Canon firmware fixes 40mm focus failure


posted Monday, August 27, 2012 at 2:02 PM EDT

Canon's EF 40mm f/2.8 STM lens. Click for's Canon EF 40mm f/2.8 STM review!A few weeks ago, we told readers about an issue with Canon's EF 40mm f/2.8 STM lens, which only recently began shipping. According to the company, pressing on the lens barrel while the lens was mounted to a camera could cause autofocus to stop working.

As a temporary workaround, the issue could be resolved simply by reseating either the lens, or the attached camera body's battery. Canon 40mm shooters can now stop fumbling with their battery door or lens, though, as the company has issued its promised firmware update to resolve the issue.

The new firmware is applicable to lenses whose third serial number digit is a 0, 1, or 2, and you'll need access to a Canon EOS-1D X, 5D Mark III, or Rebel T4i camera body from which to apply the update.

There's are two very important provisos, however. If you're applying the firmware from a 5D Mk III, it is vital that you first update the camera itself to firmware version 1.1.3. Failure to do so before applying the lens firmware, says Canon, can result in the lens itself ceasing to work! You'll also need to attach the lens directly to the camera body before updating; using an extender or extender tube may prevent a successful update.

If you don't own one of the above three camera bodies, you won't be able to update the 40mm lens firmware by yourself. If that's the case, Canon recommends contacting a service center for assistance.

More details and the firmware update can be found on the Canon website.

New firmware fixes focus issues for Canon's EF 40mm f/2.8 STM lens.
Photo provided by Canon.