Canon EF 24-105mm f/4L auto focus expectations

I picked up a Canon EF 24-105 f/4L last year (as an upgrade from my EF 28-135mm f/3.5-5.6). I find that I am continually disappointed by the auto focus results with every shoot with this new lens, even in good outdoor lighting. I can manually focus and get great results, but a shoot using auto focus always results in at least 50% of what I would consider soft focus photos. I sent the lens into Canon Customer Service (California facility) twice since purchase -- once with the lens only and the second time the lens with the 70D body I use, and both times I was told the lens was performing within spec and no service was performed. After another disappointing shoot I decided to contact Canon Customer Service again and was asked by the tech to send sample photos, so I sent some controlled test patterns shot on a tripod (see 100% crops below) that clearly showed the auto focus result was inferior to the manual focus. The techs response after evaluating the photos was that the softness the auto focus photos was within acceptable range and there was no auto focus problem. I'm confused -- how much auto focus imprecision should be acceptable in an "L" (or any) lens?

Have you used micro adjustment?

I haven't messed with the micro adjustment as I didn't even realize the 70D had that capability (I thought that was only in the pro models). Now that you mentioned it, I have done some additional research and I will definitely be giving this a try. Thanks!

My original confusion still remains about the Canon tech stating that these results are still within acceptable tolerance for auto-focus results. Does that sound right?

Mine is sharper than that, without micro adjustment.

huancayo wrote in post #17929483
My original confusion still remains about the Canon tech stating that these results are still within acceptable tolerance for auto-focus results. Does that sound right?

The images don't look even close to acceptable to me. Perhaps techs only tested the lens and not the lens/body combination.

Maybe a stupid question but do you use Single shot or AIservo focusing?
Focus results with my 60D and 24-105mm are better with single shot. My 70-200 is great with AIservo.

Definitely do MFA, or at least do some tests on objects at slightly different distances to test for front-back focusing. Suitable objects for testing are cereal boxes at staggered distances.

These test shots are using single shot mode.

(Incidentally, I get stellar sharp sports action shots using auto focus and AIServo mode with my 70-200mm f/2.8L II mounted on this same 70D body.)

I use my 24-105 with my 7D mk II in Servo all the time and get great AF results shooting sports; if you have a good copy and MFA it carefully, you should be pretty happy with it. Mine focuses as well as my 70-200, even in rather poor lighting; I didn't expect that when I bought it.

Tapeman wrote in post #17930020
Mine is sharper than that, without micro adjustment.

That can mean one of two things: Either that you are lucky and both your camera and the lens are dead on at zero, or that your camera is at -10 and the lens at +10 (of course I make these numbers up), and they compensate for each other.

Lbsimon wrote in post #17933066
That can mean one of two things: Either that you are lucky and both your camera and the lens are dead on at zero, or that your camera is at -10 and the lens at +10 (of course I make these numbers up), and they compensate for each other.

The only lens I have made a significant micro adjustment on is my 100-400L IS II.
I guess I have been lucky.

Tapeman wrote in post #17933291
The only lens I have made a significant micro adjustment on is my 100-400L IS II.
I guess I have been lucky.

My 100-400 II on my 7D2 required a small adjustment (around 3 or 4) at the long end. I don't view that as lucky or unlucky. It's just an adjustment.

As long as it doesn't hit the MA limit value, it's a slick way to compensate for tolerances in the system. The trick is to use a method you can trust and validate in actual shoots. I use my 24-105L and 70-200L on two different cameras most of the time, and I've been able to get them spot on for each. It's very rewarding to open an image in Lightroom and see the subject in perfect focus; makes the whole effort of doing a shoot totally worth it.