Lens out of focus

TheoPalvi

Hi, I was wondering if anyone had the same problem.
I've been using my canon 60D for 8 months, and in the 8 months I've used different lenses on the body (fix 50mm, efs 18-135mm macro and an EF 75-300mm). All the lenses were focusing perfectly. Lately my 18-135mm lens still focuses perfectly but my 75-300mm lens is back focused.
I tested the lens by putting 3 AA batteries in line about 150mm apart. I put it in line with the lens so that the batteries are all different distances from the camera. Camera was on manual setting, af single point, af on, on a tripod, clip on flash and 2 sec delay to avoid any camera shake.
I let the camera focus on the middle battery and the rear battery is in focus.
I let the camera focus on the front battery and the middle battery is in focus.

If I take off the lens and put it on my D1100 Canon, with all the same settings in manual mode, it's perfect.
How can a lens that worked perfectly all the time on a certain body suddenly have a focus problem? How can I fix this?

Thanks in advance.

Nicole1982

I have the same problem and but I have a 18-200mm Tamron and a Canon 100mm macro is usm. Both don't focus well on the 60D. I even use a tripod and no difference. I don't know how to calibrate it, but would like to learn how.

bruto

I don't know much about this combination, nor about how that Canon adjusts for focus, but it's actually not all that rare for a zoom lens to have different optimal focus at different points, as well as on different cameras.

If you do have the option for fine tuning focus on this setup, I suggest you try it at various focal lengths and see if it varies, and then you may have to decide what compromise to make.

I frequent a more Nikon-centric world, but it's not uncommon for even very good cameras and lenses to vary, and often to be off at certain focal lengths more than others. It seems to be a lottery, sometimes.