The rise and fall of the digital SLR

During the latter days of film photography, almost every photographer used 35mm film, and almost every serious photographer used a 35mm film SLR. In the early days of digital photography the SLR was almost forgotten, only to make a huge comeback since 2003. There are signs that this is again to change. Why? This blog post will try to sum it up.

SLR is an acronym for “single lens reflex”, and means that the photographer physically looks through the lens by means of a rather complex mirror and prism setup. In the film days this was the only way to accurately show a photographer how his picture was going to look, since his eye was physically seeing the same image that was going to be projected onto the film when the shutter was pressed.

The complex path that light travels in a (digital) SLR camera

Compact “point and shoot” cameras had separate optical viewfinders through which the user framed the picture, but suffered from parallax error (especially when looking at close subjects), and could not properly show focus, depth of field or exposure.

A 35mm point and shoot camera

All of this changed with the advent of digital photography.

Even small compact digital cameras could show the exact image that was going to be recorded. (In fact, this was even more accurate than the image seen through many SLRs, since you actually saw what the sensor saw, including white balance and exposure.) Since the whole flipping mirror and prism was no longer required, digital compacts could also be made a lot smaller and cheaper than SLRs. Most importantly, 35mm digital sensors were very expensive to make, and therefore not able to compete with small-sensor compacts.

A simple small-sensor compact digital camera

Just how much smaller digital sensors were, compared to traditional 35mm film, is shown below:

Furthermore, by having a very small sensor (often smaller than the 1/2″ shown in the diagram above) allows a manufacturer to reduce the cameras power usage, and allows for very small lenses. The most extreme example of this is a cell phone camera which has a very tiny lens and sensor.

Then, in May 2000 things started to swing back in favour of the SLR. Canon announced the D30, its first dedicated digital SLR (DSLR) designed “from the ground up”, and selling for $3000. In August 2003 Canon extended this technical lead with the announcement of the Canon 300D, the first DSLR selling for less than $1000.

The Canon 300D (aka “Digital Rebel”) was a landmark in the evolution of the popular DSLR

DSLRs had the advantage of having much larger sensors than conventional point and shoots, which results in several advantages:

  • Much less image noise due to having larger pixels
  • Interchangeable lenses
  • More control over depth of field (i.e. nice subject separation by blurring fore/backgrounds)
  • Faster autofocus by measuring phase shift with a dedicated sensor, instead of image contrast detection.
  • Optical viewfinder with better resolution and no lag times compared to electronic viewfinders

But many of these advantages had nothing to do with having a mirror box – it was just an engineering hack. Large sensors used a lot of electricity and heated up quickly, therefore they couldn’t stay powered on the whole time, therefore you couldn’t have “live view”m therefore you needed an optical viewfinder.

There was no fundamental reason why one couldn’t make an interchangeable lens camera with a large sensor, offering (all) the DSLR advantages, but throwing out the old-fashioned mirror-box. Only temporary engineering hurdles stood in the way. That, and the fact that the established manufacturers like Canon, Nikon and Pentax had a legacy system with legacy lenses to support, and therefore opted for backwards compatibility. These legacy systems had the additional disadvantage of being mutually incompatible.

The logical step was to develop a interchangeable lens, large sensor, camera system which did not use a mirror box, but a smaller, simpler and cheaper direct-to-sensor design. And this is exactly what Olympus and Panasonic did with their micro-four-thirds system.

The micro four thirds system does away with the mirror box

The Olympus Pen and the Panasonic G1 and GF1 are the first cameras of this new generation, and are receiving good reviews. Even Samsung now joined the party with their “NX” system, which is basically the same thing as micro 4/3, albeit with a slightly larger sensor.

These cameras don’t (yet) match the performance of 35mm full frame models like the Canon 5D mkII, Nikon D3 or Sony A900, but nothing prevents the development of mirrorless 35mm cameras.

These new cameras offer the same functionality as DSLRs, minus for the optical viewfinder. However, Panasonic has a very clever LCOS digital display which reportedly does a good job as substitute, thus the lack of an optical finder isn’t as big as a disadvantage as it used to be.

Olympus hired Kevin Spacey to sum it up succintly:

Do these developments mean that it’s the beginning of the end for the venerable SLR? Not immediately in any case. But I expect that physics and logic will prevail, and that the enormous DSLR fad of the last 6 years will slowly subside. Putting sentimentality aside, the world no longer needs a mirror box. The guys behind micro 4/3 think progressively. I like it.