Often times, when you see modern smartphones with two, three, or even FOUR cameras, it has something called portrait mode. Portrait mode, in essence, attempts to mimic the natural effect (background blur) of large professional cameras, an effect generated by the presence of a “plane of focus” in which everything is perfectly clear and sharp and outside which everything gradually becomes blurrier and blurrier as the distance from that plane increases. Modern smartphones, to some extent, have the capability to do something like this with much smaller camera sensors, either through the use of additional cameras (like in the Samsung Galaxy S10) or the use of a single camera in conjunction with additional software (like in the iPhone XR) or split-pixel technology to simulate the presence of multiple cameras(like in the Google Pixel 3).
In order to recreate the background blur present in photos from larger cameras, a smartphone first needs to determine what the background actually is. In order to do this, multiple-camera smartphones(and the Pixel) use the difference in distance and depth between the images of the two cameras to help determine the subject of the photo. Often times, a standard camera is used with a zoomed-in telephoto lens to do the job. Those that don’t have multiple cameras try to do their best using software tricks. In either case. the camera software has been trained by the makers of said software to be able to more easily detect certain objects and subjects, namely humans and pets, and as such, portrait mode often works far better with these two things than with most others.
Once a distinct background has been identified, the phone applies a blur to it, and in some cases, some additional lighting and color effects to further separate and make distinct the subject of the photo. You may be thinking currently, “I could just go in and add the blur later with an app!” Most large cameras, however, do more than just blur the background with their natural depth-of-field effect, they also have the blur as a gradient, as I mentioned briefly earlier. As the distance from the subject becomes greater, the blur effect applied to the background becomes greater as well. As such, modern portrait mode-compatible cameras take that into account as well, applying a gradient blur, which is something you really couldn’t do with your free photo editor app, although the smartphone-applied blur does indeed look more artificial and less professional than the blur from a larger camera, with some mistakes here and there. But let’s be honest not very many people who aren’t pro photographers are going to want to take a full-frame camera with them everywhere.
And that’s the real beauty of portrait mode – not just that you can get a nice aesthetic with all your photos to put on Instagram, but the fact that you can do all that with a camera or camera array, that at most, is a little bit bigger than a large coin. Smartphone cameras have seen rapid advancements in the past few years, not just limited to portrait mode – features such as 240 \FPS slow-motion, high-resolution photos and videos, ludicrous amounts of zoom, and many others have graced phone cameras in recent years. The advent of more powerful photo processing in general, paired with the long-established trend of better camera hardware, have made phone photos a decent match for larger DSLR cameras, some of which may cost as much as the entire phone itself. Obviously, portrait mode has a long way to go and will undoubtedly go that way, but for now, it’s truly marvelous to see the leaps and bounds in the capabilities of cameras this small.
Author at STEMTalksNC