Mirrorless cameras are a bit of a buzzword at the moment. At one time, any serious photographer or hobbyist would get a DSLR – but now mirrorless cameras increasingly offer the same image quality, versatility and features in a smaller, lighter body.
The difference between mirrorless cameras (also called ‘compact system cameras – CSCs’) and DSLRs really is as simple as the term suggests. Where DSLRs use a mirror in the body to reflect the image seen through the lens up into an optical viewfinder, mirrorless cameras have no mirror. Instead, the image from the lens goes straight through to the back of the camera and the main sensor. The sensor then feeds and electronic image to the rear screen or, if the camera has one, to an electronic viewfinder (EVF).
To be fair, compact cameras are also, strictly, speaking, mirrorless since they too use the main sensor to create the image used to compose the photo. However, the term ‘mirrorless camera’ is taken to mean mirrorless interchangeable lens cameras (ILCs) to distinguish them from DSLRs.
Mirrorless camera pros and cons
It’s true that mirrorless camera bodies are almost always smaller than DSLR bodies, though that doesn’t quite tell the whole story. Where cameras use the same sensor size, you will typically find that the lenses are the same size too. A mirrorless camera’s body may be smaller than a DSLRs but use lenses that are just as big, eroding any size advantage. A small mirrorless body with a regular size lens can also feel a little front-heavy and unbalanced.
DSLRs use separate phase detection autofocus modules for viewfinder shooting, whereas mirrorless cameras have to use the main sensor for autofocus, either using slower contrast autofocus systems or newer on-sensor phase detection or hybrid autofocus systems. These are now largely as effective as DSLR autofocus sensors, even for high-speed subject tracking.
The tables are turned when you want to use the camera’s rear screen for composing your shots in ‘live view’ – and this is essential when shooting video. With the DSLR design it means the mirror must be locked up, which disables the regular autofocus sensor. The camera now has to use its on-sensor autofocus, and traditionally this has been based around slow contrast autofocus. Canon has an on-sensor Dual Pixel CMOS AF system, however, that makes its latest DSLRs just as effective for live view photography and video as a mirrorless camera.
One significant drawback of mirrorless cameras is their heavier battery consumption (due to their constant electronic live view display). A mid-range DSLR might have a battery life of 1,000 shots between charges, but a comparable mirrorless camera might only capture 300 shots on a charge.
Nevertheless, mirrorless cameras are steadily taking over the photography market – especially for video – as manufacturers invest more heavily in this technology than DSLRs.
The lack of a mirror in the body means that the flange distance – the distance between the lens mount and the sensor – is shorter. This means camera makers have had to make new lens ranges for these cameras, but the removal of the distance limitation has led to new, more modern and more innovative lens designs. What’s more, because the lens to sensor distance is shorter, it leaves space for lens adaptors which allow the use of of many types and brands of DSLR lens on mirrorless camera bodies. This mixing and matching of lenses via adaptors is very popular amongst videographers.