Canon released a firmware update (download here) for the EF 40mm f/2.8 STM ($199, click here) lens. The lens had a problem with AF if
pressure is applied to the lens barrel while the lens is mounted to the camera (pressure can be applied even while attaching the lens cap while carrying the camera with the lens attached in a bag), the autofocusing function of the lens may stop working.
Firmware rel. 1.2.0 addresses the problem. Your lens is affected only if
the third digit in the serial number is either 0, 1, or 2 (xx0xxxxxxx, xx1xxxxxxx, or xx2xxxxxxx).
To upload the firmware you need a compatible DSLR. These are the EOS-1D X, the EOS 5D Mark III and the Rebel T4i/650D.
Thank you for using Canon products.
Canon has released a firmware update for the EF40mm f/2.8 STM Interchangeable Lens for Canon Digital SLR Camera.
EF40mm f/2.8 STM
Firmware Version 1.2.0 addresses the following phenomenon.
1. If pressure is applied to the lens barrel while the lens is mounted to the camera (pressure can be applied even while attaching
the lens cap while carrying the camera with the lens attached in a bag), the autofocusing function of the lens may stop working.
Firmware Version 1.2.0 is for lenses with Firmware Version 1.1.0. If the lens’ firmware is already Version 1.2.0, it is not necessary to update the firmware.
The lenses with the following serial numbers are equipped with Firmware Version 1.1.0:
The third digit in the serial number is either 0, 1, or 2 (xx0xxxxxxx, xx1xxxxxxx, or xx2xxxxxxx).
Lenses with serial numbers other than those listed above are equipped with Firmware Version 1.2.0.
● If an extender, or extender tube, is attached to the lens, the firmware may not be successfully updated, so make sure that you detach
the extender or extender tube before the firmware is updated.
● A supported camera* is required for the firmware update.
Cameras that can be used for the firmware update:
Canon EOS-1D X, Canon EOS 5D Mark III (*), or Canon EOS REBEL T4i
*When using a Canon EOS 5D Mark III for the firmware update, please make sure to update the camera’s firmware to Version 1.1.3 or
later. If a Canon EOS 5D Mark III equipped with Firmware Version 1.1.2 or earlier is used, the lens may stop working.
Customers who do not own any of the cameras listed above, but wish to have the firmware of their lenses updated, are asked to contact our service centers.
The new Firmware Version 1.2.0 can be downloaded by clicking here.
This information is for residents of the United States and Puerto Rico only. If you do not reside in the USA or Puerto Rico, please contact the Canon Customer Support Center in your region.
Please register your EF 40mm f/2.8 STM. By registering, we will be able to notify you via email when future service updates are available.
Customer Support Operations
Canon U.S.A., Inc.