A DSLR or digital single-lens reflex camera is an advanced type of digital camera that offers excellent image quality, high-performance levels and premium-level manual control options, usually much better than what you would have with a camera with a fixed lens on a smartphone. This type of camera uses interchangeable lenses, while a camera with a fixed lens has a lens built into the camera body and the photographer cannot replace it.
Although photographers of almost all levels of experience can buy and use a DSLR camera, these types of cameras are the best for photographers who have experience with digital photography. Since DSLR cameras can cost from several hundred to several thousand euros, they are generally more suitable for photographers who have enough experience to take advantage of their high-end features.
DSLR vs. Mirrorless Cameras
However, DSLR cameras are not the only type of interchangeable lens camera. Another type of interchangeable lens camera, called a mirrorless camera, has a different interior design than a DSLR.
The interior design of the DSLR camera contains a mirror that prevents light from moving through the lens and hitting the image sensor. (The image sensor is the light-sensitive chip inside the digital camera that measures light in the scene, which is the basis for creating a digital photo.)
When you press the shutter button on the DSLR, the mirror rises from its position, allowing light traveling through the lens to reach the image sensor.
A mirrorless interchangeable lens (ILC) camera does not have the mirror mechanism on the DSLR. Light continuously hits the image sensor.
Optical viewfinder design
This mirror design has remained from the time of SLR film cameras, where every time the film was struck by light, it was exposed. The mirror mechanism has ensured that this only happens when the photographer has pressed the shutter button.
However, with digital cameras that use image sensors, the mirror is not really necessary for this purpose.
The mirror allows the DSLR to use an optical viewfinder since the mirror redirects the light entering the lens upward and into the viewfinder mechanism, which means you can see the actual light from the scene traveling through the lens. This is why you will sometimes hear an optical viewfinder of a DSLR called a viewfinder through the lens (TTL).
A mirrorless camera does not use an optical viewfinder because it does not have a mirror mechanism. Instead, if the mirrorless camera includes a viewfinder, it's an electric viewfinder (EVF), which means it's a small display screen, which shows the same image that appears on the screen on the back of the camera.
These small screens in the viewfinder all have different resolution levels (i.e. the number of pixels they use in the display), so some photographers don't like some digital viewfinders because they may not have a high resolution.
DSLR style cameras
A digital camera model that looks like a DSLR, but does not offer a TTL viewfinder or interchangeable lenses, is often called a DSLR-style camera. It is a camera with a fixed lens, but it has a large lens barrel and a large camera body that makes it look like a DSLR, both in body design and in the size and weight of the camera.
Such DSLR-style fixed-lens cameras tend to have a large telephoto capability, allowing them to take long-distance photos, such as the Nikon Coolpix P900 and its 83X optical zoom lens.
Although these large zoom cameras look like DSLRs, they don't have the high-end image quality or fast performance levels that even the simplest DSLR has.