Sigma confirms: no support for Canon mirrorless

I purchased a Canon M5 and a Canon M3 for Christmas, and have been trying them out.

The M3 was a gift for my daughter, as a travel-friendly alternative to her 6D. She also got the 22mm f/2 M-series lens and a generic (Meike) mount adapter. My wife received the M5 body as an upgrade to the EOS 400D (inherited from our daughter some years ago). The M5 was the body-only "starter pack" that comes with the Canon EF/EF-S to EF-M mount adapter (without the tripod extension, frustratingly).

This offered a good range of options to test the lenses we had on hand. We quickly found a problem with the Sigma 18-250mm f/3.5-6.3 DC MACRO OS HSM. This is a handy 'travel' lens and thus seemed ideally suited to the mirrorless body, even with the added bulk of the adapter.

In brief, the Sigma 18-250mm works on both bodies, but there are problems when powering off. Neither body switches off fully for one minute. It seems that the lens is holding onto the sensor for a full 60 seconds after the switch is turned off. There is a distinct click after 60 seconds - perhaps releasing the sensor (just guessing). The M3 screen goes blank but is not off. Opening the battery cover will turn it off completely. The M5 seems to power down but cannot be turned on again immediately. Removing the battery will re-set things.

I tried this with various combinations of lenses, adapters, SD cards and batteries (I also purchased a couple of generic cells that work well, though neither the M3 nor the M5 will display the remaining charge, as expected). I also tested an older Sigma 17-70 f/2.8-4.5, which does not seem to have any issues.

I wrote to Sigma in Switzerland, where I am based, and they contacted Sigma Japan. Their response: "A Happy New Year. As you may know our lenses are optimized to DSLR cameras. So there may be incompatibility issue when it attached to Canon M series cameras. In other words, our products to not support Canon mirror less cameras." (my emphasis). Canon's Swiss rep. added, "We are sorry we could not give you any better news."

Perhaps I was naive to expect anything different. However it does seem short-sighted from Sigma. They promote the 18-250mm as a travel-friendly compact zoom, and I would not be alone in expecting it to be a useful pairing with the smaller mirrorless bodies. Buyers be warned.

This is my wife's favourite lens, as she likes to shoot birds as well as bugs and flowers. It is disappointing that it is no longer reliable. The M5 is a nice upgrade to the 400D of course, and it is too late to return my purchase to Canon (which is not at fault).

In the hunt for the ideal super zoom, I will take a closer look at the Canon EF-M 55-200mm f/4.5-6.3 IS STM, though it lacks the range and macro facility of the Sigma. I had considered the Tamron 18-270mm F/3,5-6,3 Di II VC PZD, when buying the Sigma three years ago. I would welcome suggestions on good alternatives!