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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 https://davebaar.com 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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