I've been doing a lot of thinking about cameras lately.
I wasn't ever a big camera freak until I came to Japan. It all began a few months after I got here. You see, my wife is a web developer who doesn't like being restricted to clip art catalogs, so for one of her projects we went out and splurged on a Fujifilm FinePix F601. It's a sweet little camera with recording up to 6 million pixels and a really nice zoom lens. It's quiet, small, and feature filled. It's also discontinued in the U.S., probably because it's too expensive and fills a niche that doesn't really exist.
Since getting that camera, the photo bug has bitten me. I spend way too much time at the camera store across the street from my office handling the various 35mm SLRs[1], consumer digital cameras, and professional dSLRs[2]. It's a lot of fun for an otaku like me, even if the wife doesn't understand my obsession.
Something has been bothering me about cameras, though. As I was playing with the Canon Ds which is arguably the best mobile digital camera on the market today[3] I began to wonder about dSLRs. The reason that SLRs exist is to fix the problem of parallax that plagues rangefinder cameras. Rangefinders are the 'normal' type of camera. They can be the cheap one time use throwaways or they can be several thousand dollar Leicas with interchangeable lenses. No matter the type or maker of rangefinder, though, they all suffer from parallax. Parallax is the difference in angle between what is seen through the eyepiece and what is seen through the lens and ultimately projected on the film. At large distances parallax is not an issue because the lines of sight eventually merge into one, but at very close distances the difference in angle can be very great. What you see through the viewfinder may not be visible through the lens.
SLRs were designed to fix this specific problem by showing through the eyepiece the same image that will be projected onto the film. The image you see looking through the viewfinder is actually coming through the lens system, not approximated like in the rangefinder camera models. This is achieved by placing a system of mirrors and prisms between the lens and the film which redirect the incoming light upwards, away from the film, and onto a screen in the viewfinder. When the photographer presses the shutter button, the mirror is flipped up blacking out the viewfinder for a moment [4] and letting the light coming through the lens hit the film. This flipping makes the well known "ka-chak" sound that is music to any photography otaku's ear.
Camera bodies have evolved around this mechanism and lenses have grown up with the evolving camera bodies. Nikon and Canon have vast selections of lenses available for their cameras both first party branded and third party branded. When making the switch from film photography to digital photography the cost of lens replacement is a real issue. Having bought into the Nikon or Canon lens system means that half of your decision of which digital camera to buy has already been made.
Camera manufacturers have been basing their dSLRs on SLR camera bodies. It makes sense because these bodies are already in production and can be tweaked in minor ways to support electronic imaging sensors instead of 35mm film, in addition photographers are already familiar with SLR bodies and are usually comfortable with them. So for very little effort, traditional camera makers can become digital camera makers with a ready-made audience dying to upgrade to digital.
But is the digital SLR necessary? The point of SLRs was to eliminate parallax by giving the photographer a true TTL[5] image in the viewfinder[6]. However, with current digital imaging technology it is possible to have a TTL display projected into the viewfinder electronically without any need for a mechanical system of mirrors and prisms. Many "prosumer" model cameras like the Fujifilm FinePix S602 eliminate the SLR mechanism and provide a TTL image by transmitting the image to an LCD display in the eyepiece.
Fuji and other manufacturers of similarly-equipped cameras have given the user an SLR experience without the worries of owning a real SLR. In the current state of the art it is still troublesome to see great detail in the LCD viewport, but such problems will likely work themselves out as LCD technology gets better[7]. The other big problem is that existing lenses are not compatible with these new high-end consumer cameras. Expensive modifications and fitting rings need to be attached before they can be useable with normal 35mm lenses, and even then there is no guarantee that things like autofocus will work and play well with the digicam. This seems to be a deliberate crippling of these models by the camera manufacturers to encourage professional photographers to pay a couple thousand dollars more for the 'professional' line of dSLRs.
So I wonder what the benefit to the consumer is of the dSLR camera body. It definitely offers the benefit of essentially unlimited photography in a familiar film SLR body, and it has the added benefit over 'pro-sumer' electronic TTL viewfinder cameras of a wider array of lenses and peripherals. However, neither of these are true benefits if the so-called pro-sumer cameras could be made to support existing lens systems.
It is my belief that at some point the reliance on mechanical imaging via mirrors and prisms is going to bite camera makers on the butt because some radical upstart is going to make dSLR-quality cameras without the SLR cruft and earn a large foothold in the digital camera market. Such a camera would be useful to the weekend photgrapher who wants an easy interchangeable lens system and to the professional photographer who can't afford to spend money and time waiting for the repair shop to fix the stuck mirror. Technology is the only limiting factor here with the LCD display, but betting against technological improvements is a losing bet.
[1] SLR - Single Lens Reflex cameras
[2] dSLR - Digital Single Lens Reflex cameras
[3] Kodak will likely take this title soon, and Sigma should have a serious contender with Foveon technology.
[4] Many digital cameras will black out the screen during a shot to simulate this SLR action.
[5] TTL - Through The Lens
[6] The cynic in me says that it was also to have more things to break and drive up profits from repairs and warranty sales.
[7] Foveon promises good things on the light-receiving components. Could this tech be turned around and used as a display component. This would increase resolution by 9 times per each square inch. Dibs on the patent!