This particular 50mm lens is a popular favorite among Pentaxians. Reasons are abound, and include low price, high availability, small size, sharp photos, decent bokeh, and, well, it's probably one of the best 50mm lenses of the era available for Pentax. Because of its diminutive size, I have paired it with the 1.4x-S teleconverter which almost doubles the weight in order to get to a short telephoto focal length of 70mm. Why do this? Because it can be done. Also, I kind of like the short-tele field of view that 50mm can bring, and initially I was interested in what effects a TC can have on such a lens.
Anytime a teleconverter is attached to the back of a lens, it should be considered a *different* lens because the optical formula is now different. In fact, many things are different including physical dimensions, field of view, fastest aperture, and potentially the application of the lens. So, sticking with that strategy, the story will continue (until this series is finally complete) which treats this combo as a separate optic.
As stated before, the lens is 185g (0.4#) and, focused at infinity, 31mm long (1.2 inches) and with the teleconverter attached, the combination weighs 305g (0.67#) and 65mm (2.5 inches). The fast aperture of f/1.7 is about average for normal lenses of the day, and the addition of the TC adds another stop, so the actual fastest aperture is f/2.5. The lens bears the usual aperture ring and a rubberized grip on the focus ring, and has 6 aperture blades and 49mm filter threads. Minimum focus distance is 45cm (18in) producing 1:5 reproduction ratio (0.2x). The TC increases magnification without reducing minimum focus distance.