What Is DSLR Camera & How Does It Work?

Jeff Picoult

By Jeff Picoult

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Photographers have varying preferences and shooting needs, which explains the various types of cameras available on the market. A DSLR camera is the best bet for those seeking an optical viewfinder or interchangeable lenses for more control over depth of field!

DSLR Camera

Given that many newcomers still feel unsure about their capabilities, our article will discuss the DSLR camera definition in further detail. 

What Is A DSLR Camera?

DSLR stands for Digital Single Lens Reflex. Though single-lens reflex  (SLR) cameras have existed since the nineteenth century, the first commercial DSLR with image sensor attachment only appeared in the late 1990s.

Modern DSLR camera

This digital single-lens reflex camera uses the mirror surface to bounce light to the optical viewfinder through its lens. When you press the shutter button, the mirror swings up so the light can hit the digital sensor and capture the picture immediately.

Unlike traditional point-and-shoot or phone cameras, DSLRs have the advantage of interchangeable lenses. You can have a wide-angle lens for landscapes, a telephoto lens when zooming in on distant subjects, or a macro lens to capture close-up details! The wide range of options will cater to all different photographic needs. 

How A DSLR Camera Works

A glance through the DSLR viewfinder shows you exactly what the lens connected to your camera sees, giving you a clear preview of your shot. Here’s how it works: 

How A DSLR Camera Works
  • The light of a particular sense you want to capture will pass through the camera’s lens into a mirror inside the chamber. That reflex mirror sits at a 45° angle and vertically directs the light to a pentaprism. Next, the pentaprism redirects the light horizontally through two different mirrors into the optical viewfinder. 
  • When you snap a photo, the mirror swings upwards to block the vertical path. The shutter opens, and the light hits the sensor directly, recording the image. 
  • Afterward, the shutter closes, and your reflex mirror drops back onto its 45° position to redirect light to the viewfinder.

But things do not end there. The cam’s processor takes the data from the digital image sensor, processes it, and writes everything to the memory card. The entire procedure wraps up quickly; some professional DSLR cameras can even repeat it 11 times in less than a second!

Key Features Of A DSLR Camera

Shooting Modes

Aperture Priority Mode

Aperture Priority Mode

In this mode, you adjust and control the aperture so your camera can determine the shutter speed depending on other settings (aperture included).

Adjusting this aperture affects the sharpness of background elements. For example, wider apertures blur the background to focus better on the main subject, but narrower ones include more detail in the scene. It also regulates the amount of light reaching the sensor (wider apertures let in more light, narrower ones less).

Shutter Priority Mode

Shutter Priority Mode

Contrary to Aperture Priority Mode, you manage the shutter speed this time while your camera takes over the aperture. You can tweak the speed to freeze motion (faster speeds) or blur motion (slower speeds).

Like aperture adjustment, light intake is also altered during this process. Faster speeds let in less light (since the shutter closes faster), while slower speeds let in more.

Manual Mode

This mode grants you control over both aperture and shutter speed, allowing for complete customization of settings for more artistic control over your digital photography journey.


ISO in Camera

ISO determines the light sensitivity of your interchangeable-lens camera: 

  • Lower ISO numbers (e.g., 100 to 400) mean less sensitivity, resulting in dark photos unless compensated with additional light sources.
  • Higher ISO numbers (e.g., 800 to beyond 2000) increase sensitivity for brighter images. However, they might sacrifice image quality, especially above ISO 1600. 

Long story short, lower native ISO settings are better if you seek to produce higher-quality images. 

Nevertheless, higher ISO settings can be quite useful in low-light conditions or during continuous shootings for special events that might never occur a second time. Nobody complained about the lack of HD videos or images of the world’s first moon landing, after all! 

Focusing Modes

This setting determines how your autofocus system operates. There are two options: spectrum and single-point focus. 

Compared to the spectrum, single-point provides more reliable and less distracting focusing. It also allows you to select a specific focus point (usually at the frame’s center, though you can always adjust it to the desired subject).

Back Focusing

With back focusing, your camera assigns the autofocus feature to another button other than the shutter button to avoid accidental changes in focus settings. This advantage helps enhance workflow and reduces the risk of missing crucial shots, particularly in critical situations like light painting shoots.

Exposure Compensation

Exposure compensation adjusts the brightness of images beyond what aperture, shutter speed, or even ISO settings alone can achieve. A great choice if you want to fine-tune exposure in less-than-ideal lighting conditions!

  • Decreasing exposure compensation in dark settings prevents the over-brightening of light sources.
  • Conversely, increased exposure maintains accurate color intensity in bright sunlight or settings, especially for whites (e.g., snow).

Pros and Cons of A DSLR Camera

The Pros

  • Its optical viewfinder is a huge improvement over the electronic viewfinder. It provides a real-time, uninterrupted view of the scene through the lens, ideal for fast-action photography and bright outdoor conditions. The risk of battery drains is also unlikely.
  • DSLRs typically have larger image sensors than point-and-shoot cameras, which boosts image quality: superior low-light performance, sharper images, and more control over background blur.
  • As said earlier, interchangeable lenses remain its biggest strength. For instance, you can switch from a wide-angle to a macro lens for intense close-up shots or use a telephoto lens for distant shooting. The choice is entirely up to you.
  • DSLRs offer extensive manual controls for shutter speed, aperture, ISO, white balance, and more, giving you ample customization and creative control over your final images.

The Cons

  • Unfortunately, DSLRs with attached lenses can be significantly bulkier and heavier than other more compact cameras (like mirrorless-system cameras or point-and-shoots). This huge drawback is quite hard to ignore, especially if you constantly travel or prioritize portability.
  • While some appreciate the variety of manual controls, beginners usually find them overwhelming. Mastering all the settings (exposure, aperture, shutter speed, and others) takes time and practice.
  • High-end models with professional-grade lenses are much more expensive than standard cameras, so assess your budget carefully if you are not yet an experienced photographer.
  • When you take a picture with a DSLR, the mirror flips up momentarily to allow light to reach the sensor. It creates a brief blackout in the viewfinder, so you might sometimes struggle to see the scene clearly when capturing the image.

Is It Worth It?

Yes. DSLRs excel in dim lighting and offer incredible versatility with their interchangeable lenses and extensive manual controls.

However, their bulky size and complex settings (not to mention the high entry costs) make them seem less beginner-friendly. Consider a basic, less expensive camera, such as one with no mirror mechanism, if you want a safer starting point!

See more: 22 Main Parts Of A Camera And How They Work


Like any type of camera, DSLR cameras have their downsides. But the excellent image quality easily makes up for that, especially for professional photographers!

Don’t hesitate to ask us for advice if you still feel overwhelmed by this art form. Start with a simpler, cheaper digital camera (like a mirrorless camera) first until you’re ready to take things to the next level.

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Jeff Picoult

Jeff Picoult


Jeff Picoult is a seasoned photographer, who blends artistry and innovation. With a humble approach, he captures moments resonating with depth and emotion, from nature's beauty to the energy of sports.

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