Originally posted by kottier Usually, a longer focal length means a 'flatter' image. My guess is that the old lenses give a higher contrast, but that's my € 0.02. Examples are indeed welcome.
I doubt it's merely an issue of focal length or higher contrast. I have an old tele-takumar 300mm lens that has what is sometimes refered to, rather vaguely and inadequately, as the "Pentax pop." It's a rather subtle, intangible quality difficult to put one's finger on and not always appreciated or even noticed. But it does seem to be a characteristic of many Pentax lenses, even those with longer focal lengths. (I've heard it's present even in the old 500mm f4.5)
This is not the first time I have come across a complaint about the DA pancake lenses producing "flatter" images than other Pentax glass. Probably it is due, as a previous poster mentioned, to the compromises necessary to make the lens so compact. It would be interesting to know whether the old M series 40mm pancake suffered from the same defect.