I photograph a lot of running dogs and often experience the same OOF photos when reviewing my images. It occurs when the dog is moving towards the camera and looks as if the AF is trying to focus on the face and the dog runs forward a few inches by the time the shutter fires. I have included some examples with EXIF data. I have micro adjusted the camera/lens used (Sigma 120-300 f2.8 OS) and get sharp images on stationary subjects. Is this just a limitation of the lens or is there any solution to this issue?
Help advice please - Canon 70d AF (AI SERVO)
- Thread starter martinslade
- Start date
Hi Martin,
I was looking at the data and you were using Zone AF. In the manual on page 106, in the explanation, it says that Zone is effective for moving subjects. However, since it is inclined to focus on the nearest subject, focusing on a specific target is harder than with Single Point AF.
That may be the reason.
I try to stay out of the "nearest subject" zones with my 7DII. They seem to be mainly for singling the nearest in a group. At least that's my understanding.
Good luck. I hope this helps.
Macoose
I was looking at the data and you were using Zone AF. In the manual on page 106, in the explanation, it says that Zone is effective for moving subjects. However, since it is inclined to focus on the nearest subject, focusing on a specific target is harder than with Single Point AF.
That may be the reason.
I try to stay out of the "nearest subject" zones with my 7DII. They seem to be mainly for singling the nearest in a group. At least that's my understanding.
Good luck. I hope this helps.
Macoose
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Hi Martin.
It seems like the AF should have been ok, the camera is saying that there is enough dof for the nose and ear to be in focus, as indicated by the active focus boxes, so why the eye and face should be as soft is strange, did you AFMA at or about the distance you are shooting, or at a much different distance?
As far as your suggestion about the movement, that is the purpose of AIServo, it is supposed to anticipate the point the subject will be at when the shutter actually opens, some fraction of a second after the shutter button is pressed. Did you have the shutter button half down (or hold AF on button) whilst tracking your dog, this gives time for the system to acquire focus and determine direction and speed of travel, or did you track your dog without half pressing the shutter button, then press the button fully in one action effectively making AIServo in to one shot AF, this might explain the missed focus.
Cheers, Graham.
It seems like the AF should have been ok, the camera is saying that there is enough dof for the nose and ear to be in focus, as indicated by the active focus boxes, so why the eye and face should be as soft is strange, did you AFMA at or about the distance you are shooting, or at a much different distance?
As far as your suggestion about the movement, that is the purpose of AIServo, it is supposed to anticipate the point the subject will be at when the shutter actually opens, some fraction of a second after the shutter button is pressed. Did you have the shutter button half down (or hold AF on button) whilst tracking your dog, this gives time for the system to acquire focus and determine direction and speed of travel, or did you track your dog without half pressing the shutter button, then press the button fully in one action effectively making AIServo in to one shot AF, this might explain the missed focus.
Cheers, Graham.
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Thanks for your replies. I have also found this a confusing issue. Yes, I have AFMA at typical distances and all is ok and AF has been active for previous frames usually for a few seconds so it has time to track.
It's as if the AF is focusing on the dogs back covered by the AF point in the far left of the zone (group of 4 AF points) and not the highlighted AF points.
Maybe I need to go to single point AF.
Thanks again for taking the time to consider this issue and for your suggestions...
It's as if the AF is focusing on the dogs back covered by the AF point in the far left of the zone (group of 4 AF points) and not the highlighted AF points.
Maybe I need to go to single point AF.
Thanks again for taking the time to consider this issue and for your suggestions...
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I have the exact same issue when I use zone af with my 7DII - it appears to be focusing where I want it in the view finder, but the spot is behind where I want it when they are coming toward me.
When I use single point AF (not spot point AF) this issue doesn't happen and I get tack sharp.
I'm pretty sure this is some sort of user error on my part, others get zone af to work just fine..(BIF for example) so I presume it is me. But I do get tack sharp when I use single point AF method, so I stick with it.
When I use single point AF (not spot point AF) this issue doesn't happen and I get tack sharp.
I'm pretty sure this is some sort of user error on my part, others get zone af to work just fine..(BIF for example) so I presume it is me. But I do get tack sharp when I use single point AF method, so I stick with it.
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There are many possibilities. The 70D is not a super fast focusing camera, and when paired with a third party lens, it might be slower than with a canon lens. This can account for the issue.
A subject rapidly moving toward a camera really stresses the AF system, its going to be difficult with a 70D. Cameras like the 7D MK II have more sophisticated tracking that is better able to estimate where the subject will be when the shutter closes, and actually changes the AF point to where the subject will be.
Set your aperture to f/8 or f/11 for a little more depth of field. That may be just enough to put it in better focus.
A subject rapidly moving toward a camera really stresses the AF system, its going to be difficult with a 70D. Cameras like the 7D MK II have more sophisticated tracking that is better able to estimate where the subject will be when the shutter closes, and actually changes the AF point to where the subject will be.
Set your aperture to f/8 or f/11 for a little more depth of field. That may be just enough to put it in better focus.
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I think your problem is the limitations of AI servo. It works better for horizontally moving subjects. Set your 70D to back button focus and high speed contiuos shooting. 7 frames per second. I use centre point zone focus on my 7D.
Not all my pics are in focus. But I usually get one or two keepers. I took over 100 pics of a hummingbird flying around a fucshia plant going from flower to flower. I took so many pics my buffer was starting to fill up. I took lots of breaks and watched the red light on the back of the camera till it went out and I would take more pics. Good luck!
Not all my pics are in focus. But I usually get one or two keepers. I took over 100 pics of a hummingbird flying around a fucshia plant going from flower to flower. I took so many pics my buffer was starting to fill up. I took lots of breaks and watched the red light on the back of the camera till it went out and I would take more pics. Good luck!
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