Originally posted by twitch Mind you I don't think the DA21 is very good either, seems Pentax has trouble designing good lenses around this focal length.
I agree, the DA15mm f/4 has problems competing against my sigma 8-16mm f/4.5-5.6 at 15mm. Lenses wider than 28mm have always been problematic for lens makers in general - pentax isn't alone here. However on the 645D the 25mm f/4 actually is quite an impressive piece of glass that competes favourably against competing medium format ultra wide lenses from Leica, Schneider and Mamiya. On the 645D the lens is a 19.5mm equivalent, on full frame 645 it is a 15mm lens in 35mm terms, IMHO pentax
can make a wide angle lens worth a damn - What consumers are willing to pay for it is holding them back.