ObviousGuy's Journal: Why do Digital SLRs exist?

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!

Because

[Com2Kid]

Sometimes it is simpler to shove in a few mirrors with well known tech then to develop some sort of freaky ass projection system on to the view finder which would like uh totally suck. :)

Besides the bandwidth needs (yah lets design a bus to carry data all of like TWO FREAKIN INCHES!!) you'd be dealing with how to display the data in the view finder (really small LCDs, not enough real estate. Some sort of funky projection system?) and all in all, one would be inclined to ask;

why go through all the trouble when Nature has given us such an efficient data transmission system as it is? Namely, light! :)

Besides, there are always assholes like me who laugh at anybody without an SLR. :)

Easy solution, but psychological decision

[forged]

While I generally agree with the cruft that the system is, it is well understood by manufacturers and I don't see why the lens+prism system would become a major inconvenience even in the digital world.

If Canon or Nikon decided that the time has come to replace the flipping mirror by some direct CCD-->LCD association, they don't even need to modify their range of lenses or mount or bodies. All they have to do is to remove the mirror and replace it with some electronics such as a LCD viewfinder much like what already exists in camcorders for decades.

But it would feel a real loss to see this happening. You just cannot approximate the direct coloration, speed and precision of an optical viewfinder with a digital equivalent, no matter how brigh or how good the resolution would be. Especially for a long-time photographer. But that's entirely my feeling and I understand if people have a different idea...

BTW you really own a 1Ds...? Lucky bastard :)

Re:Easy solution, but psychological decision

[ObviousGuy]

BTW you really own a 1Ds...? Lucky bastard

I just play with it over at the camera shop across the street.

I almost own a Fuji S2, but luckily the coffee I spilled at the store didn't actually get into the demo camera.

Re:Easy solution, but psychological decision

[ObviousGuy]

The thing I think is that the medium itself is digital. Even with film cameras, what you see through the lens is just an approximation of what you will get on the film. The film itself will have its own properties that determine how sharp or grainy or colorful the pictures will turn out. Add to this that some lower-end dSLRs have a problem with viewfinder darkness (D-100 comes to mind), a bright colorfully lit LCD which displays exactly what will be saved into memory would be just what the doctor ordered.

You're exactly right about the camera bodies, of course. There's no need to replace the entire body just because the mirrors were taken out. But OTOH, an LCD viewfinder could allow for a larger eyepiece with a larger viewing area.

I don't want to pretend like this kind of technology is ready now. I've seen electronic viewfinders and they are not ready to be used in high-end digital cameras yet, but as the tech gets better and pixels get smaller and the pictures get sharper you will probably see the same switch from light to LCD that we are now seeing with film to digital.

I'm still saving my pennies to buy a Nikon FM-3a, so I'm hardly one to talk about dSLRs, though. ;-)