M - introduced with the MX/ME series, generally smaller and lighter than the K series for the same focal length/aperture.
I think many M lenses had newer designed optics.
A - Adds an AE aperture setting to K- or M-specs, for cameras with shutter-priority or programmed exposure modes. These came in after I switched from working in camera shops to being a computer programmer, so I don's know the models or dates.
The aperture coupling lever is liner too, the K/M aren't. Many designs were borrowed from the M series, plus a few high quality A* & newly designed high quality zoom lenses. There were 2 series belonged to the A series lenses:
1) Super A/Program (the most advanced), Program A/Plus, A3000 2) P50/5, P30/3, P30n/3n, P30T/3T?
F - Adds autofocus to A-specs.
Many designs were borrowed from the A series, but with many holes in the line. FA series is more completed.
regards, Alan Chan
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