Why not IR Focus Assist Beam with AI Servo?

[EricKonieczny]

What is the reasoning behind not having the IR Auto Focus Assist Beam work while in Ai Servo?

It would be very useful for Low Light moving objects, and for some sports shots, like indoor swimming.

I had my 580 flash on my 20D, but with the custom function 7 turned the flash emit off, to help use the IR auto focus in One Shot.

But when I switched to AI Servo, It was pointless to still use the Flash.

I was at a swim meet yesterday and it got me thinking.

Is this not possible, Cost too much?

[Simon Spiers]

Maybe because if your using these focusing modes ,the object will be moving ie a car ,bird or similar. Considering the beam will unly work a few tens of feet ,beam assist would be next to usless!

[tim]

Plus it could show up in the photos.

[CyberDyneSystems]

Plus it could show up in the photos.
Plus it would be on almost all the time..

[Curtis N]

Plus it would be on almost all the time..Plus it would drain your batteries quickly.

[RDKirk]

Plus it's too slow. Remember that AI Servo is predictive focus--the camera is not trying to focus on where the subject when it takes the "look," it's trying to "lead" the subject like a skeetshooter leading the clay pigeon. If we add a second set of calculations to integrate, it won't be fast enough.

[AXENA]

You know.... that's why this board is great..... I spent the past few hours mulling through the Canon manuals ( HA HA HA AH A)... looking in both actually, 20D and the 580EX to find out if it was the CFn4 that turned off my AF Assist Beam... only to find this thread...

Now I at least know I am not crazy.... and I got my beam back... I've been shooting without it for so long since I am always in AI Servo... and just sort of gave up on the topic, but tonight at a wedding I absolutely needed it.... so what did I do???? I flipped the cam to AUTO then quickly turned the dial to Manual once focus was set and fired.

All of the shots worked because the focus was set witht the AF beam in Auto and I flipped quick enough to maintain the focus in all of the shots. I was dragging the shutter so I didn't want to use AUTO.... silly me... but hey, it worked.

Why doesn't Canon just put this stuff in the manuals??? It would make life so much easier, lol......

Thanks for the thread, and the board!