WHILE by no means a flop, the most innovative idea to come out of the Japanese camera industry in decades—the mirrorless digital camera—has not exactly taken the photographic world by storm. By dispensing with the mirror in front of the shutter of a digital single-lens reflex (DSLR) camera—which redirects the image seen by the lens to an optical viewfinder above, before flipping briefly out of the way for a picture to be taken—the mirrorless camera promised to be lighter, smaller and quieter, with a specification only marginally less than its bulkier big brother at the pricier end of the market.
Introduced by Epson in 2004, but popularised largely by Panasonic and Olympus from 2008 with their jointly developed “Micro Four Thirds” format, the mirrorless camera was heralded as the saviour of the industry’s struggling second-tier of photographic firms—ie, all those below Canon and Nikon, the world leaders in photography. Sitting between compact cameras at the low end of the market and entry-level DSLRs at the high end, the mirrorless format encompassed benefits of both, with few of either’s drawbacks.
Unfortunately, happy snappers found other ways of taking pictures. Indeed, the compact-camera business has been in free-fall since people started using smartphones to take pictures instead. Compact-camera sales dropped more than 40% last year, according to IDC, a market-research firm.
Whereas popular photography was once all about making prints to stick into the family album, its main purpose now is for uploading images to Instagram, Flickr, Twitter or Facebook. The ability to transmit pictures instantly to social networks with the swipe of a finger has immense appeal. Smartphones do this better than even the fanciest of digital cameras. And while camera-makers have rushed to add Wi-Fi to their latest models, the implementations leave much to be desired. Gadget users today value instant connectivity above everything; certainly, far more than picture quality, given the mostly poor graphical resolution of the web.
Snapped in the middle
That has left mirrorless cameras squeezed between increasingly sophisticated smartphones that cost much less, and entry-level DSLRs that cost not all that much more. Lacking robust sales, the worry is that mirrorless cameras could be starved of research and development funds. If that happens, the innovation they have brought to photography could falter.
That would be a pity. Mirrorless cameras embody a level of technical creativity the camera industry has not seen in ages. Take the DSLR, used by most professional photographers. It crams a number of decade-old developments between the lens and the image sensor. Among other things, there is an image stabiliser, to correct for handshake; a low-pass filter, to eliminate interference caused by repetitive patterns in fabrics and the like; and a mechanism to clean the sensor of dust after a lens has been changed.
Lodged in there as well is a sophisticated phase-detection system for focusing the lens automatically. This uses a secondary mirror (attached to the main one) along with a dedicated sensor to measure the convergence of two light beams. Then there is a motor to snap the lens into focus. This makes the DSLR an expensive piece of machinery that requires precision assembly and skilled craftsmen for installation and calibration.
For these extra components to be accommodated, along with the mirror box for the optical viewfinder and the auto-focusing mechanism, the “flange-back” distance—from the back of the lens to the sensor’s imaging plane—needs to be fairly long. That is why DSLRs are bulkier than the old analogue models that exposed the image from the lens onto rolls of film. It also means they can never be as slim as compact cameras, which use simpler but less accurate viewfinders.
However, dispensing with the DSLR’s mirror assembly eliminates not only the optical viewfinder and its chunky pentaprism, but also the expensive auto-focusing mechanism. The flange-back distance can then be reduced significantly. The camera body becomes more compact, lighter and cheaper to build, as do the interchangeable lenses it uses.
With the optical viewfinder gone, mirrorless cameras have to rely on either an LCD display on the back of the camera for taking pictures, as a smartphone does, or an electronic viewfinder for eye-level shooting. Electronic viewfinders use a small LCD inside the camera to display the image falling on the sensor. Being electronic, they can overlay all sorts of additional information on the viewfinder screen for the photographer to see at a glance. Optical viewfinders offer little more than the basics—ie, film speed, shutter speed, aperture and possibly battery life.
To keep costs down, mirrorless cameras initially adopted a much cheaper contrast-detection method for automatic focusing, as found in compact cameras. Relying on the main sensor to do all the calculations, this needs no costly additional components. But the focusing process—involving repeatedly testing a small part of the image to calculate its sharpness—requires a lot of computation. As a result, focusing can be too slow for sports events, bird-watching or other forms of action photography. To overcome this, recent mirrorless cameras use a separate sensor to perform both contrast- and phase-detection calculations, and can focus as fast as all but the best DSLRs. Mirrorless cameras with this hybrid auto-focusing are now the norm.
As for sensor size, mirrorless cameras started off using mostly the Micro Four Thirds format, with an area 30% less than the standard APS-C sensor used in DSLR cameras, but nine times greater than those in compact cameras and smartphones. While Panasonic and Olympus have stuck with Micro Four Thirds, most of the other mirrorless makers have now migrated to the bigger APS-C. Sony and Leica now sell mirrorless cameras with a full-frame sensor (ie, the size of old 35mm film). Canon and Nikon have put a toe into the mirrorless market with some products. But unless they embrace the technology wholeheartedly, the big innovation in photography is likely to remain stuck in a niche.