Originally posted by Femto1969 It does seem somewhat maligned online, but since the lens is frequently just given away, and the f/1.4 and f/1.7 only seem marginally better, I think I might save my $80 for this hobby outfit. If I end up relying on it, I may upgrade both bodies and lenses. But that's really what my Pentax 67 is for, anyway.
Do you like the f/2?
The 50/1.4's beginning with the Takumars were designed to offer a classic subject isolation, sharp in the center and a bit soft at the edges, with good bokeh (though they are quite sharp by f/4).
The 1.8/1.7 50's were specifically designed for flatwork, that is, taking a photo of a flat surface like a piece of paper with the camera mounted vertically on a copy stand. Flatwork was important before the advent of scanners and computers. The M50/1.7 is sharp edge to edge. We've adopted it's characteristics today as superior since sharpness across the frame is the contemporary style (Retina displays promote this style).
The 50/2's were less expensive, general purpose lenses that are still quite good for what they are. They usually have a simpler optical design with fewer elements than the faster lenses. The price delta for the M50/2 is more related to oversupply versus demand than a true quality statement, IMO. My CON for the M50/2 is open aperture focusing with old eyes. The more light the better, so Ipaid up for a 50/1.2 (which actually is inferior to the 1.4 until f/5.6).
You can examine the three optical formulas for the M lenses (actually all the normals) at the link below. Click on 'Optical Formula' in the lower box for each lens.
Pentax Normal Prime Lenses