Use Spot Focusing - Better Photos... Now!

Having all of the technical knowledge and technique in the world doesn't mean a thing if your photo isn't properly focused. With today's autofocus systems, focusing is probably the least of your worries. There are certain situations where it's good to have a few tricks up your sleeve and know when to take control of focusing.

There are a few different types of autofocus (AF) modes in today's DSLRs. I'm not going to give a big rundown of all of the different names and types, but if you're interested, you can read this excellent blog post. For the purposes of this post, I'll be focusing on single point focusing.

For portraits, it's widely believed that a subject's eyes must be in focus. If you are shooting with a decent sized aperture, say f/5.6 and above, as long as your subject is in focus you'll probably get your subject's eyes in focus with any AF mode. When you start shooting at larger apertures, though, you'll need to be a bit more selective about where your camera focuses.

I shoot most of my natural light portraits at f/2.8. When you're close enough to shoot a head-and-shoulders portrait, the shallow depth of field you get is enough to easily lose focus on the eyes. That's why I always shoot in single point AF mode. Instead of letting my camera decide where to focus (which usually ends up being the tip of the subject's nose), I use one AF point (usually the center) and focus on my subject's eye that is closest to the camera, then recompose and take the photo. At extremely large apertures such as f/1.8 or f/1.4, I'll even move the focus point to the eye instead of focusing and recomposing, because at such large apertures recomposing can still cause the original focus point to be out of focus.

Another situation where it's great to take control of your focus points is any photo with strong backlight. Most AF systems work by detecting contrast and strong backlight can fool even the most advanced AF systems. By switching to single point AF, you tell the camera where to look and focus, effectively telling it to ignore the backlight and just focus on your subject.

Low light situations are similar to strong backlight. Because AF systems work with contrast, there is almost no contrast in a low light situation. Any little light in the background (maybe a candle at a wedding reception) can trick the AF sensors and throw your subject out of focus. Fortunately, by switching to manual mode you again tell your camera to ignore these little areas of contrast in the background and focus on your subject. In extremely dark situations you might even have to switch to manual focus mode, but that's an entirely different blog post.

Finally, don't just check the screen on the back of your camera and assume your photos are properly focused. Unless you're looking at images on a large screen at 100% size, it's almost impossible to tell if your camera is focusing on a subject's eyes or nose. Learn how your camera works and use that knowledge to get the sharpest photos possible.

Practice using single point AF. Practice moving your AF point around while you're shooting so that you don't always have to focus and recompose. Recognize which situations cause your camera's AF system to hunt for focus and learn to switch AF modes. Scrutinize your images at full size when you get home and see how they really look. With a little practice, you'll get sharper photos more often. You'll also be able to overcome challenges as they happen and get the shot that you want.

Here are a few examples of shots that I've been able to get with spot AF:

These two photos were completely backlit, which means I was focusing on their outline.  The fill-light on Jill and Mike came from my flash.

In this photo, even in spot AF mode, the camera still focused on the lights in the background.

Just a second later after recomposing and refocusing, I was able to get this shot.

Here's a strongly backlit portrait shot at a wide aperture.  By using spot AF, I was able to get her eyes nice and sharp.

Here's the original image...

... and here's a tight crop of her eyes.

Read all of my DSLR tips here.