I haven't been on the board for a while, so I might have missed something, but it doesn't look like this topic has been discussed much recently. I discovered that quite a few Canon lenses, including a number of recent RF lenses, have firmware updates available. EOS Magazine has compiled a list, and I thought I would share in case this is new information for anyone. (Apologies if this is old news.)
Your lenses might already be current, but if you have a lens on this list, it might be worth a look. You can check the lens firmware versions in-camera.
Very interesting article which highlighted for example that there were firmware updates for the 500 II and 600 II f/4 lenses which can only be performed by Canon. Thanks for sharing.
I sent my 400 2.8 II in for firmware update just a few months ago. I was very surprised, it made a noticeable difference. Since the update I get more images in each burst that are keepers, less variance from image to image. Updating firmware on this lens definitely helps focus accuracy. Wish I had known about the update a couple years ago.
