Focus-recompose method and "soft corners"

Started Mar 15, 2014 | Discussions thread
blue_skies Forum Pro • Posts: 11,558
Re: Focus-recompose method and "soft corners"

Ross Warner wrote:

Reading endless discussions about "soft corners" and other focus problems in lens tests, it occurs to me to ask if some of these people might be using the focus-recompose method, which many seem to use by default for everyday work. This can cause focus problems, especially in the corners.

For instance, if you're taking a wide angle picture of an off-center lighthouse, DON'T use the center point to focus on the lighthouse and then recompose! Manually move the focus point to where it should be in the scene, then focus!

There are many articles about this problem (try Google), here is a good one:


I agree with the concept that "soft corners" can be a result of focus & frame, but the author seems to want to make a general case out of it. I think that it mainly applies to shallow DOF or lenses with a significant field curvature.

The problem with focusing on your subject, being in or off center, is that you move the focal plane towards your subject. The camera will most like catch 1/3rd of DOF in front of your subject and 2/3rd of DOF behind your subject. This means that foreground will go soft when it leaves the DOF area.

If you could move this AF point forward to catch 2/3rd, or even 3/4th of DOF in front of your subject, and 1/4th behind, you will get cleaner foreground and sharper corners.

Of course, the simple way to do so is to STOP DOWN (Doesn't the bracketing app take multi-focus shots in series?)

Or, shoot multi-focus, and blend the images in post (yes, you probably will need a tripod).

Having a touch screen to move the AF point is great, if there is something in the frame to focus on in front of your subject. Focusing on your subject, even off center, will not solve the issue, imho. But then, the focus & frame method would work just as well, assuming sufficient DOF.

But again, pictures that have your subject in focus, are always preferred.

Sharp corners only matter if there is nothing else to see in the image

Get to know your lenses, framing, and subject matter - you will do fine with any method that you master.

Could foreground focus have helped here? Or would the background have gone soft? Which is better?

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