Bigger in photography means, faster, better, stronger (and more expensive).
Many people will say the only advantage of a digital SLR is that it gives you the flexibility of interchangeable lenses.
I think that’s bullshit.
If it was true, then the days of the dSLR are surely numbered—EVIL has arrived. EVIL, for those of you who don’t know, is an acronym so new, it doesn’t have a Wikipedia page yet. EVIL stands for “electronic viewfinder, interchangeable lens” and they are a new class of camera I’ll talk about another time. Suffice it to say, EVIL will not replace SLR photography—in the same manner that APS-C has not yet dethroned 35mm (much to my surprise). Besides, a lesser-performing EVIL camera costs nearly twice as much as the kits in this article.
I believe the biggest advantage can be found in its name: Single-Lens Reflex.
In order to have a single-lens design, in order to house a reflex mirror, the dSLR has to be big—and bigger, in this case, means faster, better, stronger (and more expensive).
Start with the sensor
Let’s start where all light writing discussions should always start: with the capture of that light—specifically, the bigger sensor.
ISO is a standardized measurement of light sensitivity. The higher an ISO, the faster the shutter speed. A bigger sensor means higher ISO. How? A bigger sensor gives more area (and more area per pixel) devoted to light capture. This means that the camera can be more light sensitive—so light sensitive that the latest professional Nikon D3s digital SLR is nicknamed “Lord of Darkness.”
But a bigger sensor is more than just faster, it’s also better. Better as in increased dynamic range because the electron wells behind these larger photosites means it can collect more charge and measure it more accurately. When you look at why Canon justified pulling out the RAW capability from their pocket-camera G7, you are still left with something factually correct—RAW in pocket cameras is almost pointless because there is no dynamic range embedded in the file that isn’t embedded in the JPEG processed image. We’ll see later that even the latest Canon G11, with it’s “large” sensor, continues to underperform the worst of these entry dSLRs and even the dSLRs of half a decade ago.
Also it means less diffraction, and less diffraction is better. A photographer should never forget the light—and light is both a particle and a wave. When it comes to diffraction, we are saying there is a point where the wave nature of light starts becoming important. On a 35mm camera, it dominates by an aperture of f/22, APS-C dSLRs grandfather in this hard-stop (though they should cut off by f/11). The more the megapixel or smaller the sensor, the sooner diffraction dominates. Most pocket cameras won’t even tell you how crummy they are stopped down and don’t think of blowing up your prints if they’re stopped down too far because all you’ll see is a smeary mess. Even if you don’t know physics, your eye doesn’t lie—an image taken by a dSLR is sharper and better.
Well, your eye does lie a little. The bigger sensor means that the depth-of-field, at the same angle-of-view is much shorter. Depth-of-field is a computation that covers how much is in focus—if you are a nature photographer you want to maximize it; if you are anything else, you want to minimize it. The physics behind this is due to off angle rays of light, but the understanding is simple: if less depth is in focus, then the part that is in focus will pop from the blurry background—and the easiest way to achieve this is with a bigger sensor.
In movies, production film has distinguished itself from amateur video mostly because the focus effect created by a reduced depth-of-field used by the larger imaging area. Similarly, the larger sensor in the dSLR uses focus to draw attention to the subject and give dimensionality to the image—and moreover, it says, “Yes, this photo was taken with an expensive ‘professional’ camera!”—and that is better than not that.
Think of it this way, a photographer tries to say something with a photograph by directing the viewer’s eye inside the image. One only has a limited set of tools: using the frame through composition, using the light, using a limited depth-of-field… I’ve shown how a dSLR gives the photographer better control of that light and the depth-of-field. Now about that composition…
Room in the box
The bigger size of the camera itself also means faster and better.
A bigger size means a bigger and brighter optical viewfinder. As fast as the processors in these cameras are getting, they’re not going to be faster than the speed of light—and an optical viewfinder gets the image to your eye that fast. As dSLRs get bigger, the viewfinders get bigger and brighter and become easier to use. As pocket cameras have gotten smaller, the optical viewfinder has moved to smaller sizes, become vestigial or simply non-existent.
The reflex mirror does offer a slight bit of blackout during image taking, but the delay between the shutter press and the acquisition, and the total blackout time is much less than on a pocket camera—and get’s even smaller the more expensive the SLR is. The dSLR responds faster to your finger and returns control back to you much faster than a pocket digital. Similarly, a bigger size means there’s room in the box for adding a phase-detection autofocus system. While there are other systems that can be more accurate, there is nothing faster.
Henri Cartier-Bresson once coined the term “the decisive moment” which means both the precise moment that the entirety can be contained in a single instant, as well as the ability to use a camera to capture that moment in a photograph. For better of for worse, the dSLR is currently the best device we’ve yet found to make reaching that decisive moment possible in the most situations—to capture a visibly arresting image within the frame.
Bigger also means more room to create a smarter autoexposure system for better images and drive demand for better optics. While there are better, sharper lenses, outside the dSLR world, it’s hard to imagine a better zoom lens out there. Even the universally panned kit zoom that is bundled with a typical entry level kit camera is still optically better than many SLR lenses sold in the days of film, and much better than any pocket camera’s.
Expense and strength?
Of course, that bigger size does come at a cost—to your pocket book. Remember as the size gets bigger, the weight goes up by a cubed… And the weight of your wallet plus the weight of your photographic equipment seems to be a universal constant.
(As for stronger? I suppose if I were caught in a dark alley, I’ll do more damage swinging around an all metal Nikon D3 with a 70-200mm f2.8 zoom lens attached than a pocket digital camera—then again, given the cost of the former, maybe not. Also people say I must be pretty “strong” to carry that all metal Nikon D3, flash, and flash bracket around.)
There is a place for everything
The best camera to have is the one you have on you
If you just don’t have the space-time for a dSLR, then you’re better off with your pocket camera.
The purpose of this section was just to point out that every design comes at a cost, and this is the price you pay for a small size.