Originally posted by Flaco I was at a local photo store today they had one in stock. One of the employees said he liked the 1.7 better then the 1.4. Said he felt the 1.7 was sharper then the 1.4. So I was wondering what people that have USED BOTH thought about it.
I owned M50/1.7 which is optically the same as A and FA. Also, I currently own A50/1.4 which is optically the same as FA50/1.4. Here is my experience:
M/A/FA 50/1.7 is sharper than A/FA 50/1.4 for the good reason: 50/1.4 has (intentional) imperfection: field curvature and spherical aberration are more pronounced than with 50/1.7 and Pentax itself is NOT recommending 50/1.4 in combination with extension tubes or close-up lenses, while 50/1.7 is fine to use for macro work. However, due to pronounced field curvature and spherical aberration 50/1.4 has one big plus: "creamier" bokeh. Since 50/1.7 is more "technically correct" it results in better sharpness while producing bokeh that some people find to be somewhat "harsh", although it is very good as well. (FA35/2 AL is getting similar comments about the "harsh" bokeh for the same reason, I own FA35/2 and I do not complain.)
Bottom line: both are excellent lenses. 50/1.4 is better if you are after smoother bokeh and if it is acceptable to shoot at f/4-f/11 for optimal sharpness. 50/1.7 will serve you better if you are after improved and more uniform sharpness across the frame at all apertures, and if you want to combine it with extension tubes or close-up lenses for macro work, assuming you are fine with technically cleaner (not bad!) bokeh.