Manual Control Options
The Leica M8 is a fully manual camera. Aperture, shutter speed, ISO, white balance and focus are all easily set manually.
Focus
Auto Focus
The Leica M8 has no autofocus. Leica-M lenses have no provision for autofocus. The rangefinder system at the heart of the M-series is fundamentally manual.
Manual Focus
The Leica M rangefinder works by triangulation. As the user adjusts the lens focus, the image in the bright rectangle superimposed at the center of the viewfinder shifts. When it matches the background exactly, that spot is in focus. The moving image is projected by a mirror in the rangefinder window. The mirror pivots as the lens' focus mount turns, and the camera measures distance through the angle at which the rangefinder mirror is pivoted. The Leica system is built to a close enough tolerance that the system can accurately focus the 50mm f/1.0 Noctilux and the 75mm f/1.4 Summilux.
In practice, the rangefinder allows users to nail focus exactly on a single point, and is more accurate than SLR focus for wide-angle lenses. Its great drawback is that it does not show depth of field. It depends on user skill, but it's not likely to be nearly as fast as autofocus systems.
Exposure
The M8 offers manual and aperture-priority exposure modes. The manual mode shows three symbols in the viewfinder – one to indicate underexposure, one correct exposure and one over exposure. The user can shift the aperture dial and shutter speed dial to light up the signal for correct exposure. The exposure compensation control can be set from 3 EV above to 3 EV below the metered reading, in 1/3-EV steps.
Metering
The M8 has a silicon photodiode that is pointed at the camera's shutter. One of the shutter's metal blades is painted light gray, and the sensor takes a “heavily center-weighted” reading off the shutter. Apparently, the color of the blade influences the metering pattern. The Set button calls up an exposure compensation control. A second light meter peeks from a small window along the top edge of the camera.
It's clear that spot and evaluative metering could have been incorporated in this camera. Leica knows how to do that.. It's not entirely clear why they aren't on a camera with the amenities of the M8.
White Balance
The Leica M8 offers automatic white balance, begging the question of whether it's possible to exclude it from a digital camera. The M8's presets are: Daylight, Flash, Cloudy and Shade. The M8 also takes manual white balance readings, and did a fine job with a Leica staffer's crisp white shirt. Users can also set Kelvin temperatures directly, from 2000 to 13,100K.
We used the Auto setting and the manual setting. The manual setting was superior under mixed fluorescent lighting, but the Auto setting was very close.
ISO
The M8 even has odd-ball ISOs: 160, 320, 640, 1250 and 2500. Anyone for High-Speed Ektachrome or Kodak Super-XX? We prefer to see ISOs in 1/3-EV increments, and these are full steps, restricting the user's control over noise to some extent. The M8 does not have an Auto ISO setting.
Shutter Speed
The M8's manual shutter speeds run in half-steps from 1/8000 to 4 seconds in half-steps. In auto mode, the M8 sets speeds steplessly from 32 seconds to 1/8000. There is no practical limit to the length of time exposure the M8 will allow when set to Bulb, according to Leica.
Aperture
M-series Leica lenses have manual aperture controls. Since the lenses are used only for taking the image, not focus or viewing, the iris stays where it is until the user changes the setting. The arrangement also removes the need for any mechanical or electronic link between the meter and the aperture. The meter simply sets the shutter speed for the intensity of light it measures inside the camera – it doesn't matter whether its from a bright environment seen through a small aperture, or a dark subject seen with a wide f-stop. Because they aren't linked to anything, the aperture rings can be set anywhere between f/stops, though the rings click into place at the standard settings.
