# Silly question on AF button on my 500mm 4.0 II lens



## daniela (Mar 31, 2016)

Hi Guys!

Slowly I get used with my gear, but I do not know, what to do with the AF stop buttons on the outer ring of the lens? What is it for, and how do I have to use it?

Some advice would be really be welcomed

Daniela


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## neuroanatomist (Mar 31, 2016)

The original point was to temporarily stop AF, useful for sports shooters with one hand on the shutter button in AI Servo, for example when a referee runs in front of the players. More customizable AF settings have somewhat obviated that use. 

If you check Custom Controls (in the manual or just try it), you'll find several functions can be assigned to the LENS button. Personally, I have it set to switch from One Shot to AI Servo.


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