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Old Feb 9, 2004, 8:37 AM   #1
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Hi: My last post on flash quickly outstripped my abilities. I've been reading since then, and used much of that info. It turns out that 1/200th second with flash is indeed able to stop action similar to 1/800th second with the flash in hi speed sync. Good data for me, thanks.

Now I feel that it is focusing off? I've viewed people talk about the seven focus points and finding them in the software. Is this possible? In other words, I set it to focus in the center box, and it often seems to be considerably clearer on the far wall of the pool than the swimmer himself. The distances may be 25ft to the swimmer, and 35ft to the wall. I'm reasonably certain that I see the focus confirmation light up directly over the swimmer's shoulders.

Again, thanks. gary

300D, 18-55mm, 50mm 1.8, 24-70 2.8
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Old Feb 9, 2004, 9:25 AM   #2
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Setting the focus over the swimmer's shoulder may be your problem in that case. Directly over his shoulder would be the space behind him, in this case the wall 10 feet away. Focusing on the eyes will often be your best choice for cases like this.

The camera will return a confirmation that the camera is in focus, but it may well be focused on something other than what you think you're focused on. I always set my camera so that only one of the focus points is active giving me a bit more control over where I intend to focus.
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Old Feb 9, 2004, 12:51 PM   #3
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Quote:
Originally Posted by ohenry
Setting the focus over the swimmer's shoulder may be your problem in that case. Directly over his shoulder would be the space behind him, in this case the wall 10 feet away. Focusing on the eyes will often be your best choice for cases like this.
Good point OHenry... and again this is a key point that I try to bring up before, but some folks are refutting its practice: My experience has been to completely zoom-in to fill the subject with the AF point(s) and back-off.

The active AF area is larger than the red rectangle in the viewfinder. If you only use the red marker(s) in the viewfinder, and its not overcovering the area you try to focus on, you're guaranteed to get back (or front) focus if an area of the active AF element detect something more detailed (or contrast) outside of the red AF outline! Older generation lenses do not have this issue since they kept their focus while zooming...(no AF back then)!

The only problem is with certain newer lenses (especially with the EF 28-135 IS USM), you can't zoom in to focus and back out to compose... The focusing distance varies as you zoom in/out!!! ops:
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Old Feb 9, 2004, 1:43 PM   #4
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That method works fine for zoom lenses but won't work with primes (short of moving yourself in relation to the subject which isn't always an option).

Focusing is such a critical factor and one of the weaknesses of today's cameras that don't offer alternative focusing screens. Good point about the active AF area. I prefer to select ONE AF point rather than allowing the camera to have all 7 available, but even that requires attention as you pointed out.
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Old Feb 11, 2004, 12:08 AM   #5
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NHL,

All Canon zooms (I believe) change focus when zooming. My 70-200L IS does that too. Thus your method doesn't work too well with Canon zoom lenses.

That said, the point about the AF region to be bigger than the rectangle in your viewfinder is a very important one to remember. The simplest way to avoid mistakes is to focus on something that is a bit bigger than the rectangle in the viewfinder. Of course, that is easier said then done with a moving subject :-)

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Old Feb 11, 2004, 5:28 AM   #6
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Barthold

This is a design tradeoff that the lens designers have chosen to keep a zoom compact and light now that they have the camera AF going for them, but it could be done (hey they did it before in their FD's)! Other manufacturers have kept this tradition though, since some of my friend's Nikon and at least two of my Sigma's hold the focus while zooming.

I was appalled when this variable focus first appear on the Minolta Xi zoom lenses. Theses lenses have motorized zooms for their autofocus SLRs which can track a subject while it moved away or closer and kept their composition ratio constant for the shot. It was a design trade-off that I can live with, but now it looks like this has become a general practice (and no motorized zooms to boot):
"In addition, when a Zoom xi Lens is attached to the 9xi, five different APZ (Advanced Program Zoom) programs can be manually selected. All will continuously adjust the focal length so your picture remains well composed at all times." Check the Sport Action 2 and the Child Cards:
http://www.35mm.freeserve.co.uk/mug/card.html

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Old Feb 11, 2004, 10:31 AM   #7
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NHL, I can live with the tradeoff, I think. My 70-200 IS is heavy enough for hand-holding. I know where to aim to focus correctly, and since it is digital I shoot a few extra shots anyway. The weight is one of the main reasons I wouldn't buy the new 28-300L IS, it is even heavier.

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