be needed:

What focus mode (af-s, af-c, af-a) is it set to? (There are differences about when it thinks it needs to focus with the af button held on depending on the mode.)

How many focus points are you using? (I use mainly one focus point, but have had some issues with the camera not finding the desired subject for focus on multiple points.)

What lens? (The kit lens A mode is a bit different to the A/M and M/A modes on the ohter lenses.)

Are there any consistent times when it does not focus on command?

[wheellathe]

Thanks for that, I've tried af-s, af-c, af-a. I would of presumed that it would focus on the same setting as it would using the shutter button.

[I @ M]

Another thought.

Are you using the U1 and U2 custom menu functions and possibly have only set it to AF on the button in one of those menus?

[farmer_rob]

U1 and/or U2 are useful ways of having a setup to enable handling the camera to someone who is unaware of the ae-l button for focus.

[farmer_rob]

Thanks for that, I've tried af-s, af-c, af-a. I would of presumed that it would focus on the same setting as it would using the shutter button.

Reasonable presumtion, but it is hard to do a side-by-side comparison, especially if the camera fails to focus intermittantly. (I hate af-a - I find that it doesn't focus on what I want, when I want it.)