Leica still makes 35mm rangefinder cameras (M7 with aperture-priority AE and fully mechanical MP, which can operate without a battery). But they also make full-frame M-series digital cameras, currently the M Typ 240 (with a 24-megapixel CMOS sensor), M-E (with an 18-megapixel CCD sensor) and M Monochrom (with an 18-megapixel monochrome CCD). All are quite compact compared to even entry-level full-frame DSLRs: The digital M cameras measure 5.5×3.1×1.7 inches (about 29 cubic inches), while the smallest full-frame DSLR measures 5.6×4.3×2.6 inches (about 62.5 cubic inches).
All Leica M bodies are designed specifically to work with the legendary Leica M-series rangefinder lenses (as are the sensors in the digital models), which currently number 22, from 16mm through 135mm. Add the optional Leica R-Adapter M, and you can use Leica R-series SLR lenses. The R-lenses are no longer in production, but are available on the used market; they extend the focal-length range from 15mm to 400mm. It’s best to use the optional Visoflex EVF2 electronic viewfinder with the R lenses, as the camera’s rangefinder was designed for focal lengths from 16-135mm. Of course, with the M Typ 240, you can also use the LCD monitor in live view mode.
Sony‘s a7 series mirrorless full-frame cameras are almost as small as the Leica Ms: 5.0×3.7×1.9 inches (about 35 cubic inches), with weights from 14.3 to 15.7 ounces. They come in three flavors. The a7, with a 24.3-megapixel Sony Exmor CMOS sensor, is the lowest-priced full-frame digital camera ($1,499). The a7R ($2,299), with a 36.4-megapixel Sony Exmor CMOS sensor and no AA filter, is geared for ultimate resolution. The newest a7 camera is the a7S ($2,499), which was unveiled just before the NAB show in April. It features a 12.2-megapixel Sony Exmor CMOS sensor, and it’s particularly suited to low-light work and motion capture, featuring direct pixel readout (no line skipping or pixel binning) and uncompressed 4:2:2 Full HD and 4K QFHD output via HDMI, but it’s also great for still photography in challenging conditions, with a dynamic range of 15.3 stops and ISO settings to 409600. All three a7 cameras feature built-in high-resolution OLED Tru-Finder electronic viewfinders and tilting 3.0-inch 921K-dot LCD monitors. The a7 series features more bells and whistles than the Leicas.
The a7 cameras take Sony FE lenses (full-frame E-Mount), of which there are currently five, none as fast or as wide as the Leica’s (the Zeiss Sonnar 55mm ƒ/1.8 is the fastest, the Vario-Tessar 24-70mm ƒ/4 zoom the widest), but they do take you longer than Leica’s M lenses—there’s a 70-200mm ƒ/4 with built-in optical stabilization (none of Leica’s lenses offer that). The a7 cameras will also mount Sony E (NEX) lenses, automatically cropping to APS-C format to avoid vignetting with these designed-for-APS-C optics. You can also use Sony A-mount DSLR and legacy Konica Minolta Maxxum lenses via the LA-EA3 or LA-EA4 adapter (the latter incorporates a phase-detection AF system), and pretty much any other lens for which you can find an adapter. Of course, using the adapter and SLR lenses increases overall system size.
Speed Characteristics Of Full-Frame Mirrorless Cameras
With the rangefinder Leicas, you can look through the viewfinder to compose at any time, even with the camera switched off. The Sonys, with their electronic finders, must be switched on and awake for you to be able to see through the viewfinder. Being complex computers at heart, all digital cameras take a moment to "boot up"—there’s a bit of a delay between bringing the camera to
Speaking of batteries, when used in viewfinder mode (only the M Typ 240 has live view), the Leicas should be easier on batteries than the Sonys, which are in live view mode all the time, whether you’re using the eye-level EVF or the LCD monitor. Pro DSLRs, with their optical eye-level finders and large batteries, get a lot more shots per battery charge, because electronic viewfinders and live view eat up a lot of power.