"CHROMATIC ABERRATION: None whatsoever! This is the second, astonishingly good trait of this lens! No other wide-angle lens I have ever tried has pulled this off, not even the ZF 18 (which shows traces of CA in the corners). Kudos to Samyang."

"…it is also a hair sharper than the Zeiss 18mm prime (believe it or not), and unsurprisingly it is way better than both Nikkor primes…"

http://forums.dpreview.com/forums/readflat.asp?forum=1030&message=36169192&changemode=1

"Photozone comparison shows the samyang to be slightly sharper than the canon, which is amazing. It also has a little less vignetting stopped down. Both do very well with CA. I can tell you that the microconrast and color are as good if not better than 16-35 2.8L II."

http://forums.dpreview.com/forums/readflat.asp?forum=1032&thread=36037552&page=1