Autofocus: Phase Detection and Contrast Detection


The performance of your camera greatly depends on the focusing system it employs. The type of autofocus system you desire is one of the first things you’ll really want to consider when searching for the perfect camera. It is crucial to understand how it functions.

Additionally, it should be mentioned that when it refers to autofocus performance, cameras and lenses work cooperatively. Many applications, including barcode scanners, information kiosks, and industrial robots, whose operating distance is dynamic use autofocus cameras. By dynamically adjusting the position of the lens, autofocus is a feature that is used to take the sharpest possible picture.

Since phase detection and contrast detection autofocus are the two techniques utilized in contemporary digital cameras, understanding their differences is also beneficial. Let’s discuss to comprehend two distinct autofocus detection features.

What is Phase Detection Autofocus?


Phase detection autofocus is a method of autofocus that makes use of such phase shift information.

A portion of the light reflected off a subject pass through the main mirror and into a smaller sub-mirror when using phase detection autofocus. The incoming light is instead split into two distinct beams by the extra mirror, which bounces each beam downward. Depending on where the light beams land, a sensor near the bottom of the camera may then determine a subject’s distance. The sensor eventually activates a motor that handles the lens’s focus.

Phase detection is significantly quicker than searching for the focus, therefore the lens can autofocus in a millisecond since it can estimate the focus instead of searching for it. But compared to contrast-detection AF, this technique is more expensive and bulkier.

But it’s vital to remember that phase-detection systems can get misaligned and behave differently depending on the lens. You might need to spend some time adjusting your camera’s focusing system while stepping out into the field.

What is Contrast Detection Autofocus?


Contrast detection autofocus, as the name implies, finds focus by analyzing the contrast between the edges of your scene, while the lens changes the point.  It is the most basic and precise form of focusing technology. This makes it the most affordable autofocus technology.

When we are using unassisted manual focus, our brain probably operates in a manner like this: we stare at edges and adjust the focus ring when the edge contrast seems to be the highest. By analyzing the difference between the pixels on the camera’s sensor, this detection moves the lens back and forth until it finds the ideal focusing position. The topic is in focus when the contrast is at its peak. Therefore, there are no independent images, comparisons, or predictions with contrast detection autofocus.

Despite all the benefits of contrast detection, this procedure is time-consuming which results it is the slowest method.

Contrast Detection vs Phase Detection Autofocus

Contrast detection autofocus is smaller, less costly, and, at least on still targets, more accurate than phase detection autofocus. The contrast-detection AF is substantially slower, which requires time to calibrate, making it unsuitable for fast-moving subjects, compared to phase detection.

Phase detection systems can determine the precise adjustments that must be performed when the light rays fail to align. Phase detection autofocus is very quick because this is accomplished in a matter of milliseconds.

Contrast detection autofocus’ precision is by far its most significant advantage. Due to the fact that contrast detection analyses data from the imaging sensor, it is very rarely inappropriate.

You can experience persistent misfocusing if the dedicated phase-detection AF sensor and the dedicated imaging sensor were not in alignment.

If you want to stick to portraits, landscapes, or still photography, contrast detection AF is the way to go. Phase detection AF is better suited for sports and wildlife photography, especially in continuous shooting mode.

Cameras using hybrid autofocus systems, which combine phase and contrast detection focusing, are becoming increasingly widespread. Typically, hybrid AF systems begin with phase-detection AF to immediately focus the subject before transitioning to contrast detection to sharpen the edges for the sharpest possible output.

Which is Preferable?

Phase detection and contrast detection were both developed in order to deliver high-quality photos with precise subject focusing. Both of them have advantages and disadvantages. The use of autofocus applications makes it hard to distinguish which of them is preferable.

For still-life and high-contrast scenarios

Contrast detection autofocus will deliver the most accurate focus while shooting single-shot autofocus with a static subject. As with phase detection, there is less chance of the camera focusing in front of or behind the object. When employing contrast detection, you should be aware of this phenomenon known as front or back focus.

Make sure, however, that contrast detection autofocus requires more movement from the lens motor. This suggests that it will consume more juice. A slower motor will also be necessary for larger lenses with more glass components. Focusing is useless with moving objects, as it really requires a long time for contrast detection to find the ideal contrast.

By the time the largest contrast point is located, the subject has already moved to another distance, and the camera must once again locate that spot. Phase detection autofocus will rapidly move the motor to the ideal focus position for continuous shooting.

In low-light and low-contrast situations

Just remember that the focus of each of these technologies depends on light. The camera might not have enough information if the image has low contrast or brightness to use either focus method. There are alternatives. The ISO will be raised whenever a subject passes by or is visible in front of the embedded camera. When the focus is achieved, the light is intensified, and the camera’s ISO value is restored.

What is Hybrid Autofocus?

Hybrid Autofocus will be promoted by some cameras. Phase detection autofocus and contrast autofocus are combined to create hybrid autofocus in a single camera.

The quick phase-detection autofocus method is typically the first step in hybrid autofocus. After using phase detection to get close, It uses contrast detection autofocus to refine the edge, which doesn’t take as much time as it would ordinarily. Thus, phase detection brings it back to the sharp focus that our eyes notice, while contrast-detection goes even further.

Wrapping Up

The handling of a camera is a little bit easier when autofocus is used.

The concept of autofocus can become very complicated. It demands a depth of technological knowledge to completely understand it. The fundamental ideas are summarized in this post. You should be better able to comprehend how various autofocus systems operate, as well as the advantages and disadvantages of each kind. If you are still confused with the concept, we (Vadzo) can assist you with your needs and our support team can bring you suggestions for an autofocus camera, if you need that for your next projects.

Please find the list of Vadzo Auto-Focus cameras:



If you’re ready to talk about your camera needs, Vadzo’s team will be happy to assist you.

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