As regular readers know, in November I switched to Sony, replacing my 22 MP Canon 5D Mark III DSLR with the mirrorless 36 MP Sony a7R, plus three Sony lenses. My decision to switch had nothing to do with resolution and everything to do with the Sony’s image quality, dynamic range, and high ISO performance. Oh yeah, and the compactness of mirrorless. And after watching other DSLRs surpass the once upon a time state-of-the-art 5D Mark III, I just became tired of waiting through rumors. And when it finally came, Canon’s announcement of a 50 megapixel replacement for the 5D Mark III DSLR only validated my decision to abandon the company I’d been loyal to since the advent of my digital conversion, about a dozen years ago.
Doubt that I don’t secretly covet the 50 megapixels of the new Canon 5DS? Well, last month I put my money where my mouth is and purchased a 12 MP Sony a7S (more expensive than the a7R). That’s right, 12 megapixels—a pixel count that has been in the rearview mirror of most DSLRs for about eight years.
My a7R will remain my primary camera because it does everything I need it to do in most situations, and gives me extra resolution (I’m not opposed to more megapixels, I just don’t want them at the expense of the things I consider more important). In other words, if I can’t notice a difference, I’ll take as much resolution as I can get. But the best landscape images are often found in the most challenging light, so when the chips are down—like when I need extreme dynamic range or (especially) high ISO for low-light (moonless) night photography—I’ll turn to the a7S.
What’s wrong with more megapixels?
In digital photography, light enters through a lens, hits the sensor (which replaces the little rectangle of film we used to expose and develop), where it’s measured, digitized, and stored. Voila, a digital image is born.
Looking closer, we see that a sensor is an array of microscopic electronic light-catchers called “photosites.” On any given sensor, not all photosites are created equal (each one measures a specific color, either red, green, or blue), but for simplicity sake, it’s enough to know that one photosite equals one pixel—that is, a 36 megapixel camera has 36 million photosites, and a 50 megapixel camera has 50 million photosites.
A full-frame, 35mm DSLR has a fixed amount of sensor real estate upon which to place its photosites. Sensor technology continues to evolve, allowing more photosites and improved image quality with each sensor iteration, and spurring constant turnover as photographers chase the latest and greatest. But for any given technology, the fewer the photosites (lower megapixel number), the better the image quality.
The only ways to add more photosites to a fixed sensor area are to shrink the photosites, and/or cram them closer. Simply put, a larger photosite collects more light than a smaller one, making it more efficient. Think of a bucket: the bigger the bucket, the more water it holds before overflowing. And the farther apart the photosites are, the better they dissipate (heat is the enemy of pretty much all things electronic) and the less they interfere with the surrounding photosites.
There are advantages to a higher (mega)pixel count—larger prints, being the most cited benefit. A higher pixel count also increases the margin for error, allowing photographers to compose wide and crop later. But image quality is not one of those advantages, and in fact, the vast majority of photographers (including pros) don’t ever come close to needing the pixel count their cameras deliver.
Pro photographers have already figured out the inverse relationship between megapixel count and image quality. Look no further than the $6,000 Canon and Nikon flagship pro bodies to see that pro photographers hopped off the resolution escalator long ago: Canon’s 1DX is 18 MP; Nikon’s D4s is 16 MP.
Unfortunately, cameras are designed not for the expert minority, they’re designed for enthusiast majority. So until the consuming public figures out that they’ve been had, megapixels will continue to sell cameras, and camera manufactures will continue stuffing more onto our sensors.
Last week I got a firsthand example of the joys of low-resolution photography….
Seeing in the dark
I love night photography. While I’ve enjoyed and taught moonlight photography for many years, I’ve always been frustrated by the limitations of starlight (moonless) photography. Composition and focus are difficult at best in nearly total darkness, and getting adequate light into a moonless-night image usually requires unpalatable ISO and/or shutter speed compromises. But after hearing so many amazing things about the low light, high ISO performance of the 12 megapixel a7S, I just couldn’t resist (“Hi honey—uh, look what followed me home…”).
Last week was my first opportunity to use the a7S beneath the stars, at a favorite Yosemite night spot beside the Merced River. Given that I was leading a workshop, this shoot was not about my photography—the priority that night was (in this order) 1) Make sure no one walks into the river, and 2) Help everyone get at least one successful night shot. Nevertheless, I did manage to squeeze in a few frames of my own.
Bouncing back and forth between photographers in the dark, I occasionally stopped by my camera long enough to find a composition with the a7S and my Canon-mount 28 mm Zeiss F/2 (and the Metabones adapter). Jupiter was front-and-center, hovering above Half Dome, a focus gift for the group (finding focus in the dark can be a show-stopper for beginners). But rather than take the easy way out, I tried focusing on much less bright stars, just to see if it was possible.
I’m thrilled to report no problem focusing on even moderately bright, magnitude 2 and 3 stars by centering one in my electronic viewfinder, magnifying the view to the maximum, and dialing the focus ring until the star shrunk a fine point. What had taken a minute or two of effort on my 5D III, including multiple exposures to verify sharpness, took about ten painless seconds on the a7S (it didn’t hurt to have an f2 lens—this might take a little more effort if your fastest lens is f2.8 or f4).
Each time I visited my camera, I tried a different ISO/f-stop/shutter-speed combination. And while I’m not sure I got the most out of the a7S, I’m ecstatic about my results that night. I haven’t had time for extensive comparisons to determine the exposure combination that works best, but I learned enough to know that I’m going to love shooting with at night with the a7S.
I’m sharing here an image from that night, one I just pulled up and processed quickly. At ISO 12,800 is it noise free? Absolutely not, not even close. But at an ISO I wouldn’t have dreamed of with my Canon bodies, I found the noise pretty manageable and the results more than acceptable. And to fully appreciate what you see here, you have to understand how completely dark it was out there—to pull out this much detail from so much darkness is nothing short of miraculous.
Based on that one shoot, I think ISO 25,600 will be usable as well. I’m going to keep playing with it, trying to find the a7S’s ISO/F-stop/shutter-speed/noise-reduction sweet spot, over the next few months. I leave for Maui next week, but the moon will be in my night sky while I’m there. I’ll have have dark skies again at the South Rim of the Grand Canyon in mid-March, but the trip I’m really looking forward to is my Grand Canyon raft trip in May, when we’ll have no moon and some of the darkest skies on Earth. So stay tuned.
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