cropped sensor

With image quality getting closer all the time between crop sensor and full frame cameras, I am starting to wonder whether an amateur photographer would ever need to make the jump to full frame? After all, full frame cameras are much heavier to carry around and much more expensive, particularly...

Can anyone please tell me for sure if i need to apply the 1.6 crop factor to this lens as it is specially made for a cropped body as someone has pointed out ? which would make it roughly 16-32mm by my maths on a Canon cropped body?. Or not as its built specially for the ultra wide to be...