Problem with 24-70 F2.8L USM

[Mikeinminn]

I'm posting results at infinity because that is the only area in which I've found a deficiency. With every other focus test on closer subject matter (which takes in the lion share of the photos I take) the lens did very well using something pretty close to the method you posted except that I used a clock face as a "target". At shorter distances, it focuses very well both in AF and MF. I also shoot outdoors quite a bit so there were plenty of opportunities for more distant shots but I'm usually stopped down to at least F8+ which seems to mask the problem.

So I was very happy with the lens until I was shooting outdoors in lower light and sped things up (F2.8) on a more distant target. That was when the soft photos showed up. They were so soft, I was able to see it on the review screen without any magnification. I tried both auto and manual focusing using live view x10. The only way to get sharp photos from the same location was to change focal lengths enough to get away from infinity or to stop down. Otherwise it seemed close to focus but couldn't quite get there before it hit the limiter. So I tried it again the next day in better light with more time to make sure my results weren't skewed by the limitations of my camera's sensor. The result was unfortunately the same.

[Sean Setters]

Two more questions:

Explain your stabilization. What kind of tripod and ballhead/panhead are you using? What shutter speeds were you using?

[Mikeinminn]

A lightweight aluminum Manfrotto tripod (190XDB) with a 190RC2 head with a weight rating of 11 lbs. I was also using a remote to take the pics so I wasn't even touching the tripod at the time and there was no wind. Plus I waited a bit to be sure all vibration was damped. There might have been some shutter vibration because that setup is about as light as I'd want, but it was the same for all of the shots I took and the results were consistent with the pictures I posted.

The two wheel shots were both at 1/250. The F2.8 tree pic was shot at 1/6400. The F4 was 1/4000. The F8 was at 1/1250.

[Sean Setters]

Well, it sounds like you've taken care to eliminate most of the variables that can cause issues during the test. Hopefully someone else can weigh in on this. If it were me, I'm not sure I'd send back a lens for being deficient in a way I would rarely ever use it. Then again, after spending a significant amount of money, it's hard to tell yourself that.

[Jayson]

Try to return it first as suggested on the last page. If not, send it to Canon. Mine had the sort of the same problem on my 7D and my two rebels. Using at f/2.8 it worked fine outside using Servo, but anything else it was terrible. Indoors it would never focus where it was suppose to. I sent that thing to Canon 4 times in the year that I had owned it and took the very last time for them to fix the issue. Take photos in RAW and send them in with the lens on a CD to show them what is happening. That's finally what I had to do and it worked. It is now one of my favorite lenses to use! If you have the warranty, use it. Call Canon if under warranty so they will at least pay the shipping and you aren't out anything.

[Mikeinminn]

Well, I've called KEH Camera and they said that they should be able to fix it under their warranty at their facility. So in it goes. They will let me know more once they can look it over.

Sean, I thought that one over as well. But ultimately decided that, if they will fix it for free, it should come back better (I hope). I was considering Canon just because they have the best repair facilities + I thought it may just require a little tweak and not too expensive + I was unsure that KEH could do that kind of repair.

But KEH says they can, so that's where I'll start.

Good idea about the photo CD Jayson.

Thanks for the feedback.