In this blog post, we’ll examine the structure and features of DSLR and mirrorless cameras, the differences in their image sensors, and the advantages these cameras offer compared to smartphone cameras.
As recently as the 1990s, before digital cameras became widely available, it was common to take photos using film. Not only did film require processes such as development and printing after shooting, but there were also limitations to sharing photos, making it difficult for as many people as today to enjoy photography as a daily hobby. Since then, with the widespread adoption of digital cameras and the inclusion of built-in cameras in smartphones, photography has become an activity that anyone can easily enjoy. Today, countless people take photos with their smartphone cameras and share them on social media. Nevertheless, while some people still carry around bulky DSLR cameras to take photos, the number of people using mirrorless cameras has also increased recently. Just by their names, it’s hard to tell what the difference is between DSLR and mirrorless cameras. Why do people carry these cameras around to take photos?
First, let’s find out what a DSLR camera is. DSLR is a term derived from “SLR” with the letter “D” (for “Digital”) added. SLR stands for Single Lens Reflex, which refers to a system that uses a mirror and a prism to direct light entering through a single lens to an optical viewfinder.
In the past, when film cameras were popular, this method allowed photographers to directly preview the light passing through the lens and projected onto the film before taking the shot. Therefore, compared to rangefinder (RF) cameras that use a separate viewfinder, the advantage was that photographers could accurately confirm the actual scene being captured. However, with the widespread adoption of digital cameras, it became possible to view the image captured by the image sensor directly on an electronic display, and this advantage has become relatively less important than in the past. On the contrary, the need for components such as a mirror and a prism in DSLR cameras has led to an increase in the camera’s size and weight, which has become a drawback.
Another characteristic of DSLR cameras is that most are designed to allow for interchangeable lenses. Although the mount—the part where the camera and lens connect—varies depending on the manufacturer and product line, the ability to swap out multiple lenses on a single camera is a highly appealing advantage. This is because a single camera allows you to use the lens that best suits the shooting situation, whether it’s a wide-angle lens or a telephoto lens.
Interchangeable-lens mirrorless cameras emerged as a response to these advantages and disadvantages of DSLR cameras. It is easy to understand that a mirrorless camera—which, as the name implies, “has no mirror”—is a camera that, unlike a DSLR, does not use a mirror or a prism structure for an optical viewfinder in the optical path. Since these components are not required, the camera can be made lighter and more compact, making it more portable than a DSLR. Furthermore, since they retain the key advantage of DSLRs—the ability to swap lenses—users can capture high-quality photos using a variety of lenses. Today, thanks to significant advancements in mirrorless camera image sensors, autofocus, and image processing technology, high-end models can deliver image quality that rivals that of DSLRs.
However, one of the key advantages that DSLRs and mirrorless cameras have over typical compact cameras or smartphone cameras is the size of their image sensors. An image sensor is a light-sensitive element in a digital camera that converts light passing through the lens into an electrical signal; you can think of it as performing a role similar to that of film in a film camera. Generally, a larger image sensor can capture more light under the same conditions, offering advantages in low-light photography and achieving background blur; when the lens and shooting conditions are the same, sensor size is also a key factor in determining image quality. This difference is particularly noticeable because many DSLRs and mirrorless cameras use larger image sensors than smartphone cameras.
However, image quality is not determined by sensor size alone; it is influenced by various factors, including lens performance, image processing technology, and shooting conditions.
In the past, DSLRs and mirrorless cameras were expensive and accessible only to a select few users, but as technology has advanced, products across a wide range of price points have been released, and interchangeable-lens cameras are now widely used not only by professional photographers but also by those who enjoy photography as a hobby. In particular, in the recent digital camera market, mirrorless cameras have established themselves as the core product line among interchangeable-lens cameras, and there is a clear trend toward developing new products and lenses centered on mirrorless cameras rather than DSLRs. According to 2025 global digital camera shipment statistics, shipments of interchangeable-lens cameras reached approximately 7 million units; while DSLR shipments declined to about 660,000 units, mirrorless cameras now account for the majority of the market. Therefore, when choosing a camera today, it is natural to consider mirrorless cameras alongside DSLRs. If you’re not satisfied with the image quality of your smartphone camera or want to experiment with photography using a variety of lenses, it might be worth considering a DSLR or mirrorless camera.
