Let’s get one thing out of the way - full-frame cameras off better image quality than APS-C, Micro Four-Thirds, CX (1”) and smaller. Better low light performance, thinner DOF when you want it, better dynamic range (or exposure range as Ctein puts it), and so on. Sure the latest APS-C and Micro Four-Thirds may challenge an older full-frame sensor in some regards, but if they’re built with the same technology, full-frame is better.
Ah, but here’s the thing - it doesn’t matter. This set of charts that I just made will help explain my argument. Let’s start simple:
This is a basic plot showing how the image quality of all sensors are increasing over time. As you can see, sensor size is the primary factor in image quality, and everything generally falls where you expect it to. The green lines are stair-stepped to reflect the fact that progress is not a smooth line but rather is tied to the cycles of sensor development. Full-frame sensors, for example, aren’t updated as frequently as APS-C sensors. This leads to times where APS-C sensors size close the gap to full-frame sensors, but only until full-frame incorporate similar improvements. Please note that I didn’t put any quantitative scales on this chart. This chart is more about concepts, not definitive and quantifiable numbers.
Now let’s add another scale to the chart:
On the right, I’ve added an additional scale – Viewing Resolution – to put the idea of Image Quality into some sort of real world context. Simply put, the higher image quality sensors (which are invariable the larger sensors) are capable of more demanding output and viewing situations. Again, note that this whole exercise is conceptual; I am not, for example, claiming that you can’t make a nice coffee table book using photos from a Micro Four-Thirds camera. Also note that I’m putting aside issues of color gamut for the moment, as it’s not an area where I feel like I know enough to write about. I’d welcome feedback on this topic.
If I’m not making any claims, then why is it there? Wait for it...
That yellow line is why. The yellow line describes how we as a society are progressing from paper-based photographic media to digitally-based photographic media and how digital media is currently at lower resolutions than print-based media. You’ve heard the stats about how many photos are taken every year these days and how the sheer quantity overwhelms whole decades of photo taking. Well guess what, a vast majority of today’s photos are viewed on phones and laptops and tablets that have comparatively low resolutions to what we are used to in good print reproductions. Think about the flood of images that you encounter in your own daily lives – how much of it exists at 300DPI? How much of it, ultimately, requires a full-frame camera, and how much of it can you look at (without peeking at the EXIF) and say with certainty, “That’s from a full-frame camera.”?
If our viewing habits were not changing, or better yet, improving, then maybe there'd be a strong argument for full-frame cameras. But they're not. We're inundated with imagery, and we spend less time with each, pausing only briefly before we click next. Within this contemporary context, just how important is full-frame? Now the newest iPhones and iPads as well as a number of Android devices have "Retina" style high resolution displays; that's why the yellow line tilts upward somewhere in the future. Digital display technology is improving, and that at some point, even high resolution “Retina” style displays will be supplanted and HD will be supplanted by 4k video and 8k video.
“What about high ISO?” you may say, “Full-Frame cameras have the edge there and always will.” That’s true, but over time, that edge will apply to an ever-diminishing set of real world circumstances.
Finally, what about the Full-frame vs. APS-C debate? You know the one, where the mythical $1500 full-frame camera falls from the sky and exterminates all the APS-C cameras? We might see if that pans out soon enough with the deeply discounted Nikon D600, but I suspect that APS-C DSLRs will survive. Had this $1500 full-frame camera arrived five years ago, when APS-C was struggling to shoot a clean ISO 1600, then this doomsday scenario might have played out, but APS-C cameras are so good these days - for just over $500, I could buy a Pentax K-01 and a 50mm F1.8 and shoot clean ISO 3200 in the dark. But I’ve been wrong once before; there’s always a second time.
We’re not there yet, but at some point in the future, someone with a 1” sensor camera (as found in the Sony RX100 and Nikon 1) will be able to use a slow kit zoom and snap a shot of their lovely newborn asleep at night. It will be clean ISO 51200 or whatever and more than good enough for showing on their iPad 15. On that day the ISO war will be over. How far in the future? I’ve got no idea. Ask Sony. But at that point in the future, how many people will need or want a full-frame camera. Even if it costs $500 at that point, it’s still going to be bigger and heavier and require bigger lenses and a bigger bag.
At the end of the day, this is another take on the sufficiency argument. Someone else on the Internet recently said (and I’m paraphrasing here), “In the history of camera formats, the smaller format always wins.” That’s oversimplifying a bit, perhaps, but there is some truth there; the most popular camera right now is the iPhone after all.
That said, I’ll be the first in line for a Pentax K-02 with a full-frame sensor. I just want it, and want is a powerful thing.
[This is the first post in a series. The second is "The Case Against APS-C". The third is "The Case Against Micro Four-Thirds"]