Last night I was stalking red winged blackbirds in a marsh near my house. As is often the case, I had both a mirrorless and DSLR camera with me. For mirrorless I was shooting my Z6II, 70-20mm F2.8 with the 2x teleconverter for a total 400mm at F5.6 (2x review coming soon!). I like the light weight portability of this system. I also brought along my D6 with 180-400mm w/1.4x. This system is king of Nikon autofocus right now, and it is also fairly portable. I truly enjoy shooting both systems for different reasons which I have discussed before in this blog. As always I use back button autofocus. But should I change my habits due to autofocus changes in mirrorless?
Here is the idea behind back button focus. Since DSLRs have their focus points concentrated in a large area in the center, back button is nice because you can focus on your subject, then put it outside the focus points for a creative composition, and not worry about the shutter engaging autofocus every time you take a picture. This is often called ‘focus, recompose and shoot’. If your autofocus point isn’t on your subject, you don’t want autofocus focusing on a new subject every time you hit the shutter. Using back button focus takes focusing away from the shutter button so you don’t have to worry about this.
But mirrorless adds an interesting angle to this topic. Since there are focus points across the entire viewfinder, I never need to focus, recompose and shoot. I just toggle my focus point to my subject and take the picture. Now I could just use my shutter button to do both things (focus and shoot) and use my thumb to toggle the focus point. In essence we are still using two fingers in the process, but now my thumb is toggling the focus point instead of pressing the AF-C button (I always use AF-C because my subjects frequently move).
But at this point I still think back button focus is the way to go for me. Why? Here is what happened last night photographing blackbirds. I was walking through tall reeds, and there was a lot of plants between me and my subject. I carefully lined up so I could shoot through the reeds, but I had one issue. March is notoriously a windy month on the front range of Colorado, and last night was no different. The tall reeds were blowing in the wind, and about 50 percent of the time they would come between me and my blackbird. If I had been using shutter button autofocus, about 50 percent of my images would have been focused on foreground reeds, not the backbird. As it was I was using back button autofocus. I focused during a clear moment on my bird, and stopped pressing the AF-C button. Then I just blazed away taking pictures using my shutter button…with no focus engaged.
Now this is a specific case, and I do see merit in the idea of changing how we focus using mirrorless. And as predictive AI focus modes get better, it might make even more sense to switch back to shutter button autofocus. I’ll revisit this idea when the Z9 comes out. New technology, new ways of doing things….stay tuned.