Canon 20D Err 99 Resolved by New Battery

I’ve been using my reliable Canon 20D for a while (11 years?), frequently employing a Tokina AF 100mm F2.8 macro lens for detail work. This is one of my favorite lenses and is great for bringing out detail I wouldn’t be able to see with the naked eye, but around six months ago I began occasionally receiving the generic “Err 99” when trying to use the lens. My other lenses (a Canon EF 24-70mm f/2.8L and EF 50mm f/1.8 II both worked fine, so I figured the problem was with the lens.

Turns out it had a surprising (and cheap) solution: the batteries.

When the problem originally manifested itself as a simple error that’d only occasionally happen, I would then turn the camera off and on and try again, and usually the lens would work. It also appeared correlated with the aperture used, so I figured the lens was failing; perhaps the iris was binding at some point. Last week I found that the error was occurring more frequently, and would be coupled with a low battery indicator that only appeared after turning the camera back on.

Since I was using the original two batteries I ordered two new ones via Amazon (STK’s Canon BP-511 2200mAh Battery, 2 Pack for $24.99) and they arrived today. Once charged up I tried them with the Tokina lens and it’s now working great. I’m still able to reliably reproduce the issue with the older batteries, so a solution has been found.

Apparently the Canon lenses use a bit less power, or perhaps are more tolerant of lower voltages. Either way, I’m glad everything is working well. I might even think about getting a new camera body… Although I’ll probably wait until this one dies. I must have balanced use pretty evenly across the batteries too, because they both show the issue to the same degree… What’d normally be good just confused things.

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