A mirrorless camera is a type of digital camera that, unlike a traditional digital single lens reflex camera, does not incorporate a reflex mirror system between the lens and the image sensor. In a conventional DSLR, a mirror positioned at a 45 degree angle behind the lens reflects light upward through a pentaprism or pentamirror into an optical viewfinder, allowing the photographer to see directly through the lens. When the shutter is released, the mirror flips up out of the light path, allowing light to reach the sensor for the duration of the exposure before returning to its viewing position. In a mirrorless camera, this entire mirror and optical viewfinder assembly is absent - light passes directly and continuously through the lens to the image sensor, which reads the incoming image data in real time and feeds it to an electronic viewfinder or rear LCD screen for composition and preview.
The elimination of the reflex mirror assembly has profound consequences for the design, size, and capabilities of the camera system. Without the mirror box that a DSLR requires between the lens mount and the sensor, the flange distance - the distance between the lens mount and the focal plane - can be made considerably shorter, allowing the camera body to be designed in a significantly more compact and lightweight form factor while still accommodating a full size image sensor. This shorter flange distance also has important optical implications, as it enables the design of wide angle and standard lenses with optical constructions that take advantage of the shorter back focus distance, potentially achieving superior optical performance compared to equivalent DSLR lenses constrained by the longer flange distance required to clear the mirror box.
The electronic viewfinder that replaces the optical viewfinder of a DSLR displays a real time live view feed from the image sensor, showing the scene as the sensor actually captures it with any exposure, white balance, colour profile, and creative filter settings applied and visible in the viewfinder before the shot is taken. This what you see is what you get preview capability is a significant practical advantage over the optical viewfinder of a DSLR, which shows the scene in its natural appearance regardless of the camera settings applied, as it allows the photographer to assess and adjust the final appearance of the image before making the exposure. Electronic viewfinders have advanced enormously in resolution, refresh rate, and dynamic range over successive generations of mirrorless camera development, with the finest current EVFs offering a viewing experience that rivals or surpasses the optical viewfinder in many practical respects.
Mirrorless cameras have developed autofocus systems of exceptional sophistication and performance, in part because the absence of a mirror allows the autofocus system to use the image sensor itself as the primary focus detection device through a technology known as on sensor phase detection autofocus. By embedding phase detection pixels directly into the image sensor alongside the standard imaging pixels, mirrorless cameras can perform phase detection autofocus across a very wide area of the frame - in some cases covering virtually the entire image area - with the speed and precision of phase detection rather than the slower contrast detection method that earlier live view and mirrorless systems relied upon. The most advanced mirrorless autofocus systems incorporate artificial intelligence based subject recognition algorithms capable of detecting, identifying, and tracking human faces and eyes, animal faces and eyes, birds, vehicles, and other specific subject categories with remarkable accuracy and reliability, maintaining focus on moving subjects across the full frame at continuous shooting speeds that would have been impossible with earlier autofocus technologies.
The absence of the mirror and its associated mechanical components also brings several additional practical benefits. Without the mirror slap - the vibration caused by the mirror flipping up at the moment of exposure - mirrorless cameras can achieve completely silent electronic shutters that produce no vibration whatsoever, making them ideal for shooting in quiet environments such as concert halls, courtrooms, and wildlife hides where mechanical shutter noise would be intrusive or disturbing. The continuous live view feed from the sensor also enables more accurate and consistent exposure metering and white balance assessment than the separate metering sensors used in DSLR optical viewfinder systems, and facilitates seamless video recording without the disruption of mirror lockup that affects video shooting on DSLR cameras.
Modern mirrorless cameras from all major manufacturers now offer comprehensive feature sets that match or exceed those of professional DSLR systems, including high resolution full frame and medium format sensors, in body image stabilisation systems that compensate for camera shake across multiple axes, 4K and higher resolution video recording with professional grade codec options, and continuous shooting speeds of ten, twenty, or even more frames per second with full autofocus and autoexposure tracking between frames. The major camera manufacturers including Sony, Canon, Nikon, Fujifilm, and Panasonic have invested heavily in developing extensive mirrorless lens systems to complement their camera bodies, and the breadth and optical quality of available mirrorless lenses now rivals the established DSLR lens ecosystems that took decades to develop.
The shift of the photography industry towards mirrorless technology has been one of the most significant developments in camera design since the transition from film to digital, reflecting both the genuine performance advantages that the mirrorless architecture offers and the changing needs and priorities of photographers who value compactness, electronic viewfinder preview, and the advanced autofocus capabilities that the sensor based approach enables. While DSLR cameras continue to be used by many photographers who have invested in existing lens systems and value the optical viewfinder experience, the direction of new product development across the industry strongly favours mirrorless systems, and mirrorless cameras have become the primary tool of choice for the majority of professional photographers and serious enthusiasts entering the market today.