Canon 7D: Problem Focusing With Spot AF

category: Cameras • 1 min read

I use the Single Point Focus for around 60% of the photos. I use the Zone Focus for around 30% of the photos. The rest of my photos are made with the other modes: expansion or spot. I don’t think that I’ve ever used the 19 points AF.

The other day, I was taking photos of a very “deep” beach. I wanted to get the focus right, time to switch to Spot-AF. I won’t get it anymore precise. But Nooo, it doesn’t focus, it hunts. I can’t get the “darn” AF to work properly. What’s wrong? I recently did the micro-adjustment, what gives?

  • First, I ranted and raved.
  • Second, I fired a couple of brain cells at the same time and found the source of my problem.

  1. The spot AF only works on the center focus point.
  2. The Auto Focus system works with contrast. No auto focus in the world can focus on fog, on a clear blue sky or on a smooth white wall.
  3. It’s much more difficult to find a contrasty spot for the spot af to focus on.

The point, I was focusing on, was flat and grey. No contrast! I moved to a more contrasty spot and the auto focus worked properly. The problem is that it wasn’t where I wanted. I had to switch back to the single point AF.

The autofocus needs contrast to work.