For the 50D and Baseball
Custom Fucntion layouts, menu options, orders, or wording. The EOS 50D pictured here is a typical example. Note the 'translations' below.
Auto Focus Custom Button Which One?
0: Metering + AF start (note: there’s no slash here)
Factory-default setting. You activate camera’s meter and AF by pressing shutter button half-way down. Rear AF-ON button also does same if it’s pressed, so you don’t get the benefits of removing AF activation from the shutter button when this option is set.
1: Metering + AF start / AF stop
AF is still at shutter button. Pressing the rear button will actually LOCK the focus; potentially useful if you shoot a lot of moving subjects in AI Servo AF and prefer to activate AF with a conventional half-press of shutter button. Focus is unlocked by removing thumb from back-button.
2: Metering start / Meter + AF start
Back-button AF activation. Shutter button no longer activates AF, but of course fires the shutter. Metering is continuously updated — if you shoot a sequence of pictures, the camera takes a fresh meter reading for each one. There’s no locking of exposure, unless you separately press the AE Lock button (this last item is not possible on some EOS models).
3: AE Lock / Metering + AF start
Back-button AF activation. Difference between this setting and option 2 directly above is that when you press the shutter button half-way, your exposure is locked and won’t change until you pull your finger off the button entirely. Thus, if you shoot a sequence of pictures in any auto exposure mode, the exposure setting used for the first shot is used for each subsequent shot. Can be useful if you were using back-button AF to easily lock focus and shoot a series of portraits, where you wouldn’t expect lighting to change.
4: Metering + AF start / Disable
Similar to setting “0” above, but now, the camera’s rear AF-ON button is disabled. AF activation is at the shutter button. Convenient if you’re worried about accidentally pressing the back-button and don’t want to use back-button AF.