Dual Pixel Autofocus Explained

Dual Pixel Autofocus
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Dual pixel autofocus is a sensor based, phase detection autofocus technology which provides fast autofocussing and smooth, languid, gradually transient focus tracking when shooting videos and movies. Dual pixel autofocussing technology literally places in the hands of regular day-to-day users of consumer grade cameras the capabilities to shoot brilliant videos which look aesthetically pleasing and professional.

Okay enough with the definitions! Now let’s break this down….

Let’s start off with the name, “Dual Pixel”

Okay, let me start by saying dual pixel autofocus is just a fancy name for a technology that we have been using for long. Yes, this technology like all other technologies in the world has become better, but is not something that did not exist previously and is now made from stratch.

Remember Phase Detect Autofocus?

Dual Pixel Autofocus system uses the same phase detect autofocus technology, only in a grander scale and in a more sophisticated way such that the results are even better. Earlier cameras used sensors that had either of two functions, autofocus or imaging. The pixels on the sensor which were used for achieving autofocus and the ones used for imaging were mutually exclusive. In other words, each pixel was used for either autofocus or for imaging. NO pixel was used for both.

The number of pixels used for autofocus was considerably less than imaging pixels since no one wanted to compromise on image quality. Autofocus suffered a bit due to this.


How does it work?

Dual pixel autofocus eliminates the image quality versus autofocus conundrum problem from its roots. What this technology does is use each and every pixel on the camera’s sensor for both autofocusing and imaging. Each pixel has two photo-diodes (think of them as two separate sensors). When the photographer tries to autofocus on a subject, the camera reads the left and right photo-diodes independently and then calculates the phase difference of the two parallax images. Now the camera has enough information to instruct the lens to either focus further ahead or back and hence, achieve the perfect focus, fast….really fast. All this happens within a split second.

Dual Pixel Autofocus

As I said earlier, dual pixel autofocus is not new. It is just a new innovation based on the already widely used phase detect autofocus. The only difference now is nearly all the pixels are simultaneously used as both imaging and autofocus pixels; thereby improving autofocussing capabilities of the camera greatly, especially in low-light scenarios. Hybrid autofocus systems that allotted different pixels different jobs usually performed great when there was an ample amount of light. It really did struggle in low-light conditions where the phase detect autofocus couldn’t gather enough light to acquire focus properly.

Dual pixel autofocus makes transition of focus really really smooth and that looks absolutely beautiful and much better than conventional focusing. Pull focus (as on the Canon 70D and the newly launched Canon 80D) looks absolutely beautiful and professional. Not only does the transition look smooth and easy going; you can even select the autofocusing speed depending on your project and its needs.


Early users of Dual Pixel Autofocus:

One of the earliest DLSR cameras to use this technology was the Canon 70D. In the smartphone world, it was   Samsung S7 that had this feature built in, in March 2016.

Dual Pixel autofocus helps movie makers and cinematographers greatly. The ability to focus so precisely on a subject; then to track that subject as both the camera and the subject move with such precision is truly a game changer.

Resolution Chart Comparison

In a world which is fast moving towards 4K and 8K resolutions, camera autofocus assumes prime importance;  even more so because now it would simply be impossible to hide slipped focus anytime during shooting should it happen at all. The resolutions are so high and the details so pristine that even the minute differences and inconsistencies show through.

I sincerely hope this technology does really well and we photographers are gifted with even better, reliable and accurate focusing cameras in the near future.

Also published on Medium.