Canon EF 400mm f/2.8L IS Repair Topic

[bdunbar79]

I sent a lens into Canon to check the AF assembly and lens calibration upon purchasing a used lens.

I got the following return disposition:

"Your product has been examined and upon close inspection the exact cause could not be identified but it was found that causing front focus from time to time. Electrical adjustments were carried out on the AF assembly. Product function were confirmed. Adjustments with EOS 1Dx."

Does anyone know exactly what this means? I've just never seen that before. Thanks.

(Getting a straight answer from someone at Canon is not easy either.)

 

[AcaciaRee]

Sorry to hijack this post, but I've just signed up and am unable to start a new topic until I've posted at least 2 replies! This topic was the closest I could find.
We're in New Zealand, and my husband recently purchased a second hand 400mm f2.8 (non IS) lens. It's an older lens (made in 1994 canon tells me from the build code), but seems in good order......except that the focus seems slightly off. On large subjects it's fine, but smaller subjects, such as a bird the focus is often just to the right, or just above. My husband is using it on a tripod. Canon suggested it might need calibrating? Is it the second that gets calibrated? Or does the camera need calibrating to work with this lens?

Also wondering if anyone has one of these lenses and could help with the function of some of the buttons on the side? It didn't come with a manual, so we're a bit unsure what some of them do. I've attached a photo. In particular were wondering about the bottom two?

Thanks for any suggestions.

 

[Random Orbits]

I've had something similar with one of my lenses, 24L II. I bought it used, and it focused horribly from f/1.4 to even past f/5.6. It went in with the receipt from the seller (still under warranty), and Canon found that the lens AF settings had to be adjusted. My camera never went in, so they calibrated the lens against their reference metrics. They didn't replace any parts either, so it must be reprogramming/adjusting the lens back into spec. It has worked flawlessly ever since.

AcaciaRee, I'd suggest sending your lens in for calibration. It might also be worth checking the focusing performance with another long lens if you have it or can borrow one. Perhaps the camera's AF module has been knocked around so that the AF point in the viewfinder is not matched with what it is actually focused on. With shorter focal lengths, the problem might have been hidden. However, if the camera does work properly with other long lenses, then it's most likely a lens issue.