C.P.U. - thanks for your info, but I think some people still need some sharing from others people opinion... Anyway, is it a correct place for me to ask about I thinking to buy a lens below:-

Canon 14mm f2.8 Mark 2

Using
Canon 5dM2
Canon 24-70 f2.8 M2
Canon 135 f2

I owned 16-35 m2 b4, finally I just sold it because I don't like the result of IQ - (after used it for 1yr+)

Cons - contrast, distortion & sharpness (corner)
Pro - ultra wide + zoom

the extra wide 2mm I know is not really important, but I believe will help. I read some review about this 14mm :

Cons - pricey, sharpness (corner)
Pro - widest lens (except fisheye lens), contrast, distortion

I need ultra wide lens for my trekking trip/leisure tour at least twice a year & in Malaysia normally ill using 24-70 & 135 only.

Please give some advice, I don't want to make another mistake again... Thank you!