> Does anyone have any experience or comments on the following lenses? > > Sigma Zoom Telephoto 170-500mm f/5-6.3 APO Aspherical for Pentax AF > > http://www.bhphotovideo.com/bnh/controller/home? O=productlist&A=details&Q=&sku=121742&is=REG > > Sigma Zoom Normal-Telephoto 50-500mm f/4.0-6.3 EX APO RF Autofocus > Lens for Pentax AF > > http://www.bhphotovideo.com/bnh/controller/home? O=productlist&A=details&Q=&sku=192448&is=USA
Hi Tom I've not used either but I have the 135-400 APO which is quite good, it's not a match for the 300 f4 APO even when it's fitted with the 1.4x EX converter but I never expected it to be. I believe the 50-500 is the better of the two but there again it's considerably more expensive being the EX lens designation. The 135-400 may not be the sharpest of lenses but appears to have a complete absence of CA on film. The worst feature for me is the amount the lens extends at it's maximum focal length, present on 135-400, 170-500 and 50-500. John
