Rotator cuff injuries cause pain in your shoulder and upper arm. The pain may be most noticeable when you reach up or out. When you turn your arm as you lift it, the tendons are more likely to rub against surrounding structures.
The essential difference between the original series of AF Nikkor lenses and all AF lens types introduced subsequently, from the AF-D versions onwards (see below), concerns the compatibility of a particular lens with Nikon's enhanced Matrix metering system known as 3D Matrix metering that was introduced during 1996.
Sensor size and image quality also varies, with most mirrorless cameras using sensors from the one-inch-types used in the Nikon 1 series, to the full frame sensors of the Sony A7 line. As such there's a mirrorless camera out there for the needs of anyone whether you want pocketable or ultimate quality.