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Do you want to understand your camera and take great photos today?

Yes Please

DSLRs are the standard, most popular camera choice by far. They are versatile and offer professional grade photographs (and video). They can also work with an array of different lens types. Models range from entry-level for those just starting out, to very expensive full-frame systems.

Whatever your budget, whatever your subject, a DSLR is a great choice of camera. But what does DSLR even mean?

DSLR stands for Digital Single-Lens Reflex. I can still see people scratching their heads, so let’s expand.

What Is an SLR?

The digital part we know, but the other parts are more confusing.

A Single-Lens means just that. The SLR that you photograph with has one lens, where the light will travel through to hit the film.

The digital aspect means that we no longer use film, but a digital sensor. They both work the same way, but having the digital version allows you to see the image almost immediately.

This might seem obvious, but not all cameras work with one lens. An SLR is an advancement on what is known as a TLR; Twin-Lens Reflex. 

A Nikon DSLR next to a Canon Single-Lens Reflex

What Is a TLR?

In the early stages of photography, cameras used glass plates, coated with a light-sensitive emulsion. The body of the camera held the glass plate and allowed you to focus the image. But, you couldn’t do both at the same time.

This caused numerous problems, and due to these, in 1870 the Twin-Lens Reflex was born. This revolutionary system allowed you to focus while the glass plate sat at the back. This was down to having two lenses; one to focus and one to take the picture.

These cameras would have a viewfinder on the top, which you look down into. These cameras were medium format, so their glass (and then film) measured either 6×4.5″, 6×6″ or 6×7″. The film used with these cameras today is known as 120 film, whereas the SLRs use 35mm film.

These Twin-lens cameras were a huge step in the right direction but created new problems. Having a different lens that you would focus with, and another to take the photograph was the problem.

The two different views would never match up, as one lens was above the other. For landscapes, this wasn’t really a problem, but the closer the subject, the bigger the parallax error.

A Rolleiflex medium format Twin-Lens Reflex

Parallax Error

A parallax is a difference in the apparent position of an object viewed along two different lines of sight. We have this in our eyes as there is a distance between our pupils, which shows each one as a different perspective. This concept is what helped camera manufacturers to create the SLR. One lens, one view, one perspective.

We know about SL & TL now, but what about the R? The Reflex is how we see the image – with reflection. Inside each of these cameras is a mirror that bounces the light from objects so that you can see them in the viewfinder.

The mirror in the TLR doesn’t move, but in the SLR, the mirror has to flick up to let the light hit the film. This mirror, set at a 45°, separates the viewfinder from the film plane. When the shutter is released, this is what forces the mirror out of the light’s path.

The inside of a Rolleicord showing parallax error

Image Credit: Images and Cameras


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These small format, 35mm single-lens reflexes entered the scene around 1920. It wasn’t until 1999 for the first DSLR to appear, from the camera manufacturer Nikon. It cost $6000 and had an effective 2.74 megapixels.

These digital versions still kept the mirror system, using one lens to frame and capture the subject. Today, almost 20 years later, you can buy a Canon EOS 5DS R. It costs $4000 and offers a whopping 50.6 megapixel resolution.

Benefits of a DSLR

The benefits of having an SLR over a TLR was that they were less bulky. Better lenses were created for the SLR, as some TLR didn’t have any zoom lenses available. The parallax error is a big problem when it comes to not seeing exactly what you are photographing.

Having a TLR does have a few benefits. Personally, I like the way it feels as it is a special camera that most people have never used. I use it for street photography, as it helps to keep my camera away from my face, which gives me candid photographs.

The advantages of having a DSLR over an SLR comes down to that D. The former is digital. This allows you to capture an image on a digital sensor instead of film. Photographic film is expensive, especially in relation to photographing multiple images.

With a digital version, you could take hundreds of photographs of a subject. The same amount of photographs with a film camera would mean many rolls of film. These take space, can be expensive to buy and then expensive to develop and print.

As long as you had the right adapters, you could even use the old analogue SLR lenses on your DSLR body.

If you are wondering which DSLR might be a good choice for you – read our article here.

The Canon EOS 5DS R DSLR

The Future

DSLRs may one day become a thing of the past. Twin-lens reflexes made way for their single-lens younger siblings. New systems are being researched and developed constantly.

One advancement in photographic technology has already created mirrorless systems. These are beneficial as there is no mirror action. This mirror flicking adds camera shake. Without it, we can take faster, quieter and better photographs.

These mirrorless cameras have resolutions that are quickly becoming comparable to DSLR cameras. They are lighter, more compact and have many lens options. Perfect for any kind of photographic need, from street to time-lapse photography.

For more information on mirrorless systems vs. DSLR cameras – read our article here.

Fujifilm X-10, a mirrorless camera system

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Craig Hull

Craig is a photographer originally from the West Midlands (go Led Zeppelin and Black Sabbath) currently based in Budapest. There isn't much photography he hasn't tried, but his favourite photographic areas are street and documentary photography. Show him a darkroom and he'll be happy in there for days. As long as there are music and snacks. Find him at and Instagram/craighullphoto