You can break down the history of photography into two eras: pre- and post-smartphone. Reductive? You bet. But from a numbers standpoint, it's not giving enough weight to the post-smartphone era, since FAR more photos have been taken in the last few years than in the preceding 200.
It’s become common to say that mobile phones killed the digital camera...but it’s also not likely. A digital single-lens reflex camera can obviously do a lot that your phone never can. But it can also do a lot that your phone was meant to do, but better. If you want to ramp up your Insta-game, a pro camera might not be as daunting to the newbie as you think.
The advantages of cell cameras are easy to see, but...
Digital cameras turned photography from a relatively niche pursuit, with each shutter click bringing a substantive cost of money and time, into something far cheaper and easier, and smartphones finished that trajectory. Smartphone cameras are always around us, and are essentially weightless -- most phones wouldn't be any smaller without them, and would just have slightly higher battery life. Download shots to a computer? It already *is* a computer. Process? Meh, just click a filter. The act of photography became as simple as breathing, and thus it became nearly as ubiquitous.
This transition happened so fast that you can almost hear the camera companies say "Disrupt us? We aren't even finished disrupting film!" The bottom has dropped out of the market for tiny-sensors in handheld compact cameras that offered fewer and fewer benefits over the phone cameras everyone was already carrying. But there is still a large, devoted user base for large-sensored cameras, particularly with interchangeable lenses, and for good reason. As a professional photographer who takes hundreds of thousands of photos a year, I would love to say that we can all just stop buying so much gear and use our phones, but that day is still the realm of science fiction.
But why, you ask? Look at what cell phones can do now -- the photos are clean and crisp! With multiple lenses like the iPhone 7+ you can even create a shallow depth-of-field effect previously associated mostly with professional cameras. Won't these software geniuses eventually bridge the gap?
The benefits of DSLR only look like disadvantages
Let's set a standard for discussion -- some mad scientist could always put a cell antenna in a Hasselblad and say that this article is null and void. When I say "cell phone camera," I mean the ones that are small enough that the phone still looks like a phone…not like, say, the Leica C1, a camera that can make phone calls. With that stipulation in effect, there is one thing that cell phone cameras will never do, no matter the software… and that's be large.
Wait, isn't small size an advantage? Sure…mostly. But it has a lot of drawbacks too. For all the tech improvements, a camera is basically a box with a hole in it, and what matters most is the light that enters it. It's the "photo" in photography. And when you take a 35mm frame like on my Nikon D5 or less expensive cameras like the Canon 6D, that hole is 28.7 times larger than on the iPhone 7, letting in that much more light.
Lightweight cameras yield dark photos
The most obvious way this affects images is in low-light quality. Remember, the makers of large cameras have their own geniuses improving them too. Often, they work down the hall from each other. (Hello, Sony sensor juggernaut!) So while cell phones have gotten better and better at turning indoor locations into something decently recognizable, large-sensor cameras have gotten INSANE at low-light.
You’ve probably seen the ISO level on your phone’s manual settings. ISO represents the camera’s sensitivity to light, and as it increases, you can take shots in darker conditions. The tradeoff is visual noise: your photos will look more like they’ve passed through a dust filter.
Even good phones turn to extreme noise reduction by the time they hit ISO 800. On a 1-inch sensor camera like the Sony RX100, you can take passable photos at ISO 6400. On the D5, if you're willing to use cell-phone level noise reduction, you can shoot decently at ISO 100,000 (or nice and crisp at a "mere" 20,000 or so).
It used to take Stanley Kubrick modifying NASA lenses to achieve images brighter than the human eye. Now you can do it with pretty much any recent DSLR and even a cheaper f/1.8 prime -- indeed, the limit in dark situations tends to be what your eye can see, which is where Live View (using the LCD as a viewfinder) and electronic viewfinders come into play.
But all this extra light and area has some less obvious benefits as well. Some of them are pretty technical (we won’t get into the math of lens diffraction), but one that is readily apparent is dynamic range. The human eye is pretty good at making out detail in light and dark situations at the same time -- when you look at a shadow in midday the sky doesn’t turn blindingly white in compensation, but in digital cameras it tends to.
But more and more cameras are better, at least after processing, in faithfully reproducing all the shadows and highlights of a scene into a tone curve. Cell phones that can shoot RAW file format can achieve better dynamic range through processing, but doing so tends to accentuate the already higher levels of noise in the darker areas.
Phone software can mimic DSLR, but brings new problems
Another basic physical fact happens when you make a sensor larger -- you gain more control over depth-of-field, the ability to focus on objects a certain distance from you and blur objects at other distances. This can be approximated through software effects but those still come with all sorts of limitations -- one focal length, a strange focus halo around the subjects, or varying accuracy -- whereas with a larger camera it’s just how things are.
There are other advantages you aren’t likely to see on cell phones due to how awkward they would be -- extensive mechanical controls, for instance. It was a leap forward in functionality when phones allowed you to take a picture with the volume control switch, giving you one button that you could operate the camera with tactile feedback. At a quick count, the Nikon D5 has at least 37 such controls, many of them extremely customizable. With these, an experienced user can operate the camera, getting ready for the shot that is about to happen, without ever having to look at the camera. And since photography is about predicting the moment, not reacting to it (since it’s too late!) it’s an invaluable addition.
Most phone camera features inadequately mimic DSLR functions
The flashes on cell phones aren’t actually flashes in a real sense -- they’re tiny flashlights. A flash is a quick release of energy -- sometimes as fast as 1/100,000th of a second -- that allows a much greater light output with less power required and heat generated. Not only are they stronger, but that fast triggering freezes motion even when the camera has a low shutter speed, opening up a slew of opportunities for capturing action. For now, at least, this alone opens up an entire photographic world that can only be approximated by even the best cell phone cameras.
Lastly, to maintain size, there are only certain kinds of lenses that you are going to see. Adding a real optical zoom increases size, and you’re not likely to see a 28-300mm equivalent lens on anything that looks like a phone any time soon, at least without additional clip-on lenses that reduce optical quality to some extent. You’re not going to capture far-off birds in flight, or shoot a soccer kick-off from the sidelines.
I don’t even need to say that you can create an amazing photographic portfolio using only cell phone cameras -- countless people are out there doing it right now. But there will always be areas where it just pays to go bigger, particularly when looking at technically difficult fields like low-light action. Technically, interchangeable-lens photography is already a niche, due to the staggeringly high number of smartphone photos. But it is a rewarding, irreplaceable niche rightfully loved by millions, and it’s not going away anytime soon.