All You Need To Know About Auto Focus

An autofocus is an intelligent adjusting system of a camera that fine-tunes the lens to get a clear focus on the subject. This may actually be the difference between a prefect photo and what you may seemingly consider, a missed opportunity. Although the end goal is a simple, sharp focus, the fine inner details of how the camera focuses can be termed as anything but simple. However, with a clear understanding of the autofocus, you are in the perfect position to make the best out of it and avoid its limitations.

Autofocus Sensors

The sensors are the real mechanism behind the camera’s accurate focus. They are normally arranged in different arrays across the image’s field of view. Each sensor focuses on a particular part of the image thus it measures the point’s relative focus by evaluating any changes in contrast. Here, the maximum contrast is considered the maximum sharpness.

The Process of Auto Focus

1. The AFP (Auto Focus Processor) makes a significant change in the distance to be focused

2. The processor then reads the autofocus to evaluate whether the focus has improved. If it has, it calculates by how much.

3. The autofocus processor then sets the lens to a new focusing distance

4. Steps 2 and 3 may be repeated several times until the suitable focus is achieved.

Although the process sounds lengthy on paper, on an actual camera it takes a fraction of a second. If, on the other hand, the subject is difficult to focus, the autofocus gives up on the process and the result is unsatisfactory. This is what photographers term as “focus hunting” and it is highly dreaded. During focus hunting, the camera repeatedly focuses back and forth without quite achieving the focus look. However, it doesn’t mean that focus is completely impossible for the given subject. Some of the following factors might just be what is affecting autofocus.

Factors Affecting Performance of Autofocus

Three important factors highly influence autofocus. They include:

· The Level of Light

· The Subject Contrast

· The Camera or Subject Motion

Each of these factors are dependent on the other. What this means is that a better autofocus can be achieved if the selection of a focus point corresponds to a pronounced texture or a sharp edge.

Type and Number of Autofocus Points

The flexibility and stoutness of autofocus is majorly a result of the position, type, and number of the autofocus points that are made available depending on the model of the camera. High-end SLR cameras can have up to 45 or even more autofocus points while others can have only one autofocus point.

· Aperture

One important factor that autofocus points depend on is the aperture of the lens. The more the aperture, the more accurate autofocus will be. Try going for DSLR cameras with higher lens aperture even if you don’t intend to use the lens at its maximum aperture.

Numerous autofocus points are mostly reliable when they work together. Although, even if they work in isolation, they can still bring out improved specificity of the given subject.

Autofocus mode

Most cameras support the one-shot focus mode which also happens to be the best mode for still objects. However, for fast moving objects, it is quite susceptible to errors because it is not designed to anticipate object motion. On the other hand, most high-end cameras also support autofocus mode. This mode is best for fast moving objects because it adjusts moving objects’ focus distance continually. The science behind it is that it predicts the location of the subject slightly in the future, based on estimating the velocity of the subject from the previous focus distances it has captured.


The autofocus is the difference between the perfect shot and “just normal” photos. You want a camera with autofocus functionalities if you want to make it in the photography world.

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