I used a Canon T5i from 2014 until the end of 2020.  I took tens of thousands of shots on that entry level DSLR.  But it was starting to show its age, and would occasionally stop working altogether.  So, I bought into the Sony E mount with a Sony a7RIII.  Until I purchase the Sony FE 200-600 mm f/5.6-6.3 G, I am adapting my venerable Canon 400 mm f/5.6 L for bird photography.  This legendary lens opened so many wildlife photography opportunities to me.  Here, I will share my experience adapting the Canon 400 mm f/5.6 L onto a Sony mirrorless body with a Sigma MC-11 adapter.

Autofocus performance:

Autofocus is probably the most concerning part of adapting lenses from one system to another.  I’ll give recommendations and warnings, but your results may vary with another adapter such as the Metabones.  I’ve also tested Fotodiox autofocus extension tubes for Canon EF attached the the Sigma MC-11; the system seems to perform the same with or without them.

With all settings, I tend to have better results with AF-C than AF-S, even for still subjects.  Also, all autofocus modes and area modes work best if you manually focus about 80% of the way there, then autofocus to close the gap.  I rarely have issues if I start by getting it “close enough” by manually focusing, which isn’t difficult with the viewfinder on the a7RIII.  You can even turn on focus peaking if you want an extra assist when manually focusing.  Once you’ve locked on with autofocus, the a7RIII rarely loses a bird.  The lens will hunt and get really lost if you try to focus between too large of distances.  However, it feels like it can acquire more dramatic focus pulls in brighter light.

Autofocus seems to be the strongest in the center 20% of the frame.  It feels a little stronger in crop mode as well.  This could be a software or lens based problem, but I have a theory that it’s the narrow diameter of the Sony E mount working with longer flange distances on adapted lenses.

In all autofocus areas, rapidly tapping the AF button yields more accurate results.  These micro-adjustments prevent the autofocus system from getting lost.  If the autofocus system cannot decide on a subject begins to rack focus from the foreground to the background, it will pretty much never decide on a subject.  Again, this adapted lens really won’t excel at excel at focusing from infinity to close distances without a little bit of manual focus help.

Finally, this system will occasionally refuse to autofocus at all until you manually focus it about 95% of the way to the subject.  Simply turning the camera off and back on seems to clear up any autofocus bugs.

Image quality:

The Canon 400 mm f/5.6 L is quite an old lens, but still produces razor sharp images.  Since switching to full frame, I’ve started enjoying images that portray more of the environment and show the bird smaller in the frame.  This sensor captures an incredible amount of detail for these scenes, so the bird still comes out very deailed.  In the past, I cropped pretty heavily for small birds and would  my a7RIII into crop mode for an 18 megapixel image.  I discovered that this camera and lens combination produced detailed full frame results which could be cropped in post to the reach of an apsc camera.

Stabilization:

The Canon 400 mm f/5.6 L does not have image stabilization, but the Sony a7RIII does.  Shooting at 400 mm and f/5.6 in low light is tough, but Sony’s sensor stabilization help a little bit.  I find that as long as the subject is still, I can reliably get about two stops of stabilization from the Sony a7RIII.  In a burst, I can produce sharp shots at 1/320s or even 1/250s.  Coming from an old crop sensory DSLR, this is revolutionary.  When I use the Sony 200-600 mm f/5.6-6.3 G with its lens stabilization, I can shoot at 600 mm down to shutter speeds of 1/100s or slower.  I suspect results will be similar with other native Sony lenses for E mount.

Focus areas:

For most birds on most backgrounds, I start by using “Expand Flexible Spot.”  Autofocus is prioritized to a small zone, but has a larger sized box around it.  If a bird moves out of the small zone, the surrounding points will usually lock on to it.  If I’m close to a bird and trying to be very precise, I’ll switch to “Flexible Spot: Small.”  In this mode, autofocus is limited to the points within the small zone.  This is great when you can position the small zone right over the eye of a bird.

I included a few sample photos that I’ve shot with this camera/lens combination.  Feel free to reach out to me if you have any questions about using the Canon 400 mm f/5.6 L on a Sony a7RIII!

– Kameron