Back Button Auto Focus with Nikon DSLR (D90)

This post has been moved to my brand new blog www.nerphy.com!

During my last trip to Brittany and Normandy, I started using the "Back Button Focus" technique: I used the "AE/AF-lock button" of my Nikon D90 ("AF-On" button on better Nikon body ) to auto-focus instead of the shutter release button!

It's quite odd in the beginning, but now I can't live without it :)

There are three main reason for using this technique:

1. Easily switch between continuous-servo AF (AF-C) mode and  single-servo (AF-S) mode without changing camera settings: setting the camera to AF-C, you can keep the button pressed to have  continuous auto focus or you can press the button to focus and release it to recompose the shot! 
2. Save Battery: the VR of your lens is activated only when you press the shutter release button, saving your battery while focusing
3. It's cool!

In the photo above you can barely see my right thumb using the AF-On button to focus the gull against Etretat cliffs: press to focus, release it to recompose and then shoot! if it would fly away, I could keep the button pressed and start tracking it!

If you want to try, follow this steps:

1. Nikon D90 doesn't have the AF-On button.  So, using f4  setting,  you have to set up the AE/AF-lock button to act as the AF-On button
2. Set the camera’s Auto Focus to Continuous servo mode  (AF-C). This part is what I missed when I first tried this technique some months ago: I used AF-S instead. With AF-S, if you don't keep pressed the AF-On button, the camera will not fire!

If you have a D90 you are done . If you have a better camera, like a D3S there are some more settings:

1. Set the a1 setting (Continuous Release Mode) to Release Priority 
2. Find the custom setting for AF Activation (a5 on the D3s) and set it to AF-On Only. 

This is the video the really opened my mind on this technique:

And here you can see the result, that I posted also on Google+, feel free to leave a comment there :) 

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