Canon Autofocus Series: Getting Sharp Results, with Problem Subjects
April 4, 2019
There are times when it’s easy for pretty much any camera’s autofocus to grab onto a subject, and focus decisively upon it. Especially when using a digital SLR and focusing through its viewfinder, there are times the experience is simple and pleasant, and other times that can have you scratching your head, looking for answers.
Fortunately, as the digital SLR has evolved, the tools available to get good, sharp images have developed as well. Cameras like the EOS Rebel T7i (known as the EOS 800D or Kiss x9i in some parts of the world) and the EOS 77D (9000D) are good examples of cameras endowed with features that were frankly hard to find in mid-range cameras a few years ago.
In this article, we’ll look at some typical problems a user can run into, and show how the phase-detection AF available in today’s digital SLRs — and its benefits — can help you overcome some of these obstacles. And, you don’t need a top-of-the-line, professional camera to get great results…we’ll use the Rebel T7i and 77D as examples in this article.
PROBLEM: "I WANT SHARP FOCUS ON THE BACKGROUND, AND THE CAMERA KEEPS TRYING TO FOCUS ON SOMETHING IN THE FOREGROUND!"
Unless you set it differently, when you focus through the eye-level viewfinder, your camera will be in what Canon calls Automatic AF point selection. This means that all the focus points — 45 of them, in the case of a camera like a Rebel T7i — will be active. And, it means the camera will try to focus using the AF points that see the nearest subject with detail.
Examples of where this might happen:
Think about this scene, and what you might be trying to achieve. You might not have been at this memorial park, but you might be shooting something comparable. Maybe you’re photographing a group of people circled around a table at a reception, and the camera keeps trying to focus on something on the table, rather than your friends gathered further back, around it. Or, maybe there’s a distant landmark or building, but you have to include something in the foreground — and the camera keeps trying to focus upon that, instead of your landmark.
Here’s one more: you’re sitting at a stadium, watching a ball game, or perhaps at a theater, and want to photograph the stage. But in either case, the camera keeps trying to focus on the heads of the spectators in front of you.
The right tool:
Here’s where the AF Area control in a Canon EOS DSLR becomes a valuable tool. This puts you in control, as it lets you tell the camera where to focus.
- Be sure you are in the P, Tv, Av, or M settings on the camera’s Mode Dial. The “P” (Program autoexposure) mode is fine, if you’re a shooter who normally uses the full-auto Green Zone setting…this works similarly, except the P-mode lets you now have full access to all your camera’s menu settings, features, and so on.
- Press the AF Area button, on top of the Rebel T7i or EOS 77D. It’s marked with more little white dots on a small icon. Each time you press it, you change the number and pattern of possible AF points you can use.
- Keep pressing the AF Area button, until you arrive at Manual Selection: 1 point AF. You’ll now see one highlighted “box,” indicating that one AF point is active. By default, it’ll first appear dead-center, as shown here:
- You can now move that single AF point upward — or wherever else it would need to be, to cover and focus sharply on your main subject. Press the top AF Area button again, and then either press the upper Control Key button on the back of the camera (the four curved buttons on the Rebel T7i), or turn the rear dial (cameras like the 77D), and watch the AF point move upward. Stop when it’s where you want, such as here:
Tap the shutter button halfway to lock in your setting. Congratulations! You just did two things: you changed the AF system from simply using all its AF points and instead have told it to be selective, and to focus with one AF point. And, you moved that AF point to where you want sharpness in the picture. In the image we showed of the memorial marker, this is how you could get the sharpness you want, where you want — quickly, decisively, and without the camera trying to constantly focus on something closer.
What about if you’re using a Canon EOS model without the AF Area button? Press the rear AF Point Select button with your right thumb, and then turn the Main Dial (near the shutter button) until you see the single AF point you want to use highlighted in your viewfinder. Just tap the shutter button when you arrive there, to lock it in. Want to go back to Automatic AF point selection? Repeat the process, and stop turning the Main Dial when all the AF points are highlighted in the finder.
PROBLEM: "I WANT TO FOCUS ON ONE SINGLE SUBJECT, BUT I WANT IT TO BE WAY OFF-CENTER"
There are times when you want to put one primary subject or part of a scene way off to one side of an image, for a creative effect. But since the AF points in your viewfinder don’t cover the entire picture area, how can you focus on something that far off-center — like the roses in the picture directly above? The answer is easy: Focus Lock.
This is something you can achieve even in the full-auto Green Zone shooting mode, and using Automatic AF point selection (that is, you see the thin, black border lines surrounding the entire AF array in your camera’s viewfinder). It can also be done by manually picking a single AF point, as described above.
For simplicity’s sake, let’s presume you’re shooting fully automatically, and don’t want to manually choose one AF point yourself. Here’s what you’d do:
- Zoom your lens to get the desired composition, and if you need to, move forward or backward to get as much or as little in the viewfinder as you want.
- Move the camera temporarily so that your primary subject (in this case, the bouquet of roses) is in the center of the viewfinder.
- With the primary subject centered, press the shutter button halfway down to let the camera focus upon it. Do two things, as you do this: be sure a grouping of square-shaped AF points indeed does appear at this subject, and most importantly, don’t let up on the shutter button! Keep it pressed halfway down — this is what locks the focus, once the camera has initially focused upon a non-moving subject.
- With your finger still halfway down on the shutter button, move the camera to change the location in the picture area of your primary subject, such as moving the roses into the far upper-left of the sample picture shown here. Again, maintain that half-pressure on the shutter button — don’t let go of it!
- When you’re ready, without letting up on the shutter button, press it fully down to take a picture. If you then release your finger partially from the button, but don’t take it fully off, the focus will remain locked, and you can take more than one picture of that same subject, even changing camera composition to move it to different parts of the frame. Press fully again for each new shot.
PROBLEM: "HOW CAN I GET MY CAMERA TO QUICKLY FOCUS UPON A PERSON, EVEN IF THEY'RE NOT THE NEAREST THING IN THE SCENE?"
Many recent Canon EOS DSLRs can read skin tones, and actually help the AF system focus upon them in a portrait or other shot of a human figure. And, it’ll do this without leaving Automatic AF point selection, in cameras like the EOS 77D and Rebel T7i.
Examples of where this might happen:
Think of any time you have a portrait situation. Your subject may be centered, or off-center. Or, as we just showed above, it may be in a scene with other foreground subjects — closer to the camera. Automatic AF point selection by itself would tend to focus on whatever is nearest to the camera (as we explained a moment ago). With a portrait or candid-type shot, though, there’s another answer: use the color metering technology built into recent EOS digital SLRs, and let the camera choose to focus on your subject’s face.
It’s delightfully easy to do, when you’re using the eye-level viewfinder:
- You can be in any shooting mode, including the full-auto Green Zone, or even Landscape mode!
- In Creative Zone modes, like P, Av, or Tv, ensure you’re using Automatic AF point selection (you’ll see the thin border outline surrounding the AF Point array in the viewfinder). If you see one or more square AF points instead, press the AF Area button on top of the camera repeatedly while you look through the viewfinder, until you see the AF display change to just the thin, outer border lines.
- Compose and shoot your pictures! You’ll see that nearly any time a recognizable skin tone appears anywhere inside the AF array outlines, active AF points will be highlighted as you press the shutter button halfway down — telling you that this is where the camera is focusing.
What’s happening is that the metering system in cameras like the EOS 77D and Rebel T7i isn’t just seeing brightness. It can actually read different color values. And when it sees color similar to skin tones, it’ll usually detect this, and force the AF system to concentrate on those areas, even when they’re not the nearest part of the scene.
PROBLEM: "HOW DO I SHOOT MOVING SUBJECTS, LIKE BIRDS IN FLIGHT, OR SPORTS?"
There are several things you can do to tackle the sometimes-challenging topic of getting good, sharp pictures of moving subjects. You can do this even in the full-auto Green Zone setting on your camera’s Mode Dial, keeping the subject within the thin outer border lines you see in the viewfinder, and letting the camera automatically detect the subject’s movement, and then change AF points continually to keep it in focus.
But we’ll show you two different ways you can get even more potentially sharp shots of action subjects.
Using Sports Mode
The Sports Mode will immediately set your camera to continuous, AI Servo AF, so focus will expect movement, and work to keep a moving subject continually in focus. And, it simultaneously sets your camera to shoot continuous pictures, as long as you keep the shutter button fully depressed.
By default, it uses the entire array of AF points, inside the thin border lines you see in the viewfinder — and you’ll see one single AF point highlighted inside those border lines. This is where you want to start to focus, so put that point over your moving subject, and press the shutter button halfway down. Keep it pressed halfway — don’t remove your finger from the shutter button, unless you decide to re-focus on something else.
After a second or two, you’re ready to begin to shoot pictures. Just press the button fully down, and the camera will fire continuously. You can remove your finger if and when you want to stop firing the shutter, but again, if you keep partial pressure on the shutter button, the AF system will continue to keep focusing on the subject. This is an effective way to get a series of shots as a subject gets closer, such as the seagull in this example.
Using Zone AF, or Large Zone AF
The Zone AF and Large Zone AF settings change how many focus points are available. And, you can move them from the center of your picture to another area, giving you an additional level of advanced control. Either setting gives you a group or cluster of active AF points — none of the other, surrounding AF points are active, aside from what you see in your viewfinder. But this concentrated group of points provides more potential for sharp images of moving subjects, with less chance of some off-center foreground or background subject interfering with your continuous AI Servo focusing.
Zone AF and Large Zone AF are possible in nearly any shooting mode with the Rebel T7i and EOS 77D. The Sports Mode would be a logical first step as you begin to shoot action subjects. But for even more control, consider taking the next step, and changing the shooting mode to something like the Tv (Shutter-priority mode), and then dialing in a fast shutter speed like 1/500th (“500” would appear in the viewfinder, and on the exterior shooting display) or faster (higher speeds like 1/1000th of a second, 1/2000th, and so on).
Another benefit of using a Creative Zone shooting mode like Tv or Av is that you can deliberately lighten and darken your images, to compensate for things like large areas of bright sky in bird pictures, and so on.
PROBLEM: "I WANT TO GET GOOD, SHARP CLOSE-UP PICTURES, BUT MY AF SEEMS TO HAVE PROBLEMS PUTTING FOCUS EXACTLY WHERE I WANT."
Sharp close-up and macro pictures are always a challenge, even for experienced enthusiasts and professionals. And as good as the AF is on today’s cameras, sometimes it can become fussy and “hunt” back and forth when you focus extremely close, or it may put sharpness on another part of a scene.
This is one situation where you sometimes can actually get the fastest results — and sharpest ones — by temporarily turning off the autofocus, and pre-focusing manually. It sounds hard, but it’s really quite simple. Here’s what to do:
- First, zoom your lens (if it’s a zoom lens) to its longest, most telephoto focal length. You can do this at a wide-angle zoom setting, of course, but the most effective close-ups will happen with your lens zoomed to its maximum telephoto setting (55mm with a 18–55mm lens, 300mm with a 70–300mm zoom, and so on).
- Slide the AF/MF switch on the side of the lens to the “MF” setting. This puts the lens into Manual Focus mode. You can easily revert back to autofocus by sliding it back to the AF setting when you’re done taking close-ups.
- Pre-focus the lens’s manual focus ring, to set the lens to its nearest focus distance. (You don’t turn the zoom ring at all, from this point onward.) Some lenses have a small distance scale inside a clear plastic window, making this easy — just turn the ring and observe the distance numbers in meters and feet on the scale, and turn the focus ring until you’re at the nearest distance on the scale (lowest distance numbers). Stop at that point — you’re already at the lens’ nearest distance, and further rotation of the focus ring won’t make it focus any closer!
- To pre-focus a Canon-brand lens that doesn’t have a distance scale on the lens, hold the camera to your eye, and turn that manual focus ring clockwise (as you look out toward your subject, with the camera held normally at your eye) until the focus stops changing in the viewfinder. Again, leave the ring at that setting, and don’t turn it further; you’ve already got it set to the nearest focus distance.
Now, to actually shoot your pictures, just move yourself and the entire camera/lens combination, while looking through the viewfinder, until you see critical sharpness at the area of your small subject you want to be sharpest. Again, don’t turn any rings on the lens — you’ve already pre-set them to give you maximum close-up magnification. Just move backwards and forwards, be as steady as you can, and when you see the sharpness pop in the viewfinder, press the shutter button!
Of course, we can’t anticipate every possible question that may arise as you shoot pictures in challenging situations. But the good news is that even relatively low-cost digital SLRs today have AF options and controls to let you be the master in many environments, quickly delivering sharp pictures. Knowing a few basics, like how to lock focus on stationary subjects, how to change the size of the AF area and be able to focus critically on one part of a scene, and how to best handle moving subjects, will go a long way towards getting great results with your camera and lenses.
And, as we mention in the last point, sometimes even reverting to “old-fashioned” manual focus can actually be a quicker and more effective way of getting the shot you want. Modern autofocus is indeed a technical marvel, and a wonderfully effective tool for beginning and experienced photographers alike. Learn to make it work for you, and for the rare occasions where it may stumble, know how to get past any slow-downs by switching over to Manual focusing.