back button focusing questions - after reading past threads

[MichelleK]

I am still trying to understand the back button focusing and I am not "getting" it 100%.

From my search of past threads I put my camera on custom function 4-3. So I press down the star button and it focuses...do i need to half-press the shutter button, does that set the exposure??

I dont really get how this back button focusing is any different than pressing the shutter halfway...what is the difference?? I though I would be able to rotate the dial to change the red dots to a different spot if I wanted to.

Also the focus option al servo or al focus (which I understand rotates between al servo and one shot). On a link to an outside website on one of the threads I read it said that if it is on al servo it will follow your subject, can someone enlighten me a little on that. Does it have to be on al servo or can it be on al focus?? Does it stop following your subject when you let go of the star?? I dont really understand how that works.

I am shooting with 30D, mostly children moving, with 50mm 1.4 and canon 28-128 USM IS.

Thanks, Michelle K

[FIREWALLROB]

Focus with * and set exposure with shutter button.

Shooting this way enables you to LEAVE your camera in Servo (forget one shot).

Keep your finger on the * and the camera will continually focus as in Servo - take it off and it stops (as if one shot). It enables you to set your exposure at the last second and is more accurate. There are really no negatives when you get used to it, and a whole lot of positives if you stick with it.

[FIREWALLROB]

The only thing I will say is if you set the auto off to 1 min, you have to "wake the camera" up first, by pressing the shutter - if this bothers you, set the auto off to a higher amount.

Try it for a month or so, and if you have not seen the benefits go back - people must try it first.

[Titus213]

The downside, if any, is that you lose the ability to do AE lock or FEL since that is controlled with the * button, which is now your focus. The up side is that it separates the focus activity from the exposure. Once your subject is focused it should stay there. Exposure is now all you have to worry about and that happens when you take the picture.

I'm not quite sure how to interpret the function in AI Focus mode which appears to be different if you have selected a single focus point or all focus points.

[MichelleK]

Do you guys have any website links where I can read more about it??

Michelle K

[crn3371]

Here you go, 20 pages, almost 300 posts.
http://photography-on-the.net/forum/...the+%2A+button

[CyberDyneSystems]

Don't use 4-3.. use 4-1 and you will still be able to lock exposure using the half press..
There may be times when 4-3 makes more more sense.. but I would certainly recomend learning with 4-1.

Once you get really dextrous with it, then 4-3 will be forgotten anyway, as you will know to automatically lift your shutter finger up when you want to re-lock exposure rather than use the existing lock.

And read that thread