View source for Back button autofocus

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This is a trick I learned from  [https://backcountrygallery.com/free-back-button-af-guide-for-nikon a guide by Steve Perry]. See his guide for more details. I was skeptical, I briefly tried it, and I have been using it ever since. 

The only problem I have is that when someone uses my camera they are not able to [[focus]] because they are not used to it. 

===What is it?===
Most digital cameras with autofocus will [[focus]] quickly while you are halfway pressing down on the shutter. In essence every time you are taking a picture, you will focus again. In most cases the camera will do what you want, detect the ''pertinent' part of the picture and focus razor sharp on that while you take the picture. 

In back button autofocus, you assign this autofocus function to another button on your camera (usually on the back, where your thumb can easily reach it, hence the name). This way you can press a button to [[focus]] and keep the camera focussed on your subject. The [[focus]] will not change when you press the shutter button to take a picture (like usual). 

By pressing this new [[focus]] button continuously you can achieve the effect of following the [[focus]] as well. 

===But why?===
There are some challenging situations (trees, grass, children playing) for the camera autofocus system where the camera will ''think'' you want to focus on something else. Since they also focus insanely fast you may not realize that your shots ended up sharp on the grass leaves and not the cute rabbit that was halfway hiding in the grass. 

The back button autofocus simply gives you more control over when to let the autofocus take over. Once you use it, there is actually not much difference or downside to it, that is why, you can keep on using it even if you do not always benefit from it. 

===Should I use it?===
If the problem I am describing does not sound familiar, do not use it. Keep it in the back of your mind, once you start having issues that your autofocus is ''too smart'' for its own good, maybe come back again, and give it a try. 

There are many people who would not really benefit from such a setting. Some ''like me'' that tried it find it more practical to work. 
===How?===
See the excellent [https://backcountrygallery.com/free-back-button-af-guide-for-nikon back button setup guide by Steve Perry]


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