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DSLR camera (Digital single-lens reflex camera)

Written by: Nate Torres

Last updated: September 30, 2024

I have grown to love DSLRs, but as I’ll touch on later, they might not be as popular as they once were. Let’s explore what these cameras are, how they work, advantages and disadvantages, and why they aren’t as popular as they used to be...


What is a DSLR camera?

DSLR stands for Digital Single-Lens Reflex, and is a type of digital camera that stands apart from other digital cameras due to its mirrored reflex design scheme.

That was a mouthful, so let’s look at each term to get a better understanding.


What does DSLR stand for?

Digital

The first term is “digital.” This means DSLR cameras do not use film and instead use digital sensors to capture images.

A camera digital sensor.
Camera digital sensor

Before DSLRs, we had film cameras called SLR cameras which stands for “single-lens reflex.”

An SLR camera.
SLR camera

So you add on the letter “D” for digital, and they started calling these new cameras with digital sensors DSLR cameras.

DSLR vs. SLR camera.
DSLR vs. SLR camera

Single-lens

The second term is “single-lens.” This means a camera that uses only one lens.

This one lens is used for taking and previewing the image. Back in the day, around the 1930s to the 1960s, cameras were using a twin-lens.

Twin lens camera.
Twin-lens camera

One lens was used for taking the photograph, while the other was used for the viewfinder system that allowed photographers to see their scene before taking a picture.

Single vs. twin lens camera.
Single vs. twin lens camera

Reflex

The third and final term is “reflex.”

This is what DSLR cameras are known for: their reflex design scheme. The design includes a mirror that reflects light from the lens into an optical viewfinder.

Graphic showing a DSLR reflex design scheme.
DSLR reflex design scheme

This allows us photographers to see exactly what the lens sees in real-time.

A viewfinder on a DSLR camera.
Can see through the viewfinder

So, we know that a DSLR camera is a type of digital camera known for its reflex design scheme.

But how does it actually work?


How does a DSLR camera work?

To understand how a DSLR camera works, I’ve found it’s easier to focus on three elements within the camera:

  • The light entering the lens
  • The mirror
  • The digital sensor

Looking through the DSLR camera

When you look through the viewfinder of a DSLR camera, you can see what the lens sees.

This happens because light enters through the lens of your camera, hits a mirror angled at 45 degrees, and then directs light up toward your viewfinder.

Moment of shooting

When you press the shutter button on your DSLR, the mirror flips out of the way, allowing the light to hit your digital sensor and capturing the image.

Fun fact: The mirror flipping up is also the reason why there is a brief blackout in your viewfinder when you are taking an image, and the reason there is that “click” sound.

Mirror down on digital camera light not hitting sensor.
Mirror is down - light not hitting sensor
Mirror up on digital camera light hitting the sensor.
Mirror is up - light hitting the sensor

Types of DSLR image sensors

DSLR cameras have different image sensor sizes, the two most common being full frame and APS-C (crop sensor).

A full frame sensor and a crop sensor camera.
Full frame sensor vs. APS-C (Crop sensor)

Full frame cameras

DSLRs with a frame the same size as 35mm film are called full frame cameras because they have full-frame sensors.

If you have a 50mm lens and you use it on a full-frame DSLR camera, then that 50mm lens will perform true to its focal length. For example, here's a photo I took using a 50mm lens on a full-frame sensor DSLR camera.

The focal length stayed true to 50mm, and in the next section, we will compare this with the same photo taken on the crop sensor.

Photo underneath the pier taken on a 50mm lens.
50mm Lens photo on full frame sensor

Here is what full-frame cameras are known for:

  • Full-frame cameras are often more expensive and also heavier than their counterparts
  • They often perform better in low-light conditions
  • They have a wider dynamic range
  • They provide a shallower depth of field at equivalent apertures
Graphic showing the benefits of full frame cameras.
Full frame benefits

APS-C (crop sensor) cameras

DSLRs with an APS-C (Advanced Photo System Type-C) sensor are also called crop sensor cameras. You guessed it. This is because they use a smaller image sensor than the full-frame sensor, hence the name “crop sensor.”

A graphic of a crop sensor camera.
Crop sensor DSLR camera

The size difference is typically 1.4-1.6 times smaller than a full-frame sensor.

Graphic showing a crop sensor is smaller.
Crop sensor is smaller

If you have a 50mm lens and you use it on a crop sensor DSLR camera, then there will be a 1.5x to 1.6x crop factor, and the focal length of that lens will behave like a 75mm-80mm (50mm x 1.5/1.6) lens.

For example, here's that same scene earlier that I took with the 50mm lens on a crop sensor camera, making it behave like a 75mm-80mm focal length (more zoomed in):

Photo underneath the pier on a 50mm lens on a crop sensor.
50mm Lens photo on crop sensor
Two photos taken on 50mm lenses on a full frame and a crop sensor.
Two photos underneath pier taken on 50mm

Here is what crop sensor cameras are known for:

  • Less expensive than their full-frame counterparts
  • More compact and lightweight
  • The ability to gather light is not as strong as full-frame cameras
  • The narrower field of view due to smaller sensor
Two bullet points comparing full frame and crop sensor cameras.
Full frame vs. crop sensor comparisons

Camera alternatives to DSLR cameras

We’ve talked a lot about DSLR cameras, which are solid “professional” cameras. What are the other options if you don’t want to use a DSLR camera?

At the beginning of this guide, I hinted that DSLR cameras are also less popular than they used to be. So why is that? Well, let’s look at some camera alternatives to DSLR cameras:

Mirrorless cameras vs. DSLR cameras

The introduction of mirrorless cameras is the main reason why DSLR cameras are less popular than they used to be.

You see, here is great debate among photographers about whether mirrorless cameras are essentially better versions of DSLR cameras and whether they should be the industry standard cameras.

Mirrorless cameras operate without a mirror, hence the name. So, instead of light entering the lens and reflecting on the mirror into the optical viewfinder, mirrorless cameras use an electronic viewfinder (EVF).

Graphic showing how a mirrorless camera works.
Mirrorless camera

When light hits the electronic viewfinder (EVF), a digital projection of the image is shown, and you can then see changes in exposure in real time before taking your photo!

This means if you make any changes to your exposureaperture, shutter speed, ISO – then it will be visible in your viewfinder. Pretty neat, huh? But with any advantages, there are also disadvantages. Let’s look at them now:

DSLR advantages vs. mirrorless cameras

  • Battery Life: DSLRs have better battery life because they take less power and are also smaller cameras in general, so they take batteries with lower charge capacities.
  • Cost: DSLRs range in price from entry-level to high-end, meaning that you can buy cheaper DSLRs. Mirrorless cameras are still relatively new, so there aren’t many cost-friendly entry-level mirrorless cameras…yet.
  • Choice of Selection: DSLR cameras offer a great choice of selection because they have been around for a long time.
  • Resources: You have more education resources and reviews on DSLR cameras because they have been around longer.

DSLR disadvantages vs. mirrorless cameras

  • Size: Mirrorless cameras are often lighter because they do not need to include the mirror and mirror-movement mechanism within the camera.
  • Speed: Mirrorless cameras are often faster due to the mirrorless aspect.
  • Autofocus: The autofocus is generally faster on mirrorless cameras since there is no mirror obstructing the sensor.
  • Sound: Mirrorless cameras don’t have that “click” sound because of the mirrorless aspect.
Graphic comparing a DSLR and mirrorless camera.
DSLR camera vs mirrorless camera comparisons

Point-and-shoot cameras vs. DSLR cameras

Point-and-shoot cameras are another camera alternative to DSLR cameras. These types of cameras are often very compact, small, and easy to use but have a fixed lens and automatic settings for focus and exposure.

DSLR advantages vs. point-and-shoot cameras

  • Manual Controls: Point-and-shoot cameras have limited manual controls
  • Bigger Sensors: Point-and-shoot cameras have smaller sensors, which can affect image quality and low-light performance

DSLR disadvantages vs. point-and-shoot cameras

  • Portable: Point-and-shoot cameras are more portable than DSLRs, with many being able to fit in your pocket.
  • Ease of use: Point-and-shoot cameras are easy to use, hence the “point-and-shoot” aspect.
  • Affordable: Point-and-shoot cameras are more affordable than most DSLR cameras and meant for more “casual” photographers who don’t prefer to change lenses.
Graphic comparing a DSLR and point-and-shoot camera.
DSLR camera vs point-and-shoot camera comparisons

Smartphone cameras vs. DSLR cameras

With the rise of smartphone capabilities, these devices that we carry 24/7 are now coming equipped with advanced cameras and computational photography features that can rival many traditional cameras.

But how do they fare against DSLR cameras?

DSLR advantages vs. smartphone cameras

  • More Control: DSLR cameras have more control over settings than smartphone cameras. While smartphones are adding more and more features, DSLRs still offer more manual settings since their main purpose is to capture images.
  • Bigger Sensor: DSLR cameras have bigger sensors, which provide stronger image quality and low-light capabilities. However, this gap is narrowing.
  • Optical Zoom: DSLR cameras have better optical zoom capabilities due to various lens choices.

DSLR disadvantages vs. smartphone cameras

  • Portable: Smartphone cameras are always with you, making them very portable.
  • Casual Photography: Smartphones are starting to fill that gap and becoming the preferred choice for casual photographers who just want to take photos of their family, scenes they see on vacation, or social media.
  • Advancing Rapidly: Smartphones are advancing at a rapid pace and keep adding new innovative features like portrait mode, night mode, and instant sharing capabilities.
Graphic comparing a DSLR and smartphone camera.
DSLR camera vs smartphone camera comparisons

After reading this guide, you may be persuaded to use a DSLR camera. So, what are the popular models and brands of DSLR cameras?

Canon DSLR cameras

I am a Canon user. I began my journey with their entry-level Rebel series, and I currently use a Canon 6D Mark II, which is known for being an amateur/professional-level camera.

Here are some of the leading DSLR cameras for the leading camera brand, Canon:

Nikon DSLR cameras

Nikon is another powerhouse within the photography industry. Here are some of the leading DSLR cameras for Nikon:

Pentax DSLR cameras

While not as popular as Canon or Nikon, Pentax still has a loyal following due to its durable cameras and in-body image stabilization. Here are some of the leading DSLR cameras for Pentax:


In summary, DSLR cameras are a tried and tested type of digital camera. While the rise of mirrorless cameras is raising questions about their “king” status as the industry standard, and smartphone cameras are bridging the gap between casual and amateur photographers, DSLRs are still a very popular choice.

Especially entry-level models. However, if my friends were just starting in photography and they asked me what type of camera to get, I’d recommend they get an entry-level DSLR camera like the Canon Rebel T7, and then if they wanted to upgrade, I’d probably tell them to look at the mirrorless camera options.

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