Sports shooters considering Sony's speedy a9 have one major hurdle to overcome: glass. There's a dearth of long, fast primes available to Sony FE shooters, and it seems like using off-brand glass while you wait for Sony to catch up just isn't a great option.

In this video, photographer Dan Watson of Learning Cameras tried both the Sigma MC-11 and Metabones Mark IV lens adapters to test how well the a9 worked when attached to the Canon EF 300mm F2.8L IS USM and Canon EF 400mm F2.8L IS USM (both version 1**)

Watson mainly wanted to test the focusing capabilities, and unfortunately, the results were somewhat disappointing.

Before you dive into the video, it's worth pointing a few things out. Our own Rishi Sanyal has tested the focus capability of the a9 with adapted lens, and points out a couple of caveats to Watson's otherwise solid points:

First, the performance of far off-center AF points depends on the lens. While Watson is correct in pointing out that they don't perform well with long lenses (despite working astonishingly fast with Sony's own 100-400 F4.5-5.6), they do work well with shorter focal lengths (we've had success with a Sigma 85/1.4, Canon 35/1.4, 24-70/2.8, etc.). With these wider lenses, 'Wide' area mode will continue tracking subjects to the extremes of the frame.

Second, Sony A-mount lenses adapted with the LA-EA3 adapter do shoot at an impressive 10 fps with autofocus, something we confirmed with the 50/1.4 (as long as you've updated the firmware of the adapter).* With the Metabones and Sigma adapters though, as with all Sony FE bodies, only the L drive mode offers continuous focus. And it's actually only 2.5 fps, not the 5 fps Watson mentions (technically L is 3 fps, but it slows to 2-3 fps with continuous focus).

With that out of the way, Watson's video is a great resource for seeing how well (or not) the a9 performs when attached to the long, fast Canon primes sports shooters love. And while single-shot focus with central points is speedy and almost 100% accurate with long adapted lenses, the lack of true subject tracking (Lock-on AF modes) or continuous focus at speeds higher than ~2.5 fps (or in video) will probably be a deal breaker for many fast-action photographers.

Once you've lost the impressive high speed shooting advantages Sony baked into the a9, you might as well be shooting with any other camera. Moral of the story: stick to Sony glass and hope they keep churning out new lenses at break-neck pace.

You can watch the full demo for yourself up top. And if you're considering jumping ship from Canon to Sony, keep this information in mind – like all previous Sony bodies, you'll only have access to the a9's slowest continuous drive mode when you're adapting your own glass.


* We've not yet confirmed the performance of off-center points with long A-mount glass.

** Correction: The first version of this article claimed the lenses used were the 300mm F2.8L II and 400mm F2.8L II. They are, in fact, Version 1 of both these lenses. The text has been corrected to reflect this.