Lighten Up! Go Mirrorless!

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Today, you can choose from a wide line of cameras that are truly compact, produce DSLR image quality and accept interchangeable lenses: the mirrorless cameras. Introduced just four years ago, the mirrorless cameras (with few exceptions) feature DSLR sensors in very compact bodies. Sigma was the first to put a DSLR sensor into a truly compact body with its DP1 in 2008. That camera, like its successors, has a built-in fixed-focal-length lens. Later in 2008, Panasonic introduced the Lumix DMC-G1, the first of the mirrorless interchangeable-lens cameras. Today, seven manufacturers produce such cameras, and they're the fastest-growing camera market segment—for good reason. Many photographers are finding these systems ideal for travel and shooting high-quality video footage, as well as general nature photography, because they let you lighten the load without compromising your image-making options. These aren't just small camera bodies; they're sophisticated, full-featured systems, and if you haven't considered one, you should.

Panasonic Lumix DMC-GH2

Mirrorless cameras come in two basic styles—those that look like mini-DSLRs, and those that look like flat compact digital cameras. DSLR users will feel more at home with the former, while compact camera users may be more comfortable with the latter.

Pros And Cons
The obvious benefits of mirrorless interchangeable-lens cameras are truly compact size coupled with DSLR image quality and the ability to take a variety of lenses. At a glance, a mirrorless body with a lens might be confused with a "point-and-shoot," all-in-one-style camera, but don't be fooled. Mirrorless interchangeable-lens systems are compact, but their large image sensors deliver much better image quality, and you can choose among a variety of lenses and other accessories.

We can't stress enough the advantages of compact size and weight to the outdoor photographer traveling or in the field. Anyone who has carted a big DSLR system onto an airliner or taken one afield understands this. A mirrorless system is a fraction of the size of an equivalent DSLR system. Generally, mirrorless bodies are point-and-shoot camera size. The Micro Four Thirds and smaller mirrorless systems also have much smaller lenses than comparable DSLR lenses. To cover the APS-C image format, APS-C mirrorless systems have larger lenses than the Micro Four Thirds systems, but they're still smaller than equivalent DSLR lenses—and, again, the camera bodies are much smaller.

Sony's NEX-7 features a 24.3-megapixel APS-C sensor and a built-in OLED electronic viewfinder along with a large LCD monitor. It's an example of the "flat" mirrorless-camera form factor.

The compact mirrorless bodies are made possible mainly by doing away with the bulk, complexity and cost of the DSLR's mirror box, moving mirror, focusing screen and pentaprism/pentamirror eye-level optical SLR viewfinder. Thus, the mirrorless models lack the DSLR's eye-level optical viewfinder. So you have to compose and (when desired) focus manually using the LCD monitor on the back of the camera (not a problem for those moving up from a compact digital camera, but a learning experience for the DSLR user). LCD monitors are hard to see in bright light and require the camera to be held away from you, which isn't the most steady way to handhold a camera, especially with longer focal lengths. Some mirrorless cameras have built-in electronic viewfinders, and with some others, an EVF is available as an optional accessory, which provides eye-level viewing more familiar to the DSLR user. EVFs aren't as good as SLR optical finders in dim light and for action shooting, but can display a lot of camera data and are convenient for eye-level viewing when shooting video. Some feel that the best of the current EVFs (such as Sony OLED EVFs) are better than the pentamirror optical finders built into entry-level DSLRs. Keep in mind that to use either the EVF or the external monitor, the camera must be switched on and "awake," while a DSLR's optical finder is always "on."

This brings us to the major drawback of mirrorless cameras for nature photography: battery life. Because they're always in Live View mode, they use up the battery more quickly than a DSLR. And to keep size down, most mirrorless cameras use smaller batteries than DSLRs, further reducing the number of shots you get per battery charge. Compact camera users moving up to a mirrorless model actually may be pleasantly surprised; most mirrorless models get more shots per charge than most compact all-in-one cameras. But DSLR users will have to get used to a lot fewer shots per charge than they have come to expect. With any camera, it's a good idea to carry a spare charged battery or two; it's especially important with mirrorless cameras.

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Olympus OM-D E-M5

Autofocusing
By and large, mirrorless cameras use contrast-based autofocusing right off the image sensor, as opposed to phase-detection AF used by DSLRs. Contrast-based AF used to be much slower than phase-detection AF (and it still is in most DSLRs' Live View mode). But contrast-detection AF has improved considerably over the years and now rivals phase-detection in speed, although it still isn't as good as phase-detection for action subjects such as birds in flight with long lenses. On the other hand, a number of mirrorless cameras provide touch-screen AF—just touch the spot in the image on the LCD monitor where you want the camera to focus, and the camera will focus there.

There are a few interesting phase-detect exceptions. To give photographers a phase-detect option, Sony created the unique LA-EA2 Alpha NEX Camera Mount Adapter. It lets you use Sony DSLR lenses (and legacy Konica Minolta Maxxum lenses) on NEX cameras for quick, DSLR-style phase-detection AF (see the sidebar on page 71). Also, Nikon's J1 and V1 feature a hybrid AF system that uses phase-detection AF in good light and contrast-detection AF when the light is too dim for phase-detection. When the light level is bright enough, the phase-detection provides good performance on moving subjects.

Sensor Sizes
Mirrorless cameras are available with sensors ranging in size from compact camera size to APS-C size. All other things being equal, larger sensors mean better image quality because they collect more light due to their larger surface areas. More light means less noise and a higher signal-to-noise ratio. The best mirrorless cameras equal the best non-full-frame DSLRs in image quality. The smaller-sensor mirrorless cameras are physically smaller in size than the larger-sensor models, but pay a price in image quality for that size advantage.

Besides image quality, the sensor size affects the angle of view of any lens. Compared to a full-frame sensor (36x24mm), an APS-C sensor has a focal-length crop factor of 1.5x so a 100mm lens on an APS-C camera frames like a 150mm lens on a full-frame camera, and a Micro Four Thirds sensor has a 2x crop factor, meaning a 100mm lens on a Micro Four Thirds camera frames like a 200mm lens on a full-frame DSLR. The CX sensor in Nikon's J1 and V1 cameras has a 2.7x focal-length factor (a 10mm lens frames like a 27mm lens on a full-frame DSLR), and the 1/2.3-inch sensor in the Pentax Q has a 5.5x factor (an 18mm lens frames like a 100mm lens on a full-frame DSLR). Mirrorless interchangeable-lens cameras that use APS-C sensors include all Samsung and Sony models, the Pentax K-01 and the Fujifilm X-Pro1. All Olympus and Panasonic mirrorless models use Micro Four Thirds sensors.

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The Pentax K-01 features an APS-C sensor and a stylish design.

Lenses
Each manufacturer of mirrorless cameras offers a line of lenses for those cameras. These lines are somewhat limited compared to the lens lines offered for the same manufacturer's DSLRs (except the Pentax K-01, which uses the same lenses as Pentax DSLRs). Most manufacturers offer at least one flat "pancake" lens, which makes the camera pocketable as long as it's a big pocket. The bottom line is that the smaller the sensor, the smaller the system. But even the largest mirrorless systems are considerably smaller and lighter than the smallest DSLR systems. Note that all Micro Four Thirds System cameras (Olympus and Panasonic, currently) can use all Micro Four Thirds lenses regardless of manufacturer. See the accompanying chart for a list of what's available.

To supplement their mirrorless lens lines, some manufacturers offer adapters that let you use their DSLR lenses on their mirrorless bodies. Because mirrorless cameras have such short flange-back distances (the distance from the lens mount to the image sensor), you can use any lens for which an adapter can be found. If the camera's flange-back distance is too great for the lens, the lens won't focus out to infinity. If the camera's flange-back distance is too short for the lens, the lens will focus beyond infinity, which isn't as big a problem. Most adapters are of the proper thickness to produce the right flange-back distance for the lens when mounted on the camera for which the adapter was designed.

Olympus and Panasonic offer adapters that let you mount standard Four Thirds System lenses on Micro Four Thirds mirrorless cameras, in most cases retaining all camera features. Panasonic offers adapters to mount Leica M and R lenses on Micro Four Thirds cameras; Olympus has an adapter that lets you use Olympus OM film SLR lenses on the cameras.

Adapters Expand Lens Options
Sony offers two adapters that let you use Sony (and legacy Konica Minolta Maxxum) SLR lenses on the NEX mirrorless cameras. Nikon's FT1 Mount Adapter lets you use Nikon DSLR lenses on the J1 and V1, providing single-shot autofocusing with Nikon AF-S lenses. Samsung makes a Pentax adapter that lets you use Pentax SLR lenses with the Samsung NX camera. As yet, Pentax does not provide adapters for the Q cameras.

Independent companies such as Novoflex and Pro-Optic offer adapters to attach a wide range of lenses to mirrorless cameras. While the adapters provided by the mirrorless camera makers generally support all camera features, the third-party adapters usually just let you attach the lens; there's no autofocusing, and exposure is either manual or aperture-priority. Some of the lenses that you can adapt to mirrorless bodies include the Canon FD and EF, Contax/Yashica, Leica M and Leica R, M.42, Minolta Maxxum/Sony A, Minolta MD, Nikon, Olympus OM, Pentax K, Tamron T2 and even Pentax 67, Mamiya 645 and Hasselblad medium-format lenses. The Pro-Optic NKM43A attaches Nikon lenses and provides tilt capability. Redrock Micro's LiveLens Micro Four Thirds adapter lets you mount Canon EF lenses on Micro Four Thirds cameras.

Accessories
While mirrorless camera systems currently aren't as comprehensive as DSLR systems, they still offer a number of useful accessories besides lenses and lens adapters. Note that not all mirrorless accessories are compatible will all camera models in a manufacturer's mirrorless line; check compatibility before purchasing a specific unit for a specific camera.

For the J1 and V1, Nikon offers a wireless remote control, a geotagging GPS unit, a stereo microphone and the SB-N5 flash unit (V1 only).

Accessories for Olympus mirrorless cameras include the MAL-1 Close-up Spotlight/Macro Arm Light, PEN PAL Bluetooth Communication Unit PP1, Electronic Viewfinders VF-2 (1.0x magnification) and VF-3 (1.5x magnification, 100% field of view), External Microphone Adapter Set and two electronic flash units—all of which connect via the accessory port atop the camera (and thus can be used only with models that have this port). There are also filters, cases, grips for the E-P3, underwater housings for the E-PL1 and E-PL2, and fisheye, wide-angle and macro converters.

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Panasonic accessories include three flash units, a remote shutter, an AC adapter, filters, cases, bags, straps and SD cards. Video accessories include the DMW-MS1 Stereo Microphone and DMW-ZL1 Zoom Lever. There are also wide, tele, macro and fisheye converters.

Pentax offers the optional accessory Viewfinder O-VF1 for the Q, which provides eye-level viewing (it's a glass optical device, not electronic). For the K-01, there are three flash units (including a macro ringlight), off-camera flash adapters, a remote control and a GPS unit.

Samsung offers a GPS unit and two flash units for its NX mirrorless cameras.

Sony mirrorless accessories include a compact stereo microphone, an optical eye-level viewfinder, a portable monitor, remote controller, tripod, an external flash unit and an OLED eye-level electronic viewfinder (NEX-5N and NEX-F3).