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What is a DSLR camera?

What is a (D)SLR? The Single Lens Reflex is so named because it has a mirror (and a single lens). But to really understand how the SLR got its name it’s important to go back to the days before it existed.

Before the [35mm] SLR became popular, there was the Rangefinder cameras (that used an optical viewfinder and a rangefinder mechanism to determine when the lens was in focus) and the Twin Lens Reflex camera (that had two lenses, one to view the image on a screen by way of a mirror, and a second one to record the picture).

Of course, both models are long gone now. Wait! We still have the rangefinder with us, courtesy of the Leica M9.

Leica M9 digital rangefinder

Leica M9 digital rangefinder

The Twin Lens Reflex (TLR), on the other hand, is long gone.

Rolleiflex, Twin Lens Reflex

Rolleiflex, Twin Lens Reflex

See Colbie Caillat in her music video “Kiss the Girl” using a TLR:

As good as the rangefinder camera was, it had one glaring problem: parallax, meaning that because the viewfinder was separate from the lens, the viewfinder showed an image slightly off from what the camera was actually capturing through the lens. This problem was compounded as you used longer telephoto lenses.

Parallax: You dont see exactly what the lens sees

Parallax: You don’t see exactly what the lens sees

To remedy this problem, camera manufacturers came up with an ingenious idea of putting a mirror in the path of the light coming through the lens. The mirror reflected the light up into the viewfinder compartment where it got reflected two more times inside a penta (5-sided) prism and came out through the viewfinder eyepiece the right side up and oriented correctly. When you pressed the shutter release button to take the picture, the mirror flipped up, out of the way, and the light proceded to expose the film (or image sensor in the case of a DSLR) behind the mirror.

Conventional DSLR with mirror structure, courtesy of Panasonic

Conventional DSLR with mirror structure, courtesy of Panasonic

Olympus OM-1 SLR

Olympus OM-1 SLR

This was hailed as a great progress since now the photographer could see exactly what would be recorded on the film — no matter what lens was used! Hence was born the Single Lens Reflex. It was pretty simple to name the new camera because it was really a Twin Lens Reflex that got a prism added on top and which used the same one lens (instead of separate lenses) to both view and record the picture. One lens only, so Single Lens Reflex (SLR).

The SLR was, of course, designed to be more than just a camera with a mirror inside. The mirror simply solved a problem, viz. how to ensure that the photographer could see exactly what would be recorded on the film.

But more than that, the SLR was introduced to be of a higher caliber than the rangefinder camera. It provided full exposure flexibility, was faster, more precise, better in many ways. And because the photographer could see exactly as would be recorded on film, the number and variety of lenses grew to encompass almost anything you may want your SLR to capture on film, from microphotography all the way to astrophotography.

When it comes to choosing a DSLR, it does not matter much which brand you choose if all you intend to use it for is point-and-shoot photography and do not intend to add lenses. If you do intend to buy more lenses, then it becomes very important to consider the availability of lenses (as well as other accessories) first; once you commit to a “system” it becomes very expensive to switch and so photographers tend to stay with the same brand for a very long time.

Nikon D3s System

Nikon D3s System

Now fast forward to today, where it is now possible for the photographer to see exactly what the image sensor will capture without the use of a mirror. The LCD screen (and electronic viewfinder) is now of high enough resolution to match the quality of the image viewed through the optical prism / mirror construct of a DSLR. With the redundant mirror now removed, is the resulting camera still a DSLR?

Digital Interchangeable Lens Camera, aka mirrorless DSLR, courtesy of Panasonic

Digital Interchangeable Lens Camera, aka “mirrorless” DSLR, courtesy of Panasonic

Let’s see.

D? Yes, it’s a digital camera.

SL? Yes, it’s a single lens camera.

R? No, there’s no mirror anymore, and that’s where certain people object to the use of the term “mirrorless” DSLR. It’s kind of an oxymoron.

So, how to call this new “DSLR” with no mirror?

Many have jokingly (and then seriously) referred to them as “EVIL” — Electronic Viewfinder Interchangeable Lens — cameras. That will never fly, in the marketing and any other sense of the way. Also, an electronic viewfinder is a given, so we don’t need to saddle the cameras with the “EV”. “IL” is the best choice, but I think we still need to differentiate between digital and non digital, so the “D” is still important.

Another proposal from Imaging Resource is the “SLD” for “Single Lens Direct-view”.

Olympus E-P1, Digital Interchangeable Lens camera

Olympus E-P1, Digital Interchangeable Lens camera

Since Olympus and Panasonic are the first to come out with these cameras, they dubbed them “Digital Interchangeable Lens” system cameras. Notice that they stopped short of using the acronym “DIL” — it does not sound as sophisticated as “DSLR.” Perhaps, if we spelled out the letters, like “D-I-L” — which does not sound that bad after all! Until a consensus is arrived at, we will refer to these cameras as DIL for now.

Panasonic Lumix DMC-GF1, Digital Interchangeable Lens

Panasonic Lumix DMC-GF1, Digital Interchangeable Lens

We expect that Nikon, Canon and other digital camera manufacturers will also introduce their own versions of the DIL, perhaps as early as this year or next year. You can be sure that their marketing people are currently busy running focus groups and trying to figure out just what to call these cameras. We need a name that everyone will readily adopt.

What do you think is a good name for the “mirrorless DSLR”, “EVIL”, “Digital Interchangeable Lens” camera?

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  • How about Digital Electronic Veiwfinder Interchangable Lens camera?(hahaha)

  • This is a pretty lame view of the history of camera design, in my opinion. The single-lens-reflex camera is actually older than the rangefinder, it’s just the prism that is fairly recent (the 1950 Contax S), and I would be hard put to find a SLR that “was introduced to be of a higher caliber than the rangefinder camera” before the Leicaflex of 1962, let alone “faster, more precise, better in many ways.” The Zeiss Contax system of 1936 (!) was capable of “microphotography all the way to astrophotography.” The SLR made it all easier, that’s for sure, but even today it is still inferior to a rangefinder in low-light wide-angle situations, aside from being much bigger, heavier and louder. This is my main beef with DSLRs by the way: why are they so big? If Pentax could make a film SLR as light and compact as the MX in 1985, why can’t we have a DSLR like that?

  • Spike, agree, the current DSLRs are just too big and heavy. Thankfully, we are starting to see smaller and lighter “DSLRs” or “DILs” on the way.

    BTW, I love the rangefinder, too, but can’t see a revival (except perhaps for the Leica M series). Even the Leica X1 uses Live View contrast-detect AF.

  • Since it is only the reflex that is gone: DSL

    (at the small risk of confusion with the popular internet standard)

  • Agreed! Since it is important to be able to differentiate between those that accept interchangeable lenses (Leica M9) and those that do not (Leica X1), we may have to add an “I” somewhere. 😉