I have just bought an EOS30 plus a 28-105usm lense. I am VERY pleased with both and am planning to get the 100-300usm (see my earlier posting-thanks for the constructive replies!). I just have one question regarding the lense. When it is switched to AF, the focussing ring still turns. I know this lense is capable of manual overide, so is this what it is supposed to do? This is the first usm I have had so I'm new to this manual overide thing!

-- Sarah Needham (sarah.needham1@orange.net), April 21, 2002

Answers

This is called Full-Time Manual (FTM) and is a Good Thing. It means you can touch up focus after autofocussing without having to switch over to manual focus mode.

-- NK Guy (tela@tela.bc.ca), April 21, 2002.

As Guy mentioned, Full-Time Manual (FTM) allows you to touch up focus after autofocusing without switching to manual focus mode. You may wish to do this if AF locks on to the wrong thing, e.g., nose instead of eyes. To use FTM

1) lock AF on your intended subject 2) keep the shutter button depressed halfway (to maintain the lock) 3) turn the manual AF ring

Previewing compositions with FTM allows you to work without exhausting your batteries due to excessive AF use.

-- Puppy Face (doggieface@aol.com), April 21, 2002.

I'd like to make a slight clarification to Puppy Face's excellent advice. In step two:

"...2) keep the shutter button depressed halfway (to maintain the lock)..."

You hold down the shutter button not necessarily to maintain the focus lock, as in being locked on the subject, but actually so that you don't reactivate the autofocus. Lifting off the shutter button and pressing down again will cause autofocus to start up again. By keeping the shutter button depressed halfway, you can FTM, then fully depress the shutter button to take the picture without re- activating autofocus and possibly mess up what you've manually focused on. That's probably what Puppy Face meant. I'm just more wordy.

-- Peter Phan (pphan01@hotmail.com), April 21, 2002.

Alternatively, with CF 4, manual and auto focus options are separated more. I have not handled an EOS 30, but on the EOS 3, it works like this...

Setting CF 4 to "3" moves AF to the AE lock button, and disables AE lock function.

Now we can break the process (with AutoExposure), into two parts. First focus, either manually by holding shutter button down half- way, and turning focus ring, or automatically by pressing the AE lock button. Then, recompose if necessary, and fire the shutter by pressing the shutter button all the way.

-- Isaac Sibson (isibson@hotmail.com), April 21, 2002.

I found FTM very confusing at first. Perhaps it might help ( or maybe just amuse :-) you to read of my silly mistakes.

• When I manually focussed first, activating the autofocus would undo the manual focus. I now switch to manual focus, or use CF4=2 to preserve the manual focus
• When I autofocussed first, then used FTM, the camera would sometimes detect that the subject was moving and continuous AF. I have to remember to switch to ONE-SHOT AF, or use CF4=1 or 2
• Sometimes, the camera would keep autofocussing, even though I was trying to use FTM. Silly me, I forgot I was using SERVO AF, which is also active in the ACTION mode

  But FTM also allows new techniques not otherwise possible. For instance, see: Almost Trap Focus.
  
  -- Julian Loke (elan7e-owner@yahoogroups.com), April 21, 2002.

Not to mention this silly HTML mistake ;-)

-- Julian Loke (elan7e-owner@yahoogroups.com), April 21, 2002.

Julian, thanks for writing that "Almost Trap Focus" article. I actually used it this weekend, and it's a neat little trick that helped me get the image! Thanks.

-- Peter Phan (pphan01@hotmail.com), April 22, 2002.