Originally Posted by
Alan Lillich
Jay,
Here are usage examples of why I prefer back button focus. This is all personal preference, you may feel differently.
An interesting discussion; I have made my comments within the quote; I am intentionally playing devil's advocate.
1. Leave the body in AI Servo all the time. No need to remember to switch for different situations.
When you say leave it in AIS all of the time, don't you really mean for subjects are that are either moving or have the potential to move during the shoot?
You would not use AIS for landscape or people photos, would you? Wouldn't you change to One Shot?
2. Other than the HH-heavy-gear-BIF case mentioned above, it is a lot easier for me to "mash" the back button than gently half press the shutter button. I know when I'm focusing and when I'm not. I don't have problems accidentally shooting too early. This is true also on a tripod with even the heaviest gear.
I do not "work" on a tripod for moving subjects; only HH either with 70-200 or 300.
When you do HH you have to go into the various menus and make the changes to cancel back button; then you have to do it again to go back to rear focus. Have you programed C1, C2, etc?
If you use the bump method I do not believe you really "mash" the back button because it too needs to be tapped gently to "bump". I haven't tried it but I am guessing bumping the larger shutter button might be easier than bumping the small back button.
2.1. My goal for HH-heavy-gear-BIF is to improve my thumb coordination. It isn't massively bad, just slightly less comfortable and more tiring to use my thumb for several hours. Note that a 70-200 is light enough to use my thumb, as is a 400 DO, and probably a 300 f/2.8. The Nikon 200-400 is 7.4 lbs, 1.4 lbs more than the current (not v II) Canon 300 f/2.8, 3.1 lbs more than a 400 DO.
3. When I want to focus and recompose I simply press the back button, let go, recompose, shoot. This uses 1 button to focus, press it again to change focus. Using shutter plus AF lock you have to press 2 buttons each time, and you have to press AF lock while holding the shutter at half press and not accidentally shooting. And then all the confusion/accidents when the AF lock releases when you don't expect it.
Yes, you do use two buttons when using AF-ON as AF-OFF. However, if I am shooting a bird that has stopped for a moment, it is my understanding that when you push the AF-OFF button the focus at the moment you push the button is locked and you simply recompose and shoot. If the bird starts to fly away you simply let up on the AF-ON button and AIS automatically starts.
Alan