Carl Zeiss Mirotar 500 mm f/ 4.5 C/Y Lens

Incredible sharpness and even illumination.

Weaknesses:

Size and weight make this slightly unweildy though the carrying handle helps.  A tripod is a must unless you use this with a digital SLR like the Olympus E-M1 III which has sufficient IS to allow this to be used hand-held. The absence of the Zeiss T* coating can be an issue under difficult lighting conditions, such as where you are photographing directly  into sunlight or with very bright light crossing the plane of the front element, as a reduction in contrast and control of flare can become an issue.

Of course, the bokeh of a mirror lens is an issue for many people but this lens handles it better than most.  I have a photo of this lens alongside my Yashica ML 500 f8 - the contrast in size speaks for itself!

Comments:

This is an amazing piece of optical and mechanical engineering that goes back to the late 1960s and the use of this lens on the Contarex.  The mount was adapted to a C/Y mount for use with Contax and Yashica SLRs post-1975 - only 215 were ever built.  The Contax 500mm and 1000mm Mirotar lenses are the only ones in the Contax Zeiss range not to have T* coatings, reflecting their earlier Contarex origins.