Confused on 580EX Zoom Settings

One thing I can't comprehend about the 580EX zoom settings is that how would I know what zoom setting I have to set it? The manual says, "The flash coverage can be set to match the lens focal length from 24mm to 105mm". I have a 24-105 lens, do I have to set it at 24mm or 105mm? Or do I have to set it by what it says on the lens zoom readout like for example I am at 70mm, do I have to set the flash zoom to 70mm? Hey what about lenses like 70-200 which are not covered by the flash range which is 24mm to 105mm only? How do you handle that? any help is much appreciated. thanks guys.

If it's on auto it will zoom automatically. If you're bouncing it won't zoom.

How do you know it's on auto you ask? There is no "M" next to the focal length on the LCD.

I guess I didn't make myself clear. Let's say I am using manual mode. I set the Flash Zoom to say 24mm. My question is that is this the right settings if I am using 24-105 lens? I mean, how would I kow the right flash zoom settings?

Like I said, let it zoom automatically. And don't worry about it. There's no real reason to not let it on auto zoom when you've got it mounted to the shoe.

i have problem in auto mode. the pics came out kinda dark instead of flash filled.in fact, there's a thread for this 580EX issue here. i just can't find it anymore so i can learn from it. at the time i read the thread, i was not using flash yet so i didn't pay attention to it.

www.photonotes.org/eos​-flash

Sticky: https://photography-on-the.net/forum/showthre​ad.php?t=138907

sgamuk wrote in post #2987502
i have problem in auto mode. the pics came out kinda dark instead of flash filled.in fact, there's a thread for this 580EX issue here.

Many things can cause underexposure problems. If you upload a sample image and give us all the details on camera/flash settings, we can steer you in the right direction.

In the meantime, the links that cdifoto provided are highly recommended.