The Mirrorless Camera
The mirrorless camera is a pure digital-era derivative of the D-SLR, maintaining the versatility and flexibility of interchangeable lenses. However, the adoption of an electronic viewfinder (EVF) enables the elimination of the reflex mirror and, obviously, the pentaprism-based optical viewfinder. This not only allows for a more compact and lighterweight camera body, but also potentially faster shooting speeds and near-silent operation.
Another benefit of eliminating the reflex mirror is a lens mount with a shorter flange back distance which gives more scope for designing wider-angle lenses. With the need to adopt a new mount, a number of camera makers have also taken the opportunity to give it a wider throat diameter which, in turn, allows for the development of lenses with faster maximum apertures.
Initially the emphasis with mirrorless cameras was on making them as small as possible and a number of systems adopted smaller sensor sizes to help achieve this. Over time there’s been a return to the larger sensor formats commonly used in D-SLRs and while mirrorless cameras are still more compact than a comparable reflex body, the other benefits of the design are now being exploited (such as faster continuous shooting speeds). Mirrorless cameras are also called compact system cameras (CSCs), but the generic “mirrorless” is becoming more widely used given the lessening emphasis on body size alone. Mirrorless cameras are now available with Micro Four Thirds, ‘APS-C’, full-35mm and medium format size sensors. There are basically two body styles which are often referred to – a little confusingly – as either “SLRstyle” or “rangefinder-style” due their shapes which, in turn, are largely dictated by the location of the electronic viewfinder.
▲ This cutaway shows how eliminating the reflex mirror and optical viewfinder allows for a more compact camera body.