I shot a wedding last weekend and several of my shots seemed to mis-focus. One particular series with a group of children, I shot at least 15 photos in a row, every single shot ended up being focused on the tree/ bushes behind the kids. I checked my focal point and it was dead center on the little girl holding the baby in every one. Below is one of the photos in question. All were shot at 28mm, f-5, 1/800s handheld. DH thinks I focused and re-composed incorrectly, but I can't imagine that I did this on every photo and am quite sure that I didn't because they are centered shots. Any suggestions? This is driving me nuts. Also all were shot with 1d markIII.
My 1DIII would sometimes do that until the last firmware update (1.2.5). A bright background object with high contrast edges (like those leaves) would seem to pull the AF from the selected sensor to a nearby one. This happened even when I disabled AF assist points in custom functions. The firmware update made this a very rare problem. If you've got 1.2.5 and have disabled assist points, the best you can do is try to find an area of high contrast on your subject (maybe the edge of a tie when faces are this small in the frame and have a detailed background this close behind them).
I doubt there's anything wrong with the lens unless you find a consistent back focus problem.
Photon would know more about the MkIII than I, and he certainly knows the Canon dSLR's, but I had similar problems with my 24-70 after buying it new. It had a far worse OOF rate than my other L zooms, and about drove me nuts. I finally sent it in to Canon, and it was better on return. I swear it still is not as consistent as my 16-35 and 70-200 in AF hit rate, but it is better.
In my case, the focus was not consistently back or fore, just plain not hitting consistently. Fifteen shots in a row, though? Not that bad. I wonder if the sun glare evident in the photo was messing with the AF.
Thanks for the input, I will make sure I have the firmware update and I agree the background was lousy- I was shooting formals the opposite direction and the parents got the kids lined up and said "hurry, shoot now" , they figured it was the only chance they'd get before the kids were uncooperative with 5 out of 8 being age 3 or younger.
I looked back at the other shots from right after the ceremony and quite a few of those seem backfocused as well, but there were also plenty that weren't.
If the tree is perfectly in focus, I doubt it is a case of random lens backfocus. It's got to be the camera choosing the AF point, or your focus-recompose was off abit and the sensor grabbed the contrasty tree instead of the kid
Do you have a full res sample of the above image? Looks a bit too small to actually tell where the FP is on my monitor. Also, try shooting a similar scene with your 24-70 mounted on your 40D for a comparison, the results may help narrow the problem down.
Thanks for all the suggestions, I was shooting with the auto focus set on the center focal point, but I think my hubby still had it set to AF assist from doing some sports stuff and I think since the center girls head was small it grabbed the shrubs instead.
With that many shots in a row in question, I think that's the classic 24-70 issue I see in the lens. A bit of distance between me and the subject on the wider fls, and it will most often yield the results you got. A little manual adjustment after focus acquisition helped, and also the much mentioned parfocal method helps tons, which was a natural movement for me when I use the 24-70. I had mine calibrated many times until it finally got it right.
garyvot wrote:
It helps you focus... with your eye.
Does it have some sort of magnification or something in ring in the middle? I don't know much about these things and always looking for ways to better things.
Some have commented that after servicing their 24-70L it came back parfocal.
I would always assume there is a tolerance to it's "parfocalness." Experiment, but don't be
surprised if you get better results using AF at the specific shooting focal length.
? This is driving me nuts. Also all were shot with 1d markIII.