A rectilinear lens will have been corrected for inherent optical distortion, but it will have perspective distortion when raised or lowered from level. darinwc is quite correct to state that brand-name wide-to ultra-wide primes are pretty darn good — much, much better than what was available in the 1980s and 1990s. But it's important to understand and differentiate the types of distortion. Not even Zeiss is immune from the silly twists and turns at the edges that come about from odd shooting angles.