Focusing Questions

This weekend, the first warm one this year, I took my 300D and 70-200F4L for their first REAL test runs.

I went to an olmpic diving trial which was a real challenge, but quite fun.
I got much better as the hours went by. However, I discovered that often the camera or lens would not focus where I wanted. I usually set one point for focus, often the center spot. But if I held the camera vertically I set it on the top-center focus point so I would have it over the diver's face.
I had most shots at ISO1600, shutter at 1/250-1/400, and aperture at F4.
I attributed much of the problems to the speed of the divers, although some of the shots were of the divers stationery on the board.

Diving

Yesterday I was shooting some Irish dancers at a street fair.
Again, I used the same focus method as above, focusing on the face, usually half pressing, and following the subject, then full press when I was satisfied with the composition (usually 1-3 second half press).

Upon looking at the pictures, again many did not seem to focus where I wanted.
I've done a few focus tests on real life objects, like a cobbled street at 45 degree angle, and usually focus seems spot on. Could my method be flawed, or possibly a problem relying on the Rebel's AI Focus mode.

Here is one example at 100% crop. You tell me where you think the focus was...

ISO800 - F4 - 135mm - 1/800sec

I do not want to be one saying it's the equipment, when it could very well be the operator but I would say only about 20% focused exactly where I wanted.

TIA

Here is one (50% crop) of the better shots, focused on the face.
However, to me the bottle seems to be even sharper than the face.

ISO200 - F4 - 200mm - 1/1000sec

Drisley,

I was hoping others would respond to your post. I don't have enough experience to add anything but speculation.

Some general thoughts:

- The Rebel/10D can be very frustrating with moving subjects that don't have constant velocity (or acceleration). That covers what I mostly shoot - basketball - and certainly would include the diving event you covered.

- I don't see how any camera could accurately autofocus on a spinning subject (your rotating divers).

- I frequently see my camera focusing on something in the background when it can't lock on the subject. Sometimes that's me, not the camera. A good number of your shots are focused on the background.

- I use AI Servo. I believe the DRebel only has AI Focus - that is, it switches to AI servo when it detects motion in a subject. I don't know if this works better, worse, or the same as AI Servo.

- Sometimes I can't tell whether a bad capture is caused by out-of-focus, camera shake, or subject motion. But I think many of your shots have excess subject motion. Your shutter speeds are quite slow for stopping action (I realize you were max'd out on ISO and aperture).

- The 1D MkI/MkII were designed for sports and apparently excels in the situations that are frustrating you and me. Pro photographers would probably laugh watching us struggle.

- A couple of your shots defy explanation - like the one in your second posting. Are you sure you switched the focus point back to center?

I could go on. I post this mainly to bump your post and encourage others to lend their expertise or add to the speculation.

Thanks for your reply.

Yes, I agree focusing on moving subjects with the Rebel can be frustrating. I would assume that the 10D would be much better since it uses selectable AI Servo mode. No?
I accepted any problems with focusing on the divers in mid air as they are moving very fast. However, I think I did get some decent shots all things considered. I was more concerned with a few of the shots of the divers when they were standing on the platform in which the clock and crowd behind them seemed to be in better focus.

However, even more concerning was the number of out of focus shots I got from the Irish dancers. I assumed after shooting divers on a fast/short 3M board, Irish dancers would be no problem. I actually had more throw aways this time than with the divers.

Here is an image from BB showing the exact focus point on the second shot. Does this seem right?
Focus point

Here is another example shot with the 70-200F4L at 1/1600sec F4

Focus Point

HTTP response: 404 | MIME changed to 'text/html' | Byte size: ZERO

100% Crop

I've had similar problems with focusing on the DRebel. I attributed much of it to the kit lens, although I do have a 28-85 Canon which still frustrated me with the focusing. However, after getting an adapter for my olympus lenses, I took similar comparison shots. However, the Olympus lenses allowed me to close the lens down a few f-stops which in creased the focus. Switching back to the Canon lenses, increasing the ISO and closeing down the lens a bit improved the focus immensely. A little more depth of field is what my lenses needed. Since you're shooting these at an f-4, you may want to try settings f8 or f11. However, there is a trade off with the added noise to take into consideration.

Thanks for the reply.
I shoot a LOT in ISO800 and now ISO1600, and the noise if very minimal if properly exposed, so I dont mind that at all.

I just did some testing of objects around my apartment, like bottles lined up at 45 deg angles, etc, and the focus seems fine.

Again, this may have something to do with limitations of the Rebel itself, as well as yours truly.

If that hacked firmware eventually gets AI Servo working, that should hopefully help alot!

drisley wrote:
However, even more concerning was the number of out of focus shots I got from the Irish dancers. I assumed after shooting divers on a fast/short 3M board, Irish dancers would be no problem. I actually had more throw aways this time than with the divers.
Focus point

I'm always surprised how fast moving are subjects who are dancing, acting, etc. The movement might bring them out-of-focus, might cause blur, or might do both. On the image you posted of the dancer, note that the head is more blurred than the torso, which suggests more of a subject movement than focus problem.

BTW -- I agree. Your Olympic diving shots were terrific. Are you ready for Athens.

Thanks maderito.

I may have thought about motion blur, but since the shot was taken at 1/1600 sec I highly doubt it, dont you? And actually even her dress is quite blurry at full crop. The closest thing I can find to being in focus is the guy's blue sash on the left.

BTw, I'm in olympic photographer training classes at the moment. Lift heavy lens, pound down a few donuts, lift heavy lens, a few pizza slices....