The Problem with Viewfinders
Giving it that iconic shape, an SLR camera features a rectangular bump on top for the viewfinder. Yet no matter how integral to the shape and function of a modern camera it may be, the viewfinder is not without its history of problems. As we move into the mirrorless era, some things have changed, but not everything.
When the ancient Greeks first learned to project an image of what surrounded them onto a screen, they didn't need a viewfinder. It was literally "what they saw was what they got." As they changed the orientation of their "camera obscura," the projected image moved along with it. What they saw was what they got. Centuries later, when the camera evolved into a light-tight box with the recording medium ensconced inside, photographers had a problem. They needed a way to see what they were photographing.
To solve this problem, a second hole was added to cameras, parallel to the main taking lens. Photographers could look through this hole to see what was beyond, while maintaining a reasonable approximation of the camera's point of view. Fitted with appropriately tiny lenses, this "viewfinder" hole could provide enough field of view coverage to allow the user to compose a shot.
This solution wasn't perfect. No matter how close together the two optical paths were, the image seen by each would vary slightly from the other. It was like two people standing next to each other looking at the same subject. Of necessity, they saw their subject from a different angle. Technically, this distortion caused by a difference in viewing angle is known as "parallax," but knowing that didn't really help. Photographers could encounter unexpected surprises at the worst possible moments when their images didn't turn out with the perspective and composition they intended. There seemed no way to get around it. Two things simply can't occupy the same place at the same time. The best that could be done is to get the two optical systems as close together as practical, and deal with the imprecision.
After a few more iterations, enter the single-lens reflex camera with its pentaprism or pentamirror optical viewfinder. By employing the convoluted solution of a mirror that reflects the incoming image from a single lens upward into the viewfinder, but that was capable of swinging out of the way to allow a straight-through path to the recording medium behind it when the shutter release was fired, photographers could finally see things from the intended perspective. The two optical paths now shared a single entry opening.
Yet all was not completely perfect in the land of camera viewfinders. It seems nothing ever really is, now doesn't it. Even though the angle of view problem was now licked, matching the same framing and coverage still proved elusive. Typical SLR viewfinders were only capable of covering ninety-some-odd percent of what the final image would see. That left some margin around the edge of the frame hidden from view until the final image, and thus still some room for surprise. Achieving a full one-hundred percent coverage required a huge pentaprism that added significantly to the weight and cost of a camera. Only top-level professional cameras featured 100% viewfinder coverage. Everyone else just had to deal with it.
And this wasn't the only problem. Those of us who found themselves shooting in "awkward" situations such as close to the ground found it difficult to get our face and eye up next to the viewfinder to use it at all. At least from my personal experience, that was a problem. The solution for many years was the right-angle viewfinder attachment. Shaped as a tube bent like a capital letter "L" and containing a forty-five-degree mirror at the corner, I routinely fastened one to the built-in viewfinder so I could look down into it like an upside-down periscope. A tad ungainly, but it kept my face out of the dirt. Because of Nikon's annoying ambivalence as to whether they preferred round viewfinder attachments that screwed on or rectangular ones that slipped on from above, I've owned quite a few of these gadgets over the years. Annoying, but necessary. Again, speaking for myself.
But even this didn't solve everything. We photographers always want something more. In my case, the next major problem to be addressed was the difficult of keeping my face out of the field of view when shooting extreme wide angles. I can hear you thinking the lens should be pointed forward while my head should be either behind (with the viewfinder alone) or above (with the right-angle viewfinder attached) the camera, but a fisheye lens see more than many people assume. If you've owned one though, you know it, but that knowing this doesn't make it any easier to keep your head out of the way. Tripod legs manage to show up in the frame on occasion too, but that's a story for another day.
Some while after the film SLR evolved into the digital SLR (DSLR), a new option for such awkward situations became possible via the USB cable, or if you prefer, the HDMI cable. While not entirely convenient when shooting in the field, an LCD screen at the end of an electrical cable did finally make it possible to see what I was doing at a distance without worrying about where my head was.
Of note, this setup doesn't make use of the traditional reflex mirror viewfinder system at all. It relies instead on the electronic signals as read directly from the camera sensor. Ironically, this meant that, rather than the mirror being in the down position to see though the viewfinder and then swinging out of the way to shoot, it had to be held up out of the way for both viewfinder use and for shooting. That reflex mirror that photographers celebrated close to a century ago when the SLR was invented now became more of a problem than a feature in such situations. Eventually of course, the interchangeable lens mirrorless camera did away with the mirror entirely and plumbed the electronic signals up to the new electronic viewfinder (EVF), the same way as the USB and HDMI cables made possible to the external video monitor.
That's the way it works. Photographers perceive a problem, and camera makers work to solve it. Progress rules supreme. Or at least it tries to.
You see, technology and progress can't solve everything. One viewfinder problem remains, one that has been there since the very beginning and always will be. No matter how faithfully a viewfinder shows you what your camera and lens is seeing, and thus what your final image should record, it can't actually find views at all. It can only show them to you once you find them yourself. The truth is, the viewfinder has been misnamed all along. It's merely a "view shower," not a view "finder." You may argue that this distinction is merely a pedantic one, but in the final analysis, it's one that gets to the very heart of what it means to be a photographer.
The real problem with viewfinders is that they don't find views. At its heart, photography is about the view, and that's where we as photographers come in. Photography gear and technology may continue to advance, but some things never change.
I rather like that.