What is Focus?
Maybe I need a bit of a disclaimer before I begin what I have for you today. This piece will have numerous tips and techniques that include camera functions and features. But the focus, pardon the pun, of this work is YOU. It’s things that you can do, whichever camera you have, to up your batting average on focused shots. To come as close as possible to eliminating unfocused, unsharp images.
Focusing your camera better is an achievable task with a concentration on some details of your DSLR or mirrorless camera. You can increase your take of good sharp images.
To focus better learn and practice specific features of your camera. Focus modes, AF area modes, depth of field, and the exposure triangle are the areas of knowledge needed to better your focus and the production of great imagery.
Know your Focus Modes and How to use them
- Single Servo
- Full or Auto
- What Focus Mode should I use
Single Servo, Single, or AF-S
You received your first camera and opened the box. The shiny new camera had to be ready to go with the settings set as default by the manufacturer. The focus mode available on that day would probably be Single Servo or AF-S. Find the way your camera makes available your focusing modes. On my Nikon, I press a button on the side of my camera that makes the mode available on the top display of the camera for changes.
This is the mode primarily meant for non-moving subjects. Portraits, landscapes and general photography are easily focused with this mode. When the motion of your subject exceeds your ability to keep something in focus, consider moving to a continuous servo or AF-C.
You’ll notice that once you focus with AF-S, the subject moves before completing the push of your shutter button. A good example is soccer-playing children, which are always running.
Still subjects. Check your camera for two settings. First be sure you are on Single Servo, Single, or AF- S for focus mode. Also as a start, place the single spot (if that’s new to you, the appropriate lesson is coming very soon) in the middle.
Looking through the camera at something around the house you frame your first shot. Press the shutter halfway down and the focus is set on whatever the little box(es) is indicating. When you complete the pushing motion, you made your first shot.
So the first lesson today is the focus and recompose technique. Look through your camera and compose a shot. For sake of our lesson let’s assume the point that you want in focus is not where an indicator is. Without moving your position turn to place the focus point indicator on the element that you want to be the sharpest point in the shot.
Press the shutter button halfway down and pause there. While holding the button halfway turn to recompose the frame the way you intended to capture. When it’s all set, follow through pushing the shutter button down. You just made a shot with the focus, not in the center.
Continuous Servo or AF-C
Let’s move to motion. AF-C continues focusing as long as the indicator is on the subject, hence continuous. My camera has a button to lock focus so at any point you need to stop focusing, you can. So this allows motion to be tracked and keeps the focus on till you turn it off or pause it.
So, whether it’s fast-moving kids, or cars, or wildlife this AF-C setting is the best. Try it in combination with different autofocus area modes to get your best results.
Consider another lesson for keeping focus. Back button focus is using an ergonomically handy button to activate the continuous focus. On when you touch the button, off or pause focus when you remove your finger.
This back button technique, named because the norm is to assign a button on the back of the camera, even works well for still subjects. By activating to focus then removing one’s finger from the button to lock the focus setting. If there is a change in the focus distance just press the button again to re-focus and you’re done.
Full, Auto, or AF-A
Combining the features of both single and continuous to allow the camera to switch between modes as needed. On my Nikon DSLR, the focus starts when the camera is turned on and it will pause or lock focus when the shutter is pressed halfway.
In our world where AI, artificial intelligence, is growing rapidly let’s keep an eye on this camera feature as a tool that may be used more in the future. When descriptions include details like “the camera will decide which is the best approach to the following focus”, this may be the setting with more of a future. We’ll see.
What Focus Mode Should I Use
My suggestion is to learn by working with the AF-S mode and combine it with the different area modes (that lesson is coming up). Use the focus and recompose technique to get the focus where you want it. When you are comfortable with that and have a workflow that fits your photography, move to the continuous AF-C mode and see how that works for your photography. I use this as my default. If your primary photography is a moving subject, then you may need to move to AF-C quicker than, say, a portrait photographer.
Once you have a good understanding of AF-S and the focus and recompose technique; of the AF-C mode and the back button focus technique then step back. Think through your workflow with each and clearly one will shine as the best for you.
Know your AF Area Modes and the uses of each
- Single spot
- Group Dynamic
- Face, Eye or Animal Eye
- Which AF Area Mode should I use
What is the difference between focus modes and focus area modes? Focus modes are all about how the focus system works in focusing with a single touch or working to focus continuously. AF area modes are about the area of your screen or monitor, the real estate of your monitor, and how you direct the focus to your subject whether it’s with a single spot or a larger wide-area box. We are about to deal with dynamic area modes that track your subject within a given area of your future image.
It’s just what it says it is, a single spot. The earlier AF had only a single non-movable, then it advanced to 5 or so that were selectable. Technology now has cameras with over a thousand positions for the single spot.
Dynamic is the term I use for all the options that introduce some level of “intelligence” to the picture-making experience. Let’s look at some of my Nikon AF area modes and I think you’ll see what I mean.
Start with the first mode that covers 9 points on my screen. Focus is intended to be kept on the center of the nine. But, if you are following a bird or a basketball player and the single slips a bit. The surrounding 8 will come to help. So those 8 will dynamically “help” the center point to stay in focus. If the D9 setting is not possible because the subject has too much erratic motion, then there is a larger D21 and D51.
Other camera manufacturers make use of different size squares to do similar tasks. Normal may cover a size equal to 9 focus points, approximately, where larger squares cover closer to the whole screen. My Nikon has Dynamic 21 that is more equal to a medium square and 51 covers a much larger portion of the screen.
So be sure to learn about these dynamic features of your focusing system. This is a great set of AF’s to cut your teeth on releasing the focus and tracking responsibility to the intelligence of your camera, even though its only on a team basis.
My Nikon has a Group setting which gets a lot of use in my world. It is a set of 4 focus points. This feature goes back to a point in technology where the autofocus had a fault of focusing past your subject and focusing on the background. It’s very comforting now knowing that a photoshoot is no longer scarred by a number of images with perfectly sharp backgrounds and blurry subjects. The answer to that was to actually have a group of points each focusing separately and the camera focus distance would be set at the closest. Thereby, never focusing on the background.
Even though the early problem is pretty much corrected with newer technology I still like the feature and working with those 4 points. I looked for features on other cameras and did not see anything similar.
I list this as a separate topic but there are ways to activate it and you need to be sure to find ways to do it on your camera. My menu has settings to adjust how easily objects coming in front of my subject will take the focus. And become the new focused subject. It’s a kind of distraction control.
Some of the AF modes above work with tracking so realize to make the most of the feature, one must turn on tracking with the mode. For some, the tracking could be part of the area mode selection
Face, Eye and Animal Eye
The future is here. True autofocus needs to know what we want to be focused and for people and animals, it doesn’t get any better than this. When the camera comes to your eye and boxes appear that basically communicate “yes I know what needs to be in focus, this eye”. Yes the AF can be tricked if your subject is next to similar tones. It can be fooled but it is amazing how accurate it is and the future is bright for increases in accuracy.
Which AF Area Mode Should I Use
Stick with the basics. Start with your camera’s single spot AF mode. You may be taken by the auto nature of the camera selecting the point of focus but the need for correctly selecting the focus point based on your creative efforts. Remember, the viewer of your image is attracted to the sharpest parts of your image. This decision of the point of sharpest focus is a big decision and you need to select it yourself. Move to try out the others and learn the strengths and weaknesses of each.
The goal is to have a good working knowledge of each AF mode and AF area mode. The focus and recompose technique and the back button focus and to use the best for your photography. I know you may photograph many different subjects and the choices may be different for each.
You may find like I did, that certain combinations of features may work across different types of image-making. All this comes from experience. Enjoy the experience.
Learn the features of your Gear and the needed choices.
- Wider angle lenses have more depth of field
- More distant subjects have more depth of field
- AF system needs contrast/lines to give accurate focus
- Focus can be slow shutter speed motion that shows as blur
- Hold the camera correct
Wider Angle Lenses Have More Depth of Field
Yes, I was shocked. I knew the facts that we speak of here, depth-of-field, but I did not know the actual distances involved when we speak of more DOF or less. I use a calculator on my phone to make these calculations to the hundredth of a foot.
So if we’re shooting a subject that is 10 feet away and f5.6 is our aperture, we will have less than a foot of acceptable sharpness in our finished image if it’s captured with a 105mm lens. Change only the lens or zoom from 105 to 24mm, f-stop and distance remain the same. Our acceptable sharpness increases from 0.93 feet to 84.80 feet. Take a minute and see how lens selection changes the DOF in the following table. And how that change can be extreme.
|Depth of Field|
Granted, the changes made in a shooting situation would be much smaller. But to know that a zoom set at 50mm needs a bit more depth-of-field for a shot and all one needs to do is zoom back to 35mm (or step back) to add 6 feet of depth of field. From 4.28 to 10.13 feet.
As an example, when shooting larger groups, this could apply. Let’s say three rows of people in a group and previous work shows a bit of fuzziness on some subjects. Switching to 35mm, whether changing lenses or adjusting the zoom from the 50mm setting has a positive effect. 4.28 (50mm) feet could easily have some of the first or third row less than sharp. Changing to 35mm with nothing else changed changes our DOF to 10.13 feet. Score a much better photo.
More Distant Subjects Have More Depth of Field
This time we’ll leave the lens the same, 50mm. Check this! The distance to the subject will vary from 5 feet to 30 feet. Look over the variance of DOF, from approximately 1 foot of depth-of-field at 5 feet to 60 feet at 30 feet distance to subject.
|Depth of Field|
AF System Needs Contrast/Lines to Give Accurate Focus
Making your latest art piece and it has a massive amount of sky. No clouds or vapor trails. Beautiful graduated, rich blue sky. The autofocus has a hard time focusing. How do we solve this? Tilt the camera down to pick up some of the distant sailboats and BAM we’re focused!
So, remember that contrast or lines are required for your focus system to work. So when it starts hunting for sharp focus, it could be this. Move slightly to view an element of contrast, focus, then recompose.
Focus Can Be Slow Shutter Speed Motion That Shows as Blur
What are your limits? How slow can you go? Can you shoot at 1/15th second with a given lens? Does it require vibration reduction, image stabilization, or IBIS? Do you get sharp images at 1/60 second without any “help”?
Vibration reduction, image stabilization, and the king, in-body image stabilization are amazing features and can be a door opener for those borderline low light situations. Learn to use this feature and learn what your limits are to maintain sharp images. Also, look closely at your questionable focused images after a shoot to determine, was it focus or was I using a “too slow” shutter speed for this camera/lens combination.
Yes, you may be able to shoot with a physically smaller lens at 1/30th of a second, hand-held. But with your 70-200 lens the same speed is a guaranteed motion blur shot. Oh my! Its larger size is a detriment to making slow shutter speed shots. So take some time to determine the differences for you. What are your limits?
Motion blur cannot be fully discussed without touching on the use of the tripod. The tripod has the great side effect of throwing out all this dialog about which shutter speed to use to eliminate motion blur. So if you are on the border about using a tripod, this may be the time to make that move. I have three and make use of all three. It’s a size thing.
This wonderful journey, photography, is so much fun. Spending a day in a new urban area or hiking in the forest is so much more with the hobby or love of photography. Seeing things differently is all because of photography. My suggestion is to, at anytime, add to the joy a piece of the technology that needs to be mastered. So gather what this article talks about and take with you on your next outing some tech along with your gear and fire for this great hobby/profession. Enjoy