Originally posted by shuy i understand that for a normal camera, u must press halfway to focus first b4 pressing it all the way. what happens if i press it directly all the way down? i'm using a 3100Z btw.
On most cameras, half-pressing the shutter release button engages the auto-focus and/or auto-exposure, after which the only remaining thing left to do is to actually open the shutter for the exposure. So that'll shorten the time required after you subsequently fully depress the button. More importantly, you can recompose your image after initially focusing on and exposing for your subject.
On the other hand, if you immediately press the shutter button all the way down, all these tasks will still have to be performed, but they will be done together.
So it's not really true that half-pressing the button will "save" time--the same amount of time is still taken to perform all the necessary tasks, but half-pressing separates the more time-consuming tasks from the actual exposure. Obviously, if you have time to compose your shot deliberately, it's better to stick with half-pressing, but for action shots you'll probably just want to press the shutter button immediately and be done with it. Better still, use manual focus and manual exposure settings, and you don't even have to bother about this distinction at all.
Pressing all the way down is ok but it depends on how you do it. If you "snap" the button, there's likely to be camera shake. It's better to squeeze the button slowly to get a clearer picture. That is why some people prefer to use the halfway-down method.
Some users have made use of the longer delay that occur in the full-press scenario to reduce camera shake. So it's doing the full-press and release, hold your breath, hold still, and let the camera finish the task.
This technique only works with slow AF cameras (common in DCs)
hmm, i sometimes press halfway at auto exposure to check what exposure settings my cam has detected. then if i want, i change abit here and there to my liking. i guess that's my biggest advantage of halfway pressing.