In this post, I will explain the different focus modes photographers can use to look for, shift and lock the desired focus point, regardless of the camera model (Canon, Nikon, Sony etc.)
What is the difference between AF and MF mode? Is manual focus better than autofocus?
The oldest mode, the easiest to perform and the hardest to get good results from is manual focus.
Manual focus search is performed by rotating the focus ring on the lens. When the desired focus point is reached the photographer stops the rotation movement and keeps the point locked by clenching his fingers on the barrel of the lens.
Manual mode was the only way to find and lock focus for many decades in the history of photography. In the past thirty years, autofocus systems have become more and more present in cameras, even in cheaper, mass-market models and recently they have become extremely fast and accurate.
Are there still situations when I would suggest to use manual focus? Not many but I can recall a few. These situations usually happen with tricky lighting conditions or when there are many physical layers in the image and some of them are thin or transparent.
When thin, clear, translucent objects or patterns are in between the camera and a clear, well-lit background, often autofocus systems skip them and place the focus further away, toward the background. Examples of these ignored layers include gates, windows, stems of flowers, tree branches, transparent structures, like spiderwebs, or thin lines, like wires.
Shiny surfaces, backlit objects or mirrors can sometimes throw the autofocus system off and place the focus point in the wrong place.
It is often hard to focus in low light conditions. If the subject is dark, with low contrast and it is fast-moving, again the autofocus might be unable to lock on and track its whereabouts. When the autofocus system of our camera fails at locking the focus in the correct place or at finding a focus point altogether, those are the times when we have to resort to manual focus.
What is the best focus mode for portraits? What is the difference between AF S and AF C?
Terminology to describe the behavior of autofocus systems can vary between camera models and brands.
The essence of it though is very simple. The autofocus system operates in a single shot (S) mode and in continuous (C) mode.
When autofocus is set to work in single-shot mode, it means that it performs readings and measurements, it locks a focus point and then freezes. As long as the shutter button is half-pressed the focus point, the focus distance, doesn't change. To change the position of our focus point we have to raise the finger and half-press the button again, to let the system take another reading and lock again.
This is the oldest focus mode. Autofocus systems started with this modality alone. Which is still great today.This mode is very accurate, it's fast, it rarely shows any hesitation.
The biggest foe of single-shot autofocus mode is the moving subject. If our subject is not still and we are not extremely fast at pressing the shutter button immediately after the focus locking procedure, the subject in the meantime will have moved to another area of the frame, closer or further, therefore out of focus.
With fast-moving subjects traveling toward or away from the camera, single-shot autofocus mode is a recipe for getting a lot of out of focus pictures.
What is continuous focus mode? How can I focus better on my DSLR?
In continuous autofocus mode, when we half press the shutter button the system places the focus point in a specific location but doesn't lock it. The system starts and keeps tracking the subject as long as we keep the button half-pressed.
This mode is great, as you can imagine, when our subject is moving because it ensures that when we are ready to fully press the shutter button and record the image, the focus point will be exactly on our subject.
Modern cameras use artificial intelligence as an extra feature to predict how and in which direction the subject will move thus increasing the tracking capabilities and the efficiency of the autofocus system.
The flaw of this system is that unless we can set and track an area of focus, which is commonly featured in mirrorless cameras, the continuous autofocus mode doesn't allow reframing.
The camera interprets the subject as the object or the person aligned with the focus detection point we have selected. If we change the framing of the picture a different object or point in space will be aligned and the camera autofocus system will start tracking that point, losing touch with the subject.
So if you use continuous autofocus mode and you're on a specific focus detection point make sure it stays aligned with your moving subject.
Continuous autofocus mode is the blessing of the photojournalist, the portrait, the wedding, the action photographer. With this mode, you can keep your eye in the viewfinder, follow the scene in real-time and press the shutter button when the time is right for you, without fear that in the meantime your subject has walked into an out of focus area of the frame.
The abundance of focus detection points and the enhanced tracking capabilities of mirrorless cameras allow the photographer to choose focus areas instead of points.
Focus areas let the photographer shoot in continuous autofocus mode without the need for reframing because as long as the subject stays in a specific area of the frame, the camera keeps on tracking it.
AI servo. AI focus.
With my current camera, the mirrorless Sony A7 Mark III I shoot with continuous autofocus mode 85-90% of the time.
Single-shot mode is still great with scenes where the subject is perfectly still and absolute focus accuracy is necessary.
With older or cheaper cameras who don't give us the option of focus areas but only points I suggest you use the central focus detection point in single-shot mode, lock the focus exactly on your subject and then reframe.
In most camera models, on the back panel, there is a button that can be operated with your thumb and that reads the following: AF-ON or AFL (these acronyms stand for Autofocus On or Autofocus Lock.)
What that button does is to lock the focus even if the shutter button is not half-pressed. It is very useful because locking the focus point allows the camera to set the exposure only after we have reframed, therefore performing a real-time reading on the effective frame that will be recorded by the camera. In other words, with this technique, we avoid the discrepancies and the exposure errors that happen when the captured frame and the one used to lock the focus are not the same.
In general autofocus systems are not perfect. Use them properly but in the end, trust your eyes. Your vision ultimately judges if an image, if your subject is in focus or not. Even with the latest cameras, the chance of an erroneous focus reading and focus detection is still real.
In difficult lighting conditions, when autofocus systems are tested, pay extra attention and if the images are important to you, take a few more shots, just to be safe. Out of focus images are hard, sometimes impossible to fix in post-production.
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