For the average person, focus refers to the parts of an image that you can see well versus the parts of an image that are blurred away! Focus is one of the most fundamental principles of photography, for showing your audience something you want them to see clearly is so important.
Achieving that focus is where the real challenge lies. It’s not usually as simple as point and shoot, you need to understand how focus works in order to make the most of it. From how focus impacts depth of field to ensuring your image appears tack sharp, here is our guide to focus in photography!
How Does Focus Work?
On a deeper level than what was mentioned above, focus is the process of achieving sharpness in an image. When something in a photograph is in focus, it’s the sharpest and clearest part of your entire image. Focus requires moving various lens elements until sharpness and clarity are achieved.
How focus works on a technical scale is very complicated, and truth be told, isn’t very useful knowledge for a photographer (it’s more useful for an engineer!). What photographers do need to know about focus is how to ensure you lock focus on the right subject.
When you focus your camera on a subject, it establishes a focal plane. To get your subject in focus, it has to be on the focus plane. Focus planes are imaginary horizontal or vertical lines. Anything that stands on the imaginary line will be in focus, and anything not on the line will be out of focus. This is how focusing works!
With modern equipment, the camera tends to take care of focusing for you. It shifts the proper elements inside of the lens in conjunction with the motors in a camera to make the camera lock on to your subject and focus clearly. Otherwise, you would manually turn the focus ring on a lens until your subject looks clear and sharp.
Depth of Field
You cannot talk about focus without also speaking about depth of field. Depth of field refers to how much of an image is in focus. When a depth of field is shallow, that tends to mean that just the subject is in focus and the rest of the image blurs away. When a depth of field is deep, both the subject, the foreground, and the background are in focus. This background blur is called a “bokeh.”
As such, shallow focus refers to a shallow depth of field and deep focus refers to a deep depth of field!
Depth of field is controlled by the aperture, which is described as a window in the lens that controls how much light does (or doesn’t) hit your sensor. This window depending on its width will also control the depth of field. A wide aperture (apertures that range from F/1.2 all the way to F/5) tend to have a shallower depth of field and the narrow apertures beyond that have a deep depth of field.
What you set your aperture to will directly affect your focus and your success at nailing focus, for shallower depths of field can be a bit more difficult to work with than deeper depth of fields. This is because with a wide open aperture your focus plane is very narrow. As you decrease your aperture number and make the opening wider, the invisible area in front and behind the plane of focus will get smaller and smaller. When shooting super wide open, like F/1.2, even the smallest movement out of the invisible line will cause your subject to be out-of-focus.
Keeping in mind how focus works can help you focus with shallow depths of field.
Like depth of field, it’s hard to avoid the question of sharpness when discussing focus. Sharpness is used to describe the clarity of subjects. When a photograph is sharp, the image is clear, filled with high details, and features a very lifelike (sometimes even hyper realistic) look.
You see, ‘sharpness’ as a term is actually an optical illusion. How sharp an image appears has a lot to do with contrast. If a subject is lacking contrast in the image, the subject will not look three-dimensional regardless of whether the focus is perfect or not. The way that our eyes work on a biological level requires edges to be detected by our vision. That is what registers sharpness. Shadows and highlights are there in order to record the depth of a subject.
That being said, on a technical level, tack sharpness requires accurate camera focus. Tack sharpness means the subject in an image is really crisp and clear in focus. This is achieved by ensuring that your focus is perfectly on the subject and not thwarted by even a little bit.
There are two different ways that modern cameras achieve focus, phase detection or contrast detection. Which one is used depends upon the camera and camera manufacturer.
Cameras have prisms inside of them. For phase detection focus, the picture you see hits the prism and then separates into two images. If these images line up together, this means that your subject is in focus! If they do not, then your subject is out of focus.
Phase detection is the more common type of focus that cameras use because it is fast and tends to be fairly accurate. Unfortunately, it of course can be prone to errors and misalignments, so that is something to keep in mind.
The second way that cameras focus is contrast detection. As the name implies, this focus relies on the subject (or whatever you want to be in focus) to be separated from its surroundings via contrast. Contrast detection does tend to be more precise because the focus system is directly measuring the data from your camera sensor to ensure that your subject is locked on. That being said, contrast detection is slower than phase detection because of the camera having to process so much data.
Tips for Nailing Perfect Focus Every Time
Which leads directly to the next point- how to nail perfect focus every time. Here are five tips to help you do that.
Tip 1: Know When to Use Autofocus and Manual Focus
Now, first and foremost, the easiest way to nail focus is to be aware of when you should let the camera do the work and when you should take control.
Autofocus is great for a large variety of situations, such as action photography, animal photography, portraits, and so much more. That being said, this is also greatly impacted by your autofocus mode settings.
In some conditions, autofocus may actually be to your detriment because the sensor cannot accurately figure out where the subject is located. This causes the lens to ‘hunt’, or move in and out searching for focus and not finding it. This happens with cameras that aren’t very adept at low light or subjects that lack contrast with its surroundings.
As such, switching to Manual Focus is the way to go here! Manual focus allotts the user full control over the focus, which puts photography right into your hands rather than the hands of a computer program. A trick to getting great at manual focus is to prefocus on the area your subject will be in, that helps you snap the perfect shot speedily.
Tip 2: Set the Proper Focus Mode
If you are using autofocus, then you need to set the proper focus mode for your shot to ensure accuracy. Cameras on average come in three modes: Continuous Focus, One-Shot, and a hybrid of both.
By default, your camera is set to One-Shot right out of the box. One-Shot achieves automatic focus on your subject for only one image, best used when capturing still life or product photography.
Continuous Focus is when the camera’s focus keeps refocusing on the subject as it moves. This is great for action photography and is how sport photographers are able to capture sequences of movements!
Automatic Focus means that the camera will attempt to decide between One-Shot and Continuous as your focus mode based on your subject and how you are using the camera. This mode is seldom used as it tends to not be accurate when picking out the focus mode.
Tip 3: Utilize Autofocus Point Selection
Every camera has a series of dots called the Autofocus Points. These points tell you (and the camera) where to focus. Each point refers to an area the camera is able to focus on. By switching to a mode such as AF Selection, you can tell the camera exactly what points you need it to use to focus on your subject!
The more expensive the camera, the more points there are, and the more accurately you can focus.
Tip 4: Check Your Proximity to the Subject
Sometimes your focusing issues may stem from something as simple as standing too close or too far away from your subject.
All lenses have a focusing distance, which refers to where the subject needs to be in order to lock focus. Lenses have a minimum focus distance (which is how close the subject can get to the lens) and a maximum focus distance (how far away the subject can be for the camera to ‘see’ it). Make sure that you adhere to the distances described for your lens!
As well, if you’re having trouble catching focus due to the depth of field, such as being very shallow, just move a little bit further away!
Tip 5: Use the Focus Lock Button
Sometimes your composition suffers when you lock on to focus. Use the Focus Lock Button located on most cameras and lenses to hold the focus on your subject as you move the camera around to achieve the right composition!
In conclusion, focus can be broadened to a complex series of technical specs and explanation, but for a photographer, all you need to remember is the focus plane and how to get your subject on it. With the above tips, that should become a breeze for you!