40-150 2.8 PRO slow focus mystery may have been solved

abe4652 wrote:

Colin K. Work wrote:

abe4652 wrote:

I've has issues with slow focus with my EM1 and this lens.

Today, by chance, I played with the focus point setting. I realized that the AF point was set to small AF. I changed it to regular.

My speed increased a lot. I don't know if it solved the issue completely, but I did notice much more responsiveness.

You have to think how the AF works - it needs contrasts to make focus decisions. With a small AF point on a telephoto, it's very easy to end up with the camera trying to lock on to an area with no or little contrast.

Depending on your subject, you may find that the wider 9 point grid works even better. I tend to switch between this and normal single point and find focus to be very fast, with or without the TC.

The 9 point grid might easily lock on something other than the intended center.

Of course, which is why I said "depending on your subject" - there is no correct answer to this other than understanding how the AF system works and using the best mode for the subject. I guess that's why you get a choice :).

If I'm shooting yachts, it is quite likely that the small AF point will end up over a sail or hull with no detail or contrast and won't focus at all. At the framing I often use, standard AF point is perfect for focusing on a crew member. When capturing the whole boat against sea & sky, 9 point means very positive lock and little chance of being distracted.