"Malcolm Stewart" <[EMAIL PROTECTED]> wrote/replied to: >Fascinating! >Two experienced photographers stating opposites about the same lens' AF speed. >I too have noticed that my (old) EF 85 f1.8 seems relatively sluggish in >comparison with my EF 100 f2.8 USM (over comparable ranges). Others have found >just the opposite. I wonder if USM motors gradually gather (very) fine dust as >they age, and whether this has a long term effect on AF speed? > >Some years ago, I met a golfing photo pro who had found his USM lenses had got >gummed up by fine sand when he was shooting a tournament in the Gulf States. >Since then Canon have improved the sealing on their premium bodies and lenses. >Just a thought...
I think it depends on the type of shooting you do, the ranges of focus you are working in, etc. I also noticed it depends on battery condition. When my battery's getting low, focus is a bit slower. If I compare, my 85/1.8 is very fast focusing, but not as fast as the 50/1.4. Smaller lenses for one thing, different mechanisms. The 100-400L IS does have more mass to move around. I would assume it has a larger motor for the task. Here's an example of what I mean by fast focusing: I'm shooting a small bird in some dried winter marsh grass. He's jumping and moving around through the tall brown grass, and I'm trying to focus on him when he's in an open area. He's about 30 feet from me. I'm using centre focus point with the 100-400 at 400mm. It's bright early morning light, and a fairly contrasty situation. It's easy to have the focus pop out when the bird moves behind some grass stalk. My focus instantly goes to minimum. Release shutter button half press and refocus on bird now in open. Zap, instant lock on. Could a lens focus faster? Yes, I suppose, but for many instances, this lens amazes me with it's quickness. I have also heard this from other photographers. If it matters, my lens is about a year old, and well taken care of. -- Jim Davis Nature Photography http://jimdavis.oberro.com Replies in plain text only please! * **** ******* *********************************************************** * For list instructions, including unsubscribe, see: * http://www.a1.nl/phomepag/markerink/eos_list.htm ***********************************************************
