MC lenses were introduced in 1966 to work with the TTL metering system of the newly introduced Minolta SRT 101. This series of lenses included a coupling lug on the aperture ring which contacted a meter-coupler pin on the camera body. This combination input the aperture preset by the user so that the TTL metering system could indicate the proper exposure for the match-needle display. MD lenses were introduced in 1977 for the Minolta XD-11 camera. This was the world's first camera to offer both aperture-priority and shutter-priority automatic exposure. To accomplish this important development, the aperture blades of the interchangeable lenses were redesigned to be lighter and the closing cam slit of each blade was reshaped to allow a fine degree of control. An additional lug appeared on the aperture ring to input the minimum aperture of the lens to the camera's exposure computer. In shutter-priority operation, the XD-11 and XD-5 cameras first computed shutter speed using the lens information (MD Lug), ISO film speed, and available light and indicated the number in the camera's viewfinder display. The aperture was then closed toward that aperture and a final light check was done through the closed-down aperture before the mirror lifted and the shutter operated. If the aperture was not set to the "green" minimum number or for some reason, it could not close to the proper position, the shutter speed was adjusted to provide the proper exposure. In order for this process to be successful resulting in a proper exposure, the aperture blades of the lens must be in the proper place and stabilized before the final meter reading was made. This was possible with the new, lighter, and redesigned MD lenses. It was not as predictable with the MC lenses. This is because the inertia of the heavier aperture blades caused them to close to a smaller size before snapping back to the physical stop set by the MC lens' aperture ring. Because of advances in programming and mechanics, today's X-700 does not rely on a real-time reading through the stopped-down aperture to establish exposure. However, for proper operation in Program mode, MD lenses must be used. MC lenses can be used in A Mode and manual modes with the Minolta X-700 as the aperture blades will be stabilized before the shutter activates to make the exposure. MC lenses can also be used successfully on any XG-series, X-370 series, or X-570 cameras.