Focus Problem!!!!

[shim]

Has anyone had problems with the 20-D focusing in back of your subject?

[J Rabin]

If you use FLR it frequently will result in "apparent backfocus." I.e., focus-lock-recompose technique from 35mm film SLR days, Especially if you're using low f/stops. FLR is finito. Much more infrequent is back focusing lenses, more so with 10D than 20D. But, these you can send for calibration.

[RJSorensen]

Post the shot and lets see . . . mine does, when I aim wrong. These are so quick and fast, that if you lock in on something other than what you 'think' you are on, it has this effect. I went to single, center point to help me with, lol, MY camera problem.

[davidwegs]

Just sending my 2nd 20d in for rear focus. It is about an inch back focusing with 16-35, 17-35, 35, 50, 24-70, 28-75, 85, 100, 70-200 IS. Oddly enough it is not there with my 105 Sigma macro??

Hmm, well its probably not the lenses. :-)

This is the 2nd of three I own that rear focuses by about the same amount. I am fortunate in that I can compare them with other bodies/lense combos.

Had this problem with my first two 300d's a couple of years ago. I guess Iam pretty critical about focus accuracy. I have had a 1D2 and now a 1Ds2 and needless to say, they are practically flawless.

[Kostyanych]

I have this problem sometimes...
And I could not find the reason...
I use centre zone all the time, Single shot mode, but, sometimes I am getting backfocus in several shots in a row.
I did focus test, and it looks like it's Ok.

20D, EF-S 18-55, EF 24-85, EF 35-135.

[pradeep1]

Just sending my 2nd 20d in for rear focus. It is about an inch back focusing with 16-35, 17-35, 35, 50, 24-70, 28-75, 85, 100, 70-200 IS. Oddly enough it is not there with my 105 Sigma macro??

Hmm, well its probably not the lenses. :-)

This is the 2nd of three I own that rear focuses by about the same amount. I am fortunate in that I can compare them with other bodies/lense combos.

Had this problem with my first two 300d's a couple of years ago. I guess Iam pretty critical about focus accuracy. I have had a 1D2 and now a 1Ds2 and needless to say, they are practically flawless.


Was the problem fixed properly after getting it back from service? I am thinking of sending my Rebel XT for service for a front focussing issue.

[spm248]

I have been having this same problem with my 20d. This is with a 70-200mm f2.8L. A basketball player is flying through the air about to slam and it focuses on the fans in the bleachers? what? i am pretty sure this was on servo as well

pisses me off it happened again today

48796

[tim]

I have been having this same problem with my 20d. This is with a 70-200mm f2.8L. A basketball player is flying through the air about to slam and it focuses on the fans in the bleachers? what? i am pretty sure this was on servo as well

pisses me off it happened again today

Use single point focus, rather than letting the camera choose the focus point.

[Jon]

I have been having this same problem with my 20d. This is with a 70-200mm f2.8L. A basketball player is flying through the air about to slam and it focuses on the fans in the bleachers? what? i am pretty sure this was on servo as well

pisses me off it happened again today

If that was full-frame, not a crop, double-check what AF mode you were in, and which focus point(s) were supposed to be active.

[TheSteveMadden]

I have been having this same problem with my 20d. This is with a 70-200mm f2.8L. A basketball player is flying through the air about to slam and it focuses on the fans in the bleachers? what? i am pretty sure this was on servo as well


Two points: Many times the autofocus will choose an area of more contrast over the closest subject if it is within the focus point coverage area. I've seen this on static wildlife shots if sunlight on a thicket behind the subject creates a prime constrasty target even with center focus point selected and the subject dead center, but not completely convering the center focus area.

The second point is that with AI Servo focusing, the first shot is shutter priority, meaning that the camera will take a picture at the time you press the shutter release even if it's not in focus and will not wait for the Servo Focus to do it's predictive magic. If you are set for continuous shooting, the second and subsequent shots will use predictive focus priority, meaning that the lens will pre-focus to where the subject is expected to be at the time of the next shutter release will happen, even if it means delaying the shutter momentarily. If the subject is moving predominantly towards or away from you, the second shot will often have much better focus than the first.

If you know you're specifically going for a slam dunk shot, I would recommend pre-focusing on the backboard or something at the same focal distance as you expect the player to be and not relying on auto-focus.

[cfcRebel]

I have been having this same problem with my 20d. This is with a 70-200mm f2.8L. A basketball player is flying through the air about to slam and it focuses on the fans in the bleachers? what? i am pretty sure this was on servo as well

pisses me off it happened again today

48796Actually 20D is pretty smart you know. It will automatically focus on subject that establishes eye contact with the camera. In your case, the red USC TROJANS dude. :lol: Didn't you read about the new camera technology that disables the shutter if no smile is recognized? This is something similar.