Lens Auto Focusing issues

Jeff_Milo

Need some help please. I lent a friend who just bought a Canon 50D my old 17-85mm 4-5.6 IS USM to shoot with for the day as she didn't have anything but a 50mm 1.8. I have not used this lens in probably 2 years, but the last time I used it I remember it working fine. When she tried to use it yesterday it would not autofocus between basically 50mm and 85mm. She brought it back to me last night and I tried it on my cameras and had the same issue. Has anyone else had this problem? is it a motor problem? I tried cleaning the nodes with an eraser but no better. Is it even worth having it looked at by Canon?

Thanks for your help.

ziggy53

Jeff, what do you see if you shine a small LED flashlight through the lens by itself, from the front and from the back?

As you zoom?

Jeff_Milo

Looks like maybe some dust specs on the inside of the lens but not sure. Am I looking for something specific?

ziggy53

Jeff_Milo wrote:

Looks like maybe some dust specs on the inside of the lens but not sure. Am I looking for something specific?

Compare the view against a lens which does not have the AF problems. Is there any internal diffusion? (Fungus or mildew, for instance.)

Jeff_Milo

ziggy53 wrote:

Compare the view against a lens which does not have the AF problems. Is there any internal diffusion? (Fungus or mildew, for instance.)

Not that I can see just looks like some dust specs

ziggy53

Unfortunately that's the only thing I could think of that "might" have caused an AF problem specific to a zoom range. It does sound like you would have to send it in.

If you like the lens I suspect it would be more economical to repair than replace, but you should indicate a maximum/limit if you submit the lens for repair.

Jeff_Milo

Thanks for your help. Much appreciated!