This is a telephoto Canon EOS prime lens that Sigma discontinued about a decade ago and they languish on eBay for under $250 USD because they often don’t allow proper aperture control when mounted on current Canon bodies. In older bodies, the camera would issue a sync command twice before requesting lens info and since Sigma reverse engineered the EOS communications protocols, these older lenses would wait for the 2nd sync command before responding. Newer Canon bodies now only issue a single sync command so an Error 01 will result if you try to change the aperture from its maximum opening.
The lens is otherwise a very good performer, with 10 elements in 7 groups, 2 super low dispersion elements with true internal focus and a nonrotating front element. There is an integral sliding hood. In terms of size and weight it is a dead ringer for the Zuiko 300 mm f/4 PRO. When used with a m43 smart adaptor, there appears to be no issue with aperture control. I plan to use it with my Metabones Speed Booster to give a 290mm focal length at f/4, again very similar to the Zuiko 300mm f/4 PRO.
I’m currently using the Zuiko 75-300mm zoom which has acceptable image quality, but I’m always looking for the best prime lens performance. Here’s what the Zuiko 75-300 MTF curves look like at 300mm @ f/6.7
And here is what the Sigma 400mm f/5.6 looks like. Top row is Sigma 400 using Kipon smart adaptor at f/5.6 and f/7.1. Middle row is with Metabones Speed Booster S at f/4 and f/7.1. And bottom row is with Metabones Speed Booster T Ultra at f/4 and f/7.1.The Sigma 400 with the Metabones Speed Booster outperforms the Zuiko 75-300mm at equivalent apertures as expected (f/7.1 vs f/6.7). However there was no AF with the Speed Booster T Ultra, only with the older Speed Booster S. It seems to happen only with this Sigma lens for some reason. It may be that I need to update the firmware on the T Ultra.
I took some test shots at the fine print on boxes some twenty feet away on my kitchen counter and it shows how much better image quality is with the Sigma prime. Taken with the E-M1.2 at ISO 1600 from left to right, f/4, f/5, f/6.3, f/8.and now taken with the Zuiko 75-300 at 300mm, f/7.1 and f/8.You can view these shots together at 100% size here: https://dl.dropboxusercontent.com/u/4852049/allcompared.jpg
Clearly the Sigma 400 with Speed Booster S wide open at f/4 is already better than the Zuiko 75-300 at f/7.1, while the Sigma 400 closed down to f/8 is incredibly sharp. AF speed on the adapted Sigma appears to be quite fast and reliably very accurate. If it wasn’t raining all weekend, I’d be outside catching some birds shots to verify the Sigma 400mm’s performance.
I caught this black grey squirrel in my yard this afternoon about 50 feet away and up a tree to challenge the focusing system. Left is the 75-300mm f/7.1 and right is Sigma 400 @ 300mm f/7.1. You can view the 100% crop here: https://dl.dropboxusercontent.com/u/4852049/squirrelcompared.jpg
In case you’re wondering what that hazy horizontal smear is below the squirrel, it’s the fishing line I strung from between the back of my house and the large silver maple. I had my son’s unicycle toy riding back and forth on it for my C-AF tracking tests in an earlier post.
Some more comparison shots. You tell me which one is which!And here are the links for 100% sized versions: https://dl.dropboxusercontent.com/u/4852049/femalemallardcompared.jpg