Hi Omer,

do you have a scientific application in mind? 

Hi Ahmed

I'am interested in surveying measurements ( Close range photogrammetry)

Fixed focal lengths lenses are best if you are after low distrotion. Zoom lenses are the worst offenders but usually have one focal length on the zoom range that has acceptable zoom characteristics. have a look at this site for distortion analysis on all mainstream dslr lenses http://www.photozone.de/all-tests

also there are standard techniques (available online) for quantifying the distortion and subsequently correcting for it.   

Dear Sharif 

Thanks a lot for invaluable information, the website is very helpful.