Autofocus question

[rgs]

I have come to the conclusion that, on my 50D, the best autofocus solution is to use just the center focus point and recompose. It seems much faster and more precise than relying on the camera to decide where to focus and constantly shifting the focus point is much slower than recomposing.

I just wonder if others have come to the similar conclusions or am I missing something. What techniques do others use? Some cameras have so many focus points and such sophisticated systems it seems a shame to use such a low tech approach.

Thanks for reading. I am eager for you comments.

[Rhossydd]

it seems a shame to use such a low tech approach.

Not really, it's whatever works for you.

I end up using a similar approach myself for most things, but much will depend on what you're shooting, what camera you have and how it's set up.

[telyt]

I have come to the conclusion that, on my 50D, the best autofocus solution is to use just the center focus point and recompose.

Canon advises against this technique when DOF is shallow, and I agree.

[rgs]

Because recomposing might change the focal plane? Where did you find Canon's recommendations?

[Slobodan Blagojevic]

Because recomposing might change the focal plane? Where did you find Canon's recommendations?

Yes, it changes the focal plane and matters in situations with shallow DOF. Canon's recommendations in this article:

http://www.learn.usa.canon.com/app/pdfs/quickguides/CDLC_Accurate_EOS_AF_QuickGuide.pdf

[BarbaraArmstrong]

Moving focus with a touchscreen is easy, and I often do that when a camera has that capability (my GH2 for example).  Otherwise, I do just what you are doing, focusing with a central focus point on my subject and recomposing as needed.  Face recognition and multiple focus points are more information than I want.  --Barbara

[rgs]

These are all very helpful. Thanks very much. I have saved the Canon document. It's much more thorough than the camera manual. I also found some videos on the Canon site that go into AF with the 60D and 7D that were helpful. I started this thread because I was sure there was more to AF than I had thought of. Thanks to all.

[Ken Bennett]

The center-point-and-recompose technique was standard for many manual focus cameras, and of course the early AF cameras had but one single focus point in the center of the frame. These days, even with many focus points, often the most accurate one is in the center. So you are walking a well-trod path with your technique.

It will work fine with the major exceptions of using wide ange lenses at close distances, or very fast lenses wide open at close distances. Then the recomposing will alter the subject distance enough to throw it out of focus.

With my 40D and 5D Mark II I find that using the outer AF points works somewhat better in Single Shot AF, and not so well in Continuous.

[Fips]

Canon advises against this technique when DOF is shallow, and I agree.

I agree, too. The two problem are: i) you moving with respect to the subject and ii) field curvature of the lens.

[Jeremy Roussak]

Canon advises against this technique when DOF is shallow, and I agree.

Jonathan Wienke, who used to frequent this site, had an article on why it shouldn't be used: http://www.outbackphoto.com/workshop/phototechnique/essay06/essay.html.

Jeremy

[BarbaraArmstrong]

Very interesting piece!  Short enough to absorb easily, and interesting enough -- powerful in concept -- to cause one to reconsider technique.  It has certainly caused me to reconsider.  --Barbara

[Petrus]

Canon EOS-5DII used to be my work camera, and often the center AF spot was the only one that worked reliably. Shooting full open did mean that I had to lean back a bit after reframing to take the focal plane shift in account. It works, basic descriptive geometry in action... With better cameras, or at least better AF systems (Nikon D4 now) it is possible to use more AF points even in low light situations. If not using largest apertures at close range it is even possible to let the camera use a cluster of AF spots for "semi-auto" focus. With D4 I have sometimes started to use continuous autofocus with 9 or 21 focus spots, as it is easy to move the cluster with the joystick. Not for extreme shallow DOF but "normal" shooting. "Full auto" I do not like. Cameras are getting better, but matte screen without any focusing aides with MF was actually most representative of the final picture, kind of miss that Canon F1 over 30 years ago...

[stamper]

It isn't recommended to use the recompose method when shooting in evaluative metering unless you lock the exposure.