The EF 50mm f/1.8 II replaced the EF 50mm f/1.8 in 1991. The original (now discontinued) Canon EF 50mm f/1.8 lens came equipped with a metal lens mount, distance scale, IR focusing label and separate manual focusing ring. The current Canon EF 50mm f/1.8 II lens has a plastic lens mount and is missing a distance scale, IR focusing label and dedicated manual focusing ring. Instead the manual focusing ring has been replaced by a very small thin focusing ring on the front tip of the lens. However the lens does not suffer from rotating front lens element and can be used with polarizing filters. The optics for both lenses are identical, with 6 elements in 5 groups and a 5 blade diaphragm. The 'nifty-fifty' has a 52mm filter thread.
The 50mm focal length, when used with a 35mm film or full-frame sensor, has been widely considered to match the perspective seen by the human eye. When pairing the EF 50mm f/1.8 II to a Canon DSLR with an APS-C sized sensor, photographers must apply a focal length multiplier (also known as a crop factor) in order to get the effective 35mm field of view equivalent. Most entry level Canon DSLRs come with a crop factor of 1.6x, which effectively turns the 50mm focal length into a 80mm field of view (50 x 1.6 = 80mm).
Because of its low price and sharp optical quality, this lens has earned the nicknames 'nifty fifty' and 'plastic fantastic'. When shooting at f/1.8, it offers a very shallow depth of field which is beneficial for isolating subjects against a blurred background (bokeh).
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