1st Gen 70-200 2.8 IS focus issues

[dcsimages]

I'm having an issue with inconsistant focusing at 2.8 to 4.5. 

I'm doing tight portrait at 200mm, not at the closest focusing distance though and focus point from shot to shot is shifting from dead on to half an inch back or front focused at random. When I look at the focus points in DPP they're just where they should be, but around 30% of the time the focus is just slightly off.

I've just started try to shoot with this shallow a depth of field. I always tried to shoot with this lens in the past around ƒ8 - ƒ11 as that's where it's sharpest, but I'm working on a new shallow depth porfolio.

I'm shooting in single shot, half press shutter button, and picking the closest focus point and setting it on the inner corner of the closer eye.

Would either of the AI modes help? Does tracking help if the subject is moving very slightly back and forth and than across the frame?

Would shooting bursts help?

I've tried back button AF, but all the buttons I could use to start and stop it are awkwarding placed on the camera for my hands.

[dcsimages]

Canon 5D Mark III

Actually 2 of them and the lens exhibits the same behavior with both bodies.

Back button focus allows for taking multiple shots without the camera trying to refocus every time.

I'd use the center point, but I'm trying to capture very fleeting expressions and constantly recomposing doesn't work.

[Waddizzle]

---

@dcsimages wrote:
Canon 5D Mark III

Actually 2 of them and the lens exhibits the same behavior with both bodies.

Back button focus allows for taking multiple shots without the camera trying to refocus every time.

I'd use the center point, but I'm trying to capture very fleeting expressions and constantly recomposing doesn't work.

---

I know [how] BFF works, and why people use it.  I it is good that you checked focus and discovered that it did not improve your results because the problem is not with the lens.  The problem really appears to be user error.

It has been suggested to you that you at least try using just a single AF point, but you have rejected that idea.  I believe your issues are a result of you not fully understanding how the [very complex] AF system works, and the behaviors to expect in different AF modes.

If you are not willing to try what has been suggested, then that leaves only [one] solution for you.  I sugggest that you download a free copy of the full User Guide from Canon.  Please do not reject that advice.  Good luck.

[ebiggs1]

" The problem really appears to be user error. ... because the problem is not with the lens."

I respectively agree, please heed this.

[dcsimages]

So, it's "user error" to expect that a lens focuses consistently while using one of the 61 focus points built into the camera body with an L lens?

I really don't appreciate the condescending attitude.

There is a reason why I don't want to use the center point and recompose every single frame. I'm trying catch very subtle, fleeting expressions in the eyes of the actor as I'm shooting. If I was constantly moving the camera, I'd be missing as many chances to get what I'm looking for as I'm losing to focus issues.

[Waddizzle]

---

@dcsimages wrote:
So, it's "user error" to expect that a lens focuses consistently while using one of the 61 focus points built into the camera body with an L lens?

I really don't appreciate the condescending attitude.

There is a reason why I don't want to use the center point and recompose every single frame. I'm trying catch very subtle, fleeting expressions in the eyes of the actor as I'm shooting. If I was constantly moving the camera, I'd be missing as many chances to get what I'm looking for as I'm losing to focus issues.

---

I thought this was about the lens, not AF points.  It was suggested to you to try a test, in order to check the lens.  You asked for help and categoricailly rejected the idea to test the lens.  

I suggest that you contact Canon Support, and do follow their suggestions and troubleshooting.  Good luck.  

[dcsimages]

Testing the lens using the center point is useless because I'm not going to shoot with the center point.

I'm shooting vertically and using one of the focus points in the second row down, usually the end one on either side depending on whether the actor is facing slightly right or left.

Camera is on a tripod, although I have the head slightly loose so I cam adjust for the subject moving .

I have sequences of a dozen shots in a row, where the subject hasn't moved, the focus point is on the eye that I want it to be on, and the focus is randomly jumping between forward focus, in focus and back focus.

Before I send the lens in for service, or maybe upgrade to a Mark III, which I wanted to avoid since I might be buying an R5 and R6 when I can get my hands on one, I wanted to see if other people have seen the same behavior or if using a setting other than single point spot focus will help.

[ebiggs1]

"I thought this was about the lens, not AF points"

The answers, suggestions or advice is meant only to help. Nothing more.  It is, still, I believe, you not understanding how the lens and camera work together. A simple test using just the center focus point will tell you if it is the lens or your technique.

If the photos come out consistently OK, you know the answer.  If they do not call Canon. If you don't like our replies call Canon. 1 (800) 652-2666

[ebiggs1]

What I would do is use just the center focus point. Turn all the others off. You are just missing focus plain and simple. No, do not use Ai-servo. It will only make things worse. I seriously doubt you need focus adjustment. I don't know way folks jump to that conclusion so quickly. Most "L" lens do not need it.

Your question implies something in the photo is sharp. The first place to look is mis-focus not it's the lens fault.