8.30.2015

Why I like my Sony a6000 more than my Olympus E-M1: Part 5: Autofocus with native lenses

When it comes to autofocus with native lenses (Sony E mount and Olympus mFT mount), until two months ago, I would have given the Olympus the edge... slightly. I feel certain that when using single autofocus (AF-S), the Olympus is a tad faster than the Sony. This seems to be especially true in low light situations. Yet, I've never noticed the difference to be enough to actually make a difference in my type of shooting.

However, in the last couple of months, I've begun to use what is called "back button focus" (BBF).  I will explain how this works further below, but it basically allows you to obtain either single autofocus without changing out of the continuous autofocus mode.  

It is with continuous autofocus that the a6000 shines (compared with the E-M1). On the a6000 I find AF-C to be as fast and confident as AF-S.  On the Olympus I do not have the same confidence in AF-C.  It seems much slower and more tentative, going in and out of focus repeatedly and at a rapid pace, as it seemingly hunts to achieve  focus.

Now let's go back to setting up "back button focus" on the a6000:

I have set the a6000 to operate in AF-C. Then I  programmed the AEL/AFL button on the back of the camera to be a focus lock button. In the menu, you also need to turn off "AF w/shutter". I generally I use the smallest single "flexible" focal point.  (There are other good focus area options that are beyond the scope of this post.)


I've programmed this button as the AFL button.
It's in a perfect location for my thumb while maintaining a good grip.
The button is a nice size and gives a nice click.



This is how BBF works:

If you are photographing a still object like a landscape, press the AFL button with your thumb and release. I generally use the center focus square to achieve focus on the intended main subject, and then recompose if the main subject is to be off-center. You can now take one or more images without refocusing.

Now let's say a deer runs across your view.  Here's a chance to use continuous autofocus. Just press and hold the AFL button and it will continuously focus as you pan the camera, but you must keep the focus point on the deer. There are some other cool focusing options that I have played with but not used.  In particular, the AF-C with "lock on" seems to have great potential, as it would in this case lock onto the deer and follow it around the frame. Additional features can be realized by choosing a different focus area, like wide or zone, but I won't go into that here.

Now with the Olympus, you can also set things up with BBF. It's just that AF-C seems so sluggish.  But more importantly to me, the actual button is in the wrong place and too small and squishy. I guess it's an ergonomics issue for me.

This button is too far to the left to easily reach with your thumb while maintaining
a good grip. It's also smaller and softer than I like.



2 comments:

Leonardo Prasetyo said...

Hi Peter,

Thank you for this great article. I have the same setup but I'm its not working for me. Particularly, it fails when I recompose.

I also set the focus mode to AF-C, so I'm able to capture moving subject while pressing the AEL button. That works.

The problem only happen for still subject, where I set the focus using AEL (then release the btn) and recompose to rule of third. And the subject becomes out of focus and I shoot it.

Peter F. said...

Hi Leonardo, Hmmm. See paragraph 5 again. In the menu did you turn off "AF W/Shutter"? If you don't turn that off the camera will refocus when you half press the shutter. So if you use the focus lock and release, then recompose, you will re-focus when you half press the shutter. This wouldn't be an issue whey you are holding the focus lock in and following a moving subject.