Understanding focus in photography is crucial for every photographer. Without grasping the focusing tools a camera offers, you will likely miss out on images that could otherwise surpass the quality taken with any non-system camera. Important Information You Must Know About Focus
In this article, we look at the different focusing and area modes. Tools that provide you with everything needed to get the sharpest results from macro to sports photography.
- 1. What is Focus in Photography?
- 2. How Does Focus Work?
- 3. Focus And Depth-Of-Field
- 4. Focusing Modes
- 5. Auto Focus V Manual Focus
- 6. When To Use Manual And Auto Focus
- 7. Auto Focus Area Modes
- 8. Focusing with the AF-Back Button
1. What is Focus in Photography?
In any photograph, there is a plane of focus that sits parallel to a camera’s sensor. This plane is either in the foreground mid-ground or background and is the area in the image that is acceptably sharp.
By adjusting the focus either automatically or manually, you can change where this plane falls. Understanding how to focus correctly will lead to sharper images, or if used with the layering technique, create photographs with compelling depth-of-field.
2. How Does Focus Work?
Most modern cameras use their lenses to focus. This process happens when the complex system of optical elements inside the lens projects a representation of its field of view onto the film or sensor inside the camera body.
The point at which the light converges perfectly on the film or sensor will be the part of the image that is in focus.
A helpful analogy to understand this process is a magnifying glass burning a hole through a piece of paper. Here the magnifying glass is the camera lens, and the sheet of paper is the film or sensor. When the glass is too close or too far, the light passing through the magnifying glass will be too wide to burn.
However, when distancing the magnifying glass from the paper at the right length, the light will converge to a fine dot and burn a small circle. It is this point of light convergence that creates a sharp image on the sensor.
3. Focus And Depth-Of-Field
The point at which you set your camera’s focus will be the sharpest part of the image. However, the plane of focus will capture some space behind and in front of this point also.
It is possible to change the length of this plane by adjusting the aperture. For instance, you may want to use a narrow plane for portrait photography to isolate a subject while creating a creamy bokeh in the background. On the other hand, when shooting landscape photography, you will want to expand this plane as far as possible to make sure everything is in focus.
As previously discussed in the aperture article, the plane of focus will be short when using a large aperture or low f-stop number. Whereas it will be elongated when using a narrow aperture or high f-stop number.
4. Focusing Modes
In most modern-day cameras, you should find at least three different focus settings. These are autofocus-single (AF-S), autofocus-continuous (AF-C) and Manual focus (M). Each has its pros and cons, designed for specific styles of shooting.
4.1. Auto Focus Single (AF-S)
Autofocus single is an autofocus setting that allows you to focus on a single part of an image. In this setting, pressing the shutter button halfway will adjust the lens to focus. It will remain locked in the same position until pressing the shutter button down fully.
The AF-S option is a much faster way of focusing as the camera is not using any computational power to predict the movement of a subject. It is ideal for shooting stationary or slow-moving subjects such as portraiture or street photography.
4.2. Auto Focus Continuous (AF-C)
Autofocus continuous is the best option for shooting subjects moving at a moderate speed. This method of focusing is slightly slower than autofocus single because it uses computational power to predict the movement of a subject inside a frame and thus rearrange the point of focus. Furthermore, unlike AF-S, the camera will continually move the focus point when pressing the shutter button halfway.
4.3. Manual Focus (M)
Manual focus uses no motors or computers to help achieve focus in a photograph. When using manual mode, it is up to the photographer to use their skill to accomplish the correct focus in an image. It is advisable to use a tripod when shooting in this mode to help you obtain that pin-sharp focus in the areas that are required.
Furthermore, in some more modern cameras, it is possible to use a function called focus peaking. This setting highlights the areas of the photograph that are in focus with a colour of choice.
5. Auto Focus V Manual Focus
Once upon a time, it was necessary to focus every camera manually by twisting the barrel of a lens. Fortunately, technology developed, and the innovation of autofocusing emerged in the 1970s. This new technology meant that photographers no longer needed to rely on sheer skill to get a sharp image. Something extremely hard if not impossible to do for things like sports or wildlife photography.
The autofocus system inside a camera, controlled by a motor, makes the necessary lens adjustments to achieve focus when pressing the shutter button halfway. This system is much faster and more accurate than manual focusing in situations where subjects are moving.
Despite the ease of autofocus, there are still scenarios where manual focus is the best option. Macro photography, still life, and low light environments are examples of styles and situations where the manual focus still trumps.
6. When To Use Manual And Auto Focus
As a general rule, it is best to use manual focus for static subjects and scenes. This reasoning is because it requires a lengthy amount of time to adjust and fine-tune. On the other hand, single point focus is best for stationary or slow-moving subjects, and continuous autofocus is best suited for fast-moving subjects.
Before shooting, it is always important to ask yourself how much time you will have to adjust your point(s) of focus to compose your shot. The answer will give you a good indication as to which setting you should use. If you have a lot of time, then choose manual or single. If your time is limited, opt for automatic.
7. Auto Focus Area Modes
Modern cameras use what are known as autofocus points when shooting in their AF modes. These points cover the field of view inside the camera and range from roughly 9-51 points. Many cameras allow photographers the option to increase or decrease the number in a frame.
When using autofocus mode, the camera will be looking for contrast between these points to lock on to a selected area. Because of this, it can make autofocusing more challenging in low contrast and low light situations.
In addition to changing the number of focus points inside a frame, cameras also give digital photographers the option of how they wish the camera to use these focusing points. In one instance, it may be suitable to remain in total control and set an area manually. On the other hand, there will be times a photographer should hand over the decision making to the camera to achieve the best results.
7.1. Single Point
Firstly is the single point mode. This mode works by locking onto a single point of focus within the frame ad will remain stationary until moved manually by the photographer.
This type of area focusing is best for situations where the photographer wishes to focus on a specific part of a composition and has the time to be more precise with their selection.
7.2. Dynamic Area / Zone
Next is the dynamic area mode. In this mode, the photographer can increase the focus area to include multiple points. Depending on the camera, this can range from roughly 8-21 points. This area, like the single point, can be moved around the frame.
The dynamic area function is suitable when shooting larger objects or subjects in motion. There is an element of computational power that occurs in this mode. However, it only happens inside the area selected, which can be made smaller or larger.
Due to the manual element of this mode, it is suitable in situations where the photographer has the time to rearrange the area is necessary. Or can predict the movement of their subject and frame accordingly.
7.3. Auto Area / Wide
Lastly, there is the Auto-area mode. Unlike the previous two that relied on manual input, this mode is entirely automatic. While this may sound like an easy solution to selecting the focus peak manually, it is not without its faults.
Because this mode relies on detecting contrast to focus on what it determines as the most suitable subject, there is a chance that the camera will get it wrong. And the margin for error continues to rise as contrast dims in low light situations.
When shooting in AF-S, Auto Area mode is best at shooting sizeable subjects in well-lit environments, and there is not enough time to use the dynamic area function.
On the other hand, when used with AF-C, autofocus mode lets photographers track a subject in a frame. This mode is ideal for sports and wildlife photography when used with a continuous shutter and back-button focusing.
8. Focusing with the AF-Back Button
Whereas the traditional method of taking a photograph is to focus first by pressing the shutter button halfway down before pushing down fully to take the exposure, the AF-back button separates this procedure by focusing the camera when pressed.
This method of focusing is advantageous in instances where it is crucial to maintain focus on a subject while taking photographs. Because keeping the AF-back button held down, the camera will continue to track subjects inside a frame once locked. Whereas in traditional focusing, it is necessary to recompose the shot after making the exposure.
As you may have realised, there is far more to focusing than one may think, especially for people who have been used to taking photographs on compact and smartphone cameras. When faced with all of the options and functions of a system camera, it can seem slightly overwhelming at first.
However, don’t let this deter you, as once you have understood and mastered these, they will allow you to take photographs that far exceed the quality obtainable from a compact or smartphone.
Hopefully, this article has served as a valuable introduction to focusing on your system camera. It is now time to put the theory to the test and develop the sense required to use the appropriate settings. Start by photographing subjects moving at different speeds in each one of the focus settings and try out the area focusing modes in them. Do this in full auto mode, so you do not need to worry about any other settings. But take note of the readings from the exposure triangle.
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