100-300 f 4.5-5.6 USM - focus speed - how fast?

My family just got back from a weekend at the beach and I found that my 75-300

f 4.0-5.6 III USM lens is a wonderful tool for getting close to my kids on the

vast beach without having to run as fast as they do. However, I also found

that the focusing leaves a lot to be desired- slow, slow, slow. I missed more

than a few shots because of this and also wound up with more than a few out of

focus shots or poorly framed ones because my kids moved while it was focusing.

I'm thinking of selling it on eBay and upgrading to the 100-300 f 4.5-5.6 USM

if that lens with its "real" USM will actually focus enough faster to make a

difference. I've searched the forums and elsewhere and it sounds like it does,

but I thought I'd ask for some opinions specifically about the focusing.

 

I've also looked at and rejected the various 70-200 L series lens as well as

the 70-300 DO. Although I know that these are optically better, my only

current purpose for this lens is taking photos of my kids on the beach on sunny

days. In that environment, f8-f11 and ISO 200-400 lets me get shutter speeds

of around 400-1000, which is good enough to freeze my kids in action and

prevent camera shake. I'd like nice photos, but they are really just family

photos, so I don't need optical perfection, I just want to capture the moment.

The potential for equipment to be damaged on family vacations is pretty high

and I don't want to worry about the cost if I should slip on a rock- I can

stomach destroying my two-year-old 350D and a $280 lens, but anything more than

that would make me nervous.

 

So- all I really want to know is whether the 100-300's ring USM really makes it

focus enough faster to be worth the upgrade, or should I just save my money and

learn to live with what I've got?

The 100-300/4.5-5.6 USM certainly is faster than the 75-300/4-5.6 USM, since the former has a ring USM and the latter only a micro USM.

 

If it is "enough faster to be worth the upgrade" is hard to tell.

 

Are you sure you loose shots because of slow AF? Have you tried to set AF to Servo (or use the stport program)?

I used to own the 100-300 f 4.5-5.6 USM and, yes, AF rips. It's smokin' 'cause of the ring

USM and, plus, it only has to move a tiny rear element group rather than a larger internal or

front group.

I tested the 70-210/3.5-4.5, based the same lens design, against my 200/2.8 and 100/2. Those two are damn quick. The zoom even better.

100-300 is fine bang-for-bucks, and a pretty good lens on it's own, buy with confidence

Thanks for your suggestions, I think I'll probably go for the 100-300, but I'll give the 75-300 another outing first to see if I can improve.

 

Rainer- thanks for suggesting changing the focusing mode. I'm pretty sure that the problem is the lens, not my technique. I was using "one shot" autofocus and will try switching to servo. But my understanding is that that helps track moving subjects, but doesn't necessarily help with the initial focus, which is where I was having problems. But it's worth a try- I'd rather learn something and save a few hundred bucks than try and solve all of my problems with new equipment.

I swapped my 75-300 for a 100-300 a few years ago for this very reason, and have never regretted it.

 

Now I'm looking at the new 70-300 non-DO (for IS and optical quality) but I'm not looking forward to going back to the cheap mechanicals. Why can't Canon build a lens with the optical quality of the 70-300, but with a ring USM?

The 100-300/USM "ring-type USM drive is very fast..." http://photozone.de/8Reviews/lenses/canon_100300_4556/index.htm

 

AI Servo works best if you activate it prior to getting to the 'money shot' - start tracking BEFORE the real action begins. "The shutter button has two positions. The halfway position activates the autofocus. If you let go the shutter button, you need to focus all over by pressing it halfway again." http://www.canon.co.jp/Imaging/enjoydslr/p_3_010.html