Interesting Video on Auto-Focus

category: Cameras • 2 min read

Oldies but goldies. BH Photo Video regularly hosts presentations from Canon and other manufacturers. They are the greatest (in volume) independent camera store, no chain, no franchise. I’ve discovered through dpreview, some old presentation from 2009 about the Canon autofocus. It’s old, 2009, and it doesn’t cover any current camera. You know what? It’s not about the cameras, it’s about how does the auto-focus behaves. Your brand or camera model is irrelevant. It’s a Canon presentation that discusses Canon, but from talking to some Nikon friends, it also applies to Nikon cameras.

The details are Canon, the principles apply to any dSLR, any brand including Nikon, Sony, Pentax and Olympus. The video deals with the principles and that hasn’t changed. Since then, there has been many technical improvements, but all auto-focus systems use the same design philosophy. These videos have solved a few mysteries, like:

Q: Why is the first photo of a whole bunch fuzzy?

Sometimes, the first photo is fuzzy, it’s like the IS didn’t have time to kick in. I wait for the ½ second for the IS to kick in, but nonetheless, it’s blurry. Why?

This was explained in the video: The auto-focus is set to AI Servo to track the subject, but the subject is not moving. The AF moves the focus until it figures out that the subject is not moving, and then it’s in focus. The solution is switch to the one-shot AF.

Q: How to get all the photos in focus while tracking at high speed?

  1. Use the AF-On button
  2. Use the IS on the lens
  3. Select a focus point with good contrast
  4. Focus for a full second before taking the shot to give time for the AI Servo to analyze and do its work
  5. Finally hammer down the shutter

And many others like that. By the way, it’s the same on Nikon, according to Kathy who uses 2 Nikon D3.

It’s 3 videos, totalling just under 2 hours. That’s long, but worth it.

Video 1: How does the auto-focus behave so you can control it

Video 2: How does the auto-focus behave so you can control it

Video 3: How does the auto-focus behave so you can control it