Phase detection autofocus is unmatched in speed. This method has a great ability to swiftly focus on erratically moving subjects, thanks to its lesser demand on computing power. The downside, however, is that as a result of the faster focus method, phase detection may not be as accurate as contrast detection.

While your aperture, shutter speed and ISO don’t affect how your camera focuses, they do play an important part in the sharpness and clarity of an image. This is known as the exposure triangle and it can be a photographers most basic, yet valuable tool.

In many applications, the required distance from an object and the desired FOV (typically the size of the object with additional buffer space) are known quantities. This information can be used to directly determine the required AFOV via Equation 2. Equation 2 is the equivalent of finding the vertex angle of a triangle with its height equal to the WD and its base equal to the horizontal FOV, or HFOV, as shown in Figure 2. Note: In practice, the vertex of this triangle is rarely located at the mechanical front of the lens, from which WD is measured, and is only to be used as an approximation unless the entrance pupil location is known.

Generally, lenses that have fixed magnifications have fixed or limited WD ranges. While using a telecentric or other fixed magnification lens can be more constraining, as they do not allow for different FOVs by varying the WD, the calculations for them are very direct, as shown in Equation 4.

There are two main AF systems used today and knowing which one your camera utilises is going to play a massive role in achieving perfect photography focus.

Single autofocus will lock onto a focus point and maintain this focus distance while ever the focus button is depressed. This focus mode is perfect for subjects and scenes that are known to be still.

Mirrorless cameras generally only use one detection method and up until recently, this was primarily contrast detection. But thanks to innovation, a hybrid system has been developed and is finding its way into many new mirrorless cameras. The idea is to obtain the speed of phase with the accuracy of contrast and as we keep progressing, this is proving to be an outstanding development in the camera game.

Manually focusing can be a tedious task as sometimes the smallest adjustments can make a massive impact. It is also much slower to accomplish than autofocus.

Shutter speed refers to how fast the shutter opens and closes in order to take the photo and, depending on what you’re shooting, the shutter speed can vary massively. Shutter speed affects focus mostly when shooting moving subjects. If the shutter is set too low, motion blur will become a major problem and render a photograph unusable. Whereas if the shutter is set correctly, you will get a tack sharp final image.

When moving onto high-end cameras, you will see an upgraded version of this type of sensor – the dual cross-type autofocus point. Basically, these are two cross-type points placed on top of each other with the benefit of contrast detection in 4 dimensions. This is massively beneficial when tracking fast-moving subjects.

Now we have crossed the line and switched to complete auto mode. With Auto Area Autofocus, your camera will scan your entire composition and select a subject to focus on.

Dynamic Autofocus utilises the best of both worlds in that the photographer chooses the point to focus but the camera will track the subject if it strays from said point. This is perfect for wildlife and action shots where erratic movement is to be expected. When it’s almost impossible to predict where and when the subject will move, utilising dynamic AF will increase your chance of nailing the shot.

While it may be convenient to have a very wide AFOV, there are some negatives to consider. First, the level of distortion that is associated with some short focal length lenses can greatly influence the actual AFOV and can cause variations in the angle with respect to WD due to distortion. Next, short focal length lenses generally struggle to obtain the highest level of performance when compared against longer focal length options (see Best Practice #3 in Best Practices for Better Imaging). Additionally, short focal length lenses can have difficulties covering medium to large sensor sizes, which can limit their usability, as discussed in Relative Illumination, Roll-Off, and Vignetting.

As time goes on and we continue progressing through the life of photography, I predict autofocus will be the number one choice on almost all matters. But that’s certainly not to say manually focusing is dead.

These points are commonly found in the centre of your camera’s sensor and will be more successful in tracking objects when compared to linear points.

Focusphotographyexamples

As with focus points, there is more than one autofocus system and they’re not all created equally. Certain cameras use different methods to achieve autofocus and each has its benefits.

Contrast detection generally requires more data to accurately focus, making the process work more slowly. On top of that, this system generally struggles to achieve any sort of focus in low contrast situations, such as low light photography.

Another way to change the FOV of a system is to use either a varifocal lens or a zoom lens; these types of lenses allow for adjustment of their focal lengths and thus have variable AFOV. Varifocal and zoom lenses often have size and cost drawbacks compared to fixed focal length lenses, and often cannot offer the same level of performance as fixed focal length lenses.

The idea is that you aim the centre point on your subject for focus but if your subject suddenly moves, the camera will track it to the outer focus points displayed.

Generally, dynamic AF is represented as a grid of focus points (mainly 9 points) with the centre point being larger, representing where the camera will focus.

Note: Horizontal FOV is typically used in discussions of FOV as a matter of convenience, but the sensor aspect ratio (ratio of a sensor’s width to its height) must be taken into account to ensure that the entire object fits into the image where the aspect ratio is used as a fraction (e.g. 4:3 = 4/3), Equation 7.

Linear focus points detect a change in contrast along a single dimension and can only sense in either the horizontal or vertical plane.

This mode is great for shooting still subjects, allowing you to set the focus point to exactly the desired location. This is ideal in photography styles such as landscapes and portraits, where the subject is predictable and steady.

Cross-type AF points detect a change in contrast across both the vertical and horizontal dimensions, making for a reliable autofocus point.

And while I would love to tell you I have the answers to eliminate this problem for good, I can’t. There are far too many variables that can create an unfocused photo.

Laugh all you want, but it happens! The clunk of the shutter actually made me physically jump, throwing my readiness to shoot, not to mention the quick blink can be detrimental to your aim if you aren’t ready for it.

The 14.25° derived in Example 1 (see white box below) can be used to determine the lens that is needed, but the sensor size must also be chosen. As the sensor size is increased or decreased it will change how much of the lens’s image is utilized; this will alter the AFOV of the system and thus the overall FOV. The larger the sensor, the larger the obtainable AFOV for the same focal length. For example, a 25mm lens could be used with a ½” (6.4mm horizontal) sensor or a 35mm lens could be used with a 2/3” (8.8mm horizontal) sensor as they would both approximately produce a 14.5° AFOV on their respective sensors. Alternatively, if the sensor has already been chosen, the focal length can be determined directly from the FOV and WD by substituting Equation 1 in Equation 2, as shown in Equation 3.

By relying on the camera to make the decision, you’re essentially adding another step to an already difficult and time-sensitive process. My suggestion is to make a judgment beforehand and select the appropriate mode, as in almost all circumstances you will know if your subject will be moving or not.

As you increase the ISO, you’ll introduce noise into your images which, in turn, creates an unwanted grainy effect. As you move into higher-level cameras, you’ll be able to push the limits of ISO higher and higher but as a general rule, you should keep your ISO as low as possible while still accommodating your other settings.

Autofocus is accomplished by the camera body and lens working together to drive the focus ring to the exact position it needs to be.

Achieving perfect focus in photography isn’t all about what modes to set you camera in, though that does take up a fair chunk of it. Your camera’s settings play an important role as well, just in a slightly different way.

Single point autofocus is the most honed in version, using just one single focus point from your camera. Having such a specific point gives the photographer almost every ounce of control over where the lens sets focus.

You’re not alone. I can almost guarantee that this has happened to every single photographer on this planet on more than one occasion.

Spot AF is about as specific as it can get and is an option for those wanting to ensure the camera is focusing on exactly the right location. For example, if you zoom in and focus on someone’s eye, spot AF will enable the option of focusing on a particular point of someone’s eye such as their pupil.

Another major factor in photography focus is what mode to choose. The key to determining the correct mode is to understand whether your subject will be moving or not, as this makes up 100% of the decision of what mode you should be in.

Compositionphotography Definition

A fixed focal length lens, also known as a conventional or entocentric lens, is a lens with a fixed angular field of view (AFOV). By focusing the lens for different working distances (WDs), differently sized field of view (FOV) can be obtained, though the viewing angle is constant. AFOV is typically specified as the full angle (in degrees) associated with the horizontal dimension (width) of the sensor that the lens is to be used with.

Example 2: For an application using a ½” sensor, which has a horizontal sensor size of 6.4mm, a horizontal FOV of 25mm is desired.

Note: As the magnification increases, the size of the FOV will decrease; a magnification that is lower than what is calculated is usually desirable so that the full FOV can be visualized. In the case of Example 2, a 0.25X lens is the closest common option, which yields a 25.6mm FOV on the same sensor.

Generally speaking, having a larger number of focus points in photography is considered better as this allows for more opportunity when composing a scene. However, it is a common misconception that a higher number of focus points is all that matters.

Back button AF is exactly as it sounds. A button on the back of your camera is used to activate autofocus, acting exactly the same as half depressing the shutter.

As you can no doubt guess, manual focus is the process of physically rotating the lens’s focus ring to achieve perfect photography focus. The process of rotating the ring shifts the plane of focus forwards and backward so you can set it to the desired location in your image.

Focal lengthphotography definition

\begin{align}\text{AFOV} & = 2 \times \tan^{-1} \left( {\frac{50 \text{mm}}{2 \times 200 \text{mm}}} \right)  \\ \text{AFOV} & = 14.25° \end{align}

Disclaimer: This post contains affiliate links. If you make a purchase of a product we recommend through one of our links, we may make a small commission at no extra cost to you! This helps to support our blog and enables us to continue providing you with helpful tips and exciting adventures, so thank you 🙂

We are Candace and Dylan, a couple with a flair for adventure and an inability to take life too seriously. Our passion for helping others and our desire to travel led us to create Tracks Less Travelled – a platform where we can share helpful guides and advice, and showcase our love of writing and photography.

But more than just creating a sharp image, when used properly, focus will draw the viewers’ attention to the exact point the photographer wishes to emphasise. Understanding where that point should be and achieving perfect focus is what makes the difference between a good shot and a great one.

So let’s take a look at the fundamentals of focus in photography and the secrets I have learnt that have helped improve my photography skills.

When we are talking about the differences between manual focus and autofocus, it’s important to remember these are both methods of achieving a common goal – perfect photography focus. The difference, however, doesn’t lie in the goal, but in the method used to reach it.

Honestly, I haven’t noticed any difference between single point and spot AF, and as a result, you can choose whichever tickles your fancy.

While most sensors are 4:3, 5:4 and 1:1 are also quite common. This distinction in aspect ratio also leads to varying dimensions of sensors of the same sensor format. All of the equations used in this section can also be used for vertical FOV as long as the sensor’s vertical dimension is substituted in for the horizontal dimension specified in the equations.

Not all focus points in photography are created equal and it’s important to know what type of points your camera uses and where they are located.

Honestly, single-point AF is the mode I use on most occasions, even in my mountain biking photography. It allows for exceptionally crisp shots and for me to choose exactly where I want the focus to be. But of course, this came with a steep learning curve and a lot of trial and error.

I definitely don’t recommend using Auto Area AF, I may be a little old school but I believe that with most aspects of photography, manual settings produce the best photos.

What is camera focus

Finally, the most important aspect of photography in general – the composition. While composition may not affect how your camera focuses, it’s the broader picture that’s at play here. If you compose your image correctly, it will draw the viewer’s attention to the exact point of focus, creating an effect that emphasises focus.

Once the required AFOV has been determined, the focal length can be approximated using Equation 1 and the proper lens can be chosen from a lens specification table or datasheet by finding the closest available focal length with the necessary AFOV for the sensor being used.

DSLRs are almost always equipped with both types of focus detection methods and accessing them is as easy as switching between the viewfinder and LCD display. The viewfinder will utilise phase detection, whereas the LCD switches to contrast detection. So it’s not just a coincidence that most sports and wildlife photographers shoot through the viewfinder, while landscape artists take advantage of the LCD screen.

There is a wide array of options that basically allow you to choose how much control you or your camera has over the focusing process.

Although most of the time photographers will revert to autofocus, manual focus still plays a massive role in the world of photography. Manual focus is a skill that is highly beneficial in circumstances where your autofocus system struggles and perhaps the most common struggle is shooting in low light. Autofocus systems need light and contrast to work effectively and when it is dark you’ll notice a serious lack of performance. Which will become immediately apparent if you plan on performing any night or astrophotography.

Honestly, I found this little button massively beneficial to my sporting and action shots. Trying to half-depress the shutter button nearly always resulted in a misfire, startling me and making me lose my subject.

You have the perfect position, the perfect angle, and the perfect frame. The subject of your photo moves into the screen and you snap the shot.

When using fixed focal length lenses, there are three ways to change the FOV of the system (camera and lens). The first and often easiest option is to change the WD from the lens to the object; moving the lens farther away from the object plane increases the FOV. The second option is to swap out the lens with one of a different focal length. The third option is to change the size of the sensor; a larger sensor will yield a larger FOV for the same WD, as defined in Equation 1.

I’d encourage anyone to familiarise themselves with this method of photography focus. For such a small adjustment, you can see massive results.

It will pay a great deal to understand the type of focus detection your camera has in order to maximise your success with accurate focusing.

These focus points are commonly found around the edge of your camera’s sensor, leaving the centre for the more accurate autofocus points.

As previously stated, some amount of flexibility to the system’s WD should be factored in, as the above examples are only first-order approximations and they also do not take distortion into account.

But moving onto the new craze in cameras – Mirrorless. Mirrorless cameras have been around a long time but only recently have they gained massive popularity. This is mainly thanks to advancements in focusing technology.

Technically speaking, focus in photography is the process of creating an area of rich sharpness and contrast in a photo, clearly defining the subject.

This hybrid system is known as Dual Pixel Autofocus and is being introduced into both DSLR and Mirrorless cameras. I have recently acquired the Canon R6 and, being equipped with Canon’s latest CMOS system, I’m blown away with the results for accurate and fast autofocus.

In general, however, the focal length is measured from the rear principal plane, rarely located at the mechanical back of an imaging lens; this is one of the reasons why WDs calculated using paraxial equations are only approximations and the mechanical design of a system should only be laid out using data produced by computer simulation or data taken from lens specification tables. Paraxial calculations, as from lens calculators, are a good starting point to speed the lens selection process, but the numerical values produced should be used with caution.

The focal length of a lens defines the AFOV. For a given sensor size, the shorter the focal length, the wider the AFOV. Additionally, the shorter the focal length of the lens, the shorter the distance needed to obtain the same FOV compared to a longer focal length lens. For a simple, thin convex lens, the focal length is the distance from the back surface of the lens to the plane of the image formed of an object placed infinitely far in front of the lens. From this definition, it can be shown that the AFOV of a lens is related to the focal length (Equation 1), where $ \small{f} $ is the focal length and $ \small{H} $ is the sensor size (Figure 1).

As you’ve probably guessed, hybrid autofocus is a combination of the above two photography focus modes. It works by allowing the camera to analyse the scene and determine which mode to use. While this may seem like a good feature, manually selecting your mode is a far better option.

The focal length of a lens is a fundamental parameter that describes how strongly it focuses or diverges light. A large focal length indicates that light is bent gradually while a short focal length indicates that the light is bent at sharp angles. In general, lenses with positive focal lengths converge light while lenses with negative focal lengths cause light to diverge, although there are some exceptions based on the distance from the lens to the object being imaged.

You’ll find different names for these modes across different brands (One-Shot, AF-S, etc…) much like any other menu item, but each camera will have a dedicated mode for this.

You may hear the term back button autofocus thrown around a lot and wonder what on earth people are going on about. For a while, I was confused about what this magic little button did, and what on earth the hype was all about.

These focus points work best when detecting contrast that is set perpendicular to the camera’s sensor and is the most common autofocus points. But while they’re the most common, linear points are generally the most limited and the least reliable type of sensor.

While phase detection may be less accurate on paper, the success rate is still very high – assuming you understand and implement all the steps of how to focus in photography.

You need to assess the depth of field you desire and set your aperture accordingly. Remembering lower f-stop numbers create a shallow depth of field while larger numbers increase sharpness throughout the entire image.

While autofocus systems are getting better and better, manual focus will always have a place and is a technique you need to master along your journey to mastering photography.

Like most other focusing settings, if you understand the exposure triangle and also the limitations of your camera, you’ll set yourself up for success.

Note: Fixed focal length lenses should not be confused with fixed focus lenses. Fixed focal length lenses can be focused for different distances; fixed focus lenses are intended for use at a single, specific WD. Examples of fixed focus lenses are many telecentric lenses and microscope objectives.

Field of view describes the viewable area that can be imaged by a lens system. This is the portion of the object that fills the camera’s sensor. This can be described by the physical area which can be imaged, such as a horizontal or vertical field of view in mm, or an angular field of view specified in degrees. The relationships between focal length and field of view are shown below.

Flash syncphotography definition

Continuous autofocus is perfect for any scene where the subject is moving. In this case, your camera will constantly refocus on the point selected while ever the focus button is depressed, which is perfect for tracking moving subjects.

Photography focus points are areas on a camera’s sensor that are sensitive to light and contrast differences. It’s thanks to these little dots that our cameras are able to quickly and accurately achieve focus. These points appear as empty boxes displayed on either your LCD or viewfinder, visually representing the points in which your camera can reliably focus.

Without getting into the science of it, your camera body will see the image, make a decision about where the focus should be, and then drive the focus ring to the correct position. Cameras are able to accomplish this task in a split second, a hell of a lot quicker than you or I. And that’s why autofocus is an extremely important tool in a photographer’s life.

When it comes to choosing between these two modes, you may find yourself at a loss. That’s because choosing how the camera focuses isn’t an option like most other focusing modes. Generally, the type of camera determines what detection methods are available and the main choice of camera these days is between DSLR and Mirrorless.

Proud of your set-up and confident you’ve nailed the shot, you call it a day. It isn’t until you’re back at your desk editing the photos that you notice the subject was out of focus.

If the required magnification is already known and the WD is constrained, Equation 3 can be rearranged (replacing $ \small{ \tfrac{H}{\text{FOV}}} $ with magnification) and used to determine an appropriate fixed focal length lens, as shown in Equation 6.

And frankly, it just looks so damn good! Nailing a perfectly in focus and crisp shot is one of the most pleasing feelings for a photographer. No matter which discipline, whether it be landscape, wildlife, action, or any of the other niches in photography, a perfectly focused image is far more appealing to the eye.

While having a higher number of focus points is beneficial, there is more to consider. Let’s look at the two different types of focus points that your camera may have.

Each area mode has its benefits and situation where it excels and understanding the difference will help you choose the correct autofocus area mode for each scenario.

Autofocus systems are complex and the settings are by no means universal to every photo you shoot. Below I’m going to go over the autofocus system and how it works to give you the best chance of understanding the art of photography focus.

Be aware that Equation 6 is an approximation and will rapidly deteriorate for magnifications greater than 0.1 or for short WDs. For magnifications beyond 0.1, either a fixed magnification lens or computer simulations (e.g. Zemax) with the appropriate lens model should be used. For the same reasons, lens calculators commonly found on the internet should only be used for reference. When in doubt, consult a lens specification table.

While this may sound great, more often than not your camera will get it wrong and choose a point you have no interest in making the subject.

ISOdefinition photography

In my experience, the camera will just focus on whatever is closest to the lens. This is hardly ideal for almost all scenarios in photography.

Now that we know what photography focus points are, we can move on to how to use them. The area modes refer to the number of focus points your camera will group together and use to focus on your desired subject.

Types of focus inphotography

This little miracle of a button can be found on most cameras and even if it isn’t, you can program another button to perform this task.

However, I can let you in on some of my secrets to drastically improve your hit rate and boost your confidence. And these secrets primarily come from having a strong understanding of the art of photography focus.

Zoomdefinition photography

Group Area or zone autofocus is similar to Dynamic AF, but rather than choosing a single focus point the photographer selects an area where they want the focus to occur. The camera will then use several focus points specified within the area and automatically focus on the nearest object within the area of focus.

Incorrect composition may lead to a distracting image with no clear focus point, which can take away from the sharpness of a photo.

Choosing the right point in the composition to use as your subject and focal point is extremely important in creating a clear purpose and avoiding confusion. This significantly helps to highlight the message you, the photographer, are trying to portray and can create a professional grade photo.

Knowledge Center/ Application Notes/ Imaging Application Notes/ Understanding Focal Length and Field of View

If you fail to set this correctly, parts of your image intended to be in focus may be blurry and vice versa. Aperture is – in my opinion – the most important setting of the exposure triangle and as a result, an important part of photography focus.

Phase detection doesn’t only work extremely fast, but it is far more reliable in low-light photography because the camera isn’t relying on a difference in contrast to distinguish the subject.

It does, however, get a little tricky when the subject is moving. If you take into consideration that the camera will constantly try to focus on where you direct that tiny little point (assuming you’re in AF – C mode), you can easily miss an erratically moving subject. There is no automatic subject tracking in single-point AF, adding to the struggle of capturing fast-moving subjects. Though this isn’t impossible, it is quite difficult and requires much practice and persistence.

3D tracking Autofocus is moving to the more automated side of photography focus. Basically, the photographer will select the subject by touching the LCD, or the camera will determine the subject automatically, and then the focus point will follow the subject anywhere in the frame without the need of panning the camera.

Contrast detection autofocus works by calculating a difference in contrast between the subject and the other parts of the scene. This method is tremendously accurate but does come with some shortcomings.

There is no point getting all of the above correct only to find you’ve missed the basics and so, I’ll run through these settings in order of which I believe your camera should be adjusted.

There is no shortcut to mastering photography composition and by no means is it easy. But with plenty of practice, you’ll develop a style and in turn, create masterpieces of your own.

Manually focusing in photography also comes in handy as a method of fine-tuning your autofocus. Sometimes your camera will get it slightly wrong and you can achieve the perfect result by fine-tuning the focus ring. This is particularly helpful for landscapes, portraits and any other type of static shot.

Basically, back button AF improves your control and steadiness over the camera as you pan and track moving subjects. It removes any chance of a false fire when you’re trying to aim the lens.

While this may sound great and seems to make dynamic AF redundant, it doesn’t. In many fast paced scenes, 3D tracking AF isn’t as fast or accurate as Dynamic or single-point shooting. And in some cases, It will confuse the subject with a foreground object.

This process is achieved by either manually moving the focus ring of a lens or relying on the camera’s autofocus capabilities to lock on to the chosen subject.

The aperture should be the first priority when determining your settings, as you need to decide exactly how much of the image you want in focus. Are you shooting an epic landscape where you want everything to be tack sharp, or are you shooting a portrait where a beautiful bokeh is desired.

Spot autofocus acts almost the same as single point AF with one minor difference, the focus point is slightly smaller. What you will generally see as the focus point is a square within a square signifying you are focusing on the smallest point possible.

You could argue that focus is the most important aspect of photography. A photo that lacks perfect focus will appear soft or blurry, resulting in the subject of the image blending in rather than standing out. But more than just a soft image, if you focus on the wrong point in the frame, you run the risk of completely losing the intended mood and subject of the shot.

ISO is a photographer’s worst enemy, but a necessity nonetheless. ISO refers to fake light created by the camera and is basically used to allow you to set the correct shutter speed and aperture. The higher the ISO the more light and faster you can set your shutter speed.

This is another very useful autofocus area mode for erratic situations such as birds in mid-flight or a lion chasing down prey.

Most modern cameras will incorporate face tracking or eye-tracking as part of these auto modes, which can be a massively desired function.