Originally posted by ChristianRock No, it's a different optical design from the M 50 1.7 (while still maintaining the 6 element double gauss structure that ALL manufacturers use or have used until recently - Nikon now being the exception).
And there was no K 50 1.7. The front section of the double gauss looks more similar to Nikon's designs. And the rear section has a different element joint (curved joint) compared to all other 50 1.8 and 50 1.7 designs.
Also, there is no such thing as a modern 50 1.8 design... unless you talk about the possibly over-engineered Nikon 50 1.8G which added some extra elements but doesn't seem to have the "pop" images with sharpness and contrast of the earlier 1.8D design. The one thing it did improve was bokeh, but other than that, it doesn't seem to be so popular with Nikon users in general. The "old school" 6 element double gauss design seems to still yield best results.
No K indeed but AFAIK, the DA50 IS a M/A/F/FA50/1.7, the difference of 0.1 is due to rounded blades.
I don't believe a second Pentax would have taken the trouble of redesigning a 50mm optical design for cheap lens as the DA50. They may have slightly tweaked it but that's it. Just as the DA35 is an FA35 in other clothes (and rounded blades).
Also, the DA50 is behaving quite like my A50/1.7 does.
A comparison would be interesting.
Either way this is no new design.