anybody with $180,000 burning a hole in their pockets? looking for a mega rare super-telephoto lens (only 20 ever built) ? look no further . . .

http://www.bhphotovideo.com/c/product/801201815-USE/canon_2527a001_super_telephoto_1200mm_f_5_6l.html

totally awesome . . . wouldn't fancy hiking around Doi Ang Kang with it round my neck though.

Looks like the type of thing that gets you sent to Guantanamo for 15 years.

^ i think you'd probably notice a little difference in IQ with it slapped on a pro FX body compared to a plastic toy bridge cam Oily . . .

(but i know what you mean . . )

F-number, just like focal length, does not depend on the sensor size. F-number is the focal length divided by the effective physical aperature diameter. However, since smaller sensors archive the same angle of view at a smaller focal length than larger sensors, then if you have lenses with the same angle of view and f-number, then the aperature diameter of the larger sensor lens will be larger.

("effective" essentialy meaning the size as seen looking through the front of the lens. The actual physical size will be less than the effective size, but it is the effective size that matters -- this correcystic for the placement of the aperature within the lens.)