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November 24, 2021

Fixing a Stuck Zoom Mechanism on a Canon EF-S 15-85mm f/3.5-5.6 IS USM Lens

Filed under: Uncategorized — admin @ 4:22 pm

The Canon 15-85mm is one of my favourite EF-S mount lenses to use on a Canon cropped sensor body such as a 90D. It’s sharp, with nice bokeh, is lightweight, and covers a great walkabout range (24-136mm) with great optical characteristics. Although not being touted as a pro grade lens, it actually employs Canon’s famous ED glass and performs well as you can see in many of the galleries at of the past few years. However, my 15-85 began showing mechanical problems a few months ago; it eventually would not zoom wider than 35mm due to what felt like a mechanical blockage.

Fortunately, despite what I’d seen in some youtube videos about this lens, fixing the problem in my case did not require full disassembly of the lens.

Canon 15-85mm lens fully assembled

The first step necessary in this repair was gently pull back the rubber zoom ring. I could do this fairly easily just using my rock climber fingers, but some readers might find this easier to start with a plastic “spudger” tool such as gets used for phone disassembly. After that, I pulled back one end of a transparent cover that had tape-like adhesive on its ends. That revealed enough of the zoom mechanism to expose the problem: a loose set screw in a rotating groove. See the red arrow in the photo below.

One loose screw. The author might have a few more…

Tightening that screw with a small Philips screwdriver removed the problem. I did not try to put in any threadlock or other glue so as not to risk that getting into the optics, but I did apply quite a bit of torque on the screwdriver to tighten it. Hopefully that will hold it for a while. Reassembly was easy; the transparent cover adhesive was reusable and the rubber zoom grip could be eased back into place without much effort. A fairly quick and easy repair.

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