Focus with Shutter or * [AF ON] button? -READ ME-

cthomas wrote in post #2081931
How do you do this "With autofocus set to AI Servo mode"?

With custom function 4 set to 1 or 3, you press the * button on the back of the camera, let it focus, then release the button.

Click on the {quote} button near the lower right corner of the post you want to quote. The quoted text will appear in the reply box, where you can delete parts of it to include only the text you want to quote.

Curtis N wrote in post #2082137
With custom function 4 set to 1 or 3, you press the * button on the back of the camera, let it focus, then release the button.Click on the {quote} button near the lower right corner of the post you want to quote. The quoted text will appear in the reply box, where you can delete parts of it to include only the text you want to quote.

Don't I need to set the AF mode on my 20D first? What should this be set to. Since 90% of my shooting is Wildlife this sounds something that could really be a help.

cthomas wrote in post #2084490
Don't I need to set the AF mode on my 20D first? What should this be set to.

If you want AI Servo, you need to set the the AF mode on the camera to AI Servo.

Either you're making this more complicated than it needs to be, or I'm missing something in your question.

Curtis N wrote in post #2084644
If you want AI Servo, you need to set the the AF mode on the camera to AI Servo.

Either you're making this more complicated than it needs to be, or I'm missing something in your question.

This is what I'm to do.

From this it looks like he only set the AF once to AI Servo mode. I don't understand how this was done "I was able to enjoy the benefits of both AI Servo AF and One-Shot AF without having to toggle back and forth (by pressing the AF button and turning the main dial)."

He used AI Servo, along with custom function 4-1 or 4-3.

With this configuration, you can use the * button to focus on a stationary subject, then release the * button. At this point, the focus is "locked" and you can recompose or just wait for the shot. The camera won't try to refocus until you hit the * button again.

In other words, custom function 4-1 or 4-3 make One-shot AF unnecessary, because it gives you an easier way to "lock" the focus.

What Curtis said.

The Camera only uses AI servo in the above quote, but you get the same benifit that single shot focus offers (better in fact IMHO as it's more controllable) becuase you can simply let go the * button and continue to shoot. With AI servo in CF#4-0 (focus with shutter button) then you can't focus recompose, as AI servo continues to run while you shoot using the shutter button.

gingerneil wrote in post #2009483
I am keen to try C.Fn 4 when my new 20D arrivs. Just wondering though, what happens when using a remote shutter release ? I assume the focussing will still need to be done with the * button (or manually) ? If so, it would likely be a case of turning back to 'normal' for tripod work....

Yes, with CF#4-1 ypu still need to focus with the * button.

So when using a remote release, there are times that 4-1 will be of huge benifit (when you want to lock in a focus and not have it altered of the scene does)

and there will be times when you will want to reset the camera to cf#4-0 so that the camera WILL re-focus when you press the remote release.

I use both depending on the application.

CyberDyneSystems wrote in post #2085599
What Curtis said.

The Camera only uses AI servo in the above quote, but you get the same benifit that single shot focus offers (better in fact IMHO as it's more controllable) becuase you can simply let go the * button and continue to shoot. With AI servo in CF#4-0 (focus with shutter button) then you can't focus recompose, as AI servo continues to run while you shoot using the shutter button.

Ok. I think the light is starting to turn on. So first you set you the AF mode on the camera to AI Servo. Seccond you set CF#4-3.

A bird flyes by, you press the * button then you let go of the the * button and shoot away. Then he (she) lands in a tree you put the focus point on it's eye and press the * button let go of the the * button and shoot away. I have just used AI servo and One-shot AF. Is this right?

With C.Fn. 4-1 or 4-3, you need to hold down the * button to track a moving target (flying bird) with AI Servo. For a stationary subject (bird in tree), press the * button, let it focus, then release.

Curtis N wrote in post #2085718
With C.Fn. 4-1 or 4-3, you need to hold down the * button to track a moving target (flying bird) with AI Servo. For a stationary subject (bird in tree), press the * button, let it focus, then release.

Hey thanks. That light is really starting to get bright. I wonder how many other people use this set up?

If you change to One-Shot AF by pressing the AF button and turning main dial. Will the * button still be AI Servo?

No.. the * button simply activates whichever AF mode you have allready selected.

At the risk of being redundant,

The AF mode determines how the AF system works.
Custom function 4 determines how you activate the AF system.
Then of course there is a separate method to determine which AF point to use.
All three of these settings work independently. One does not influence the other.

Curtis N wrote in post #2085893
At the risk of being redundant,

The AF mode determines how the AF system works.
Custom function 4 determines how you activate the AF system.
Then of course there is a separate method to determine which AF point to use.
All three of these settings work independently. One does not influence the other.

Redundant! No. Patient. Yes.

Ok. Let me try this again. Custom function 4 determines how you activate the AF system no matter what AF mode you have set.

I will NEVER be go back to using just the shutter button, or so I think. There is just way too much power with the * and joystick in my opinion.

I finally found the light!

I have a question though, I finally tested CF*4 = 1 tonight with AF set to Servo, when you tap the * button to focus, will you still get the same (beep) when it achieve focus? i do the see dot in the lower right corner blinking sometimes, not all the time when i tap *

however, if i change AF to "AF Focus", then I am able to hear the (beep) when it achieve focus.