I am sorry because i am not knowing much, all of i know is that there are two kinds of CCTV Lens, one the focal distance is fixed,and the other one can be varifocal.
You can find the fixed focal distance CCTV lens on
http://www.surmall.com/cctv-security-products/cctv-lens.html
,and the distance is between 8mm to 25mm, there are also some varfocal lens.