Originally posted by mille19 AF.C Tracking test
Is 60-250mm F4 v 70-200mm F2.8 a fair comparison ?
Originally posted by RockvilleBob A good point. Why not compare AF using a common lens say Sigma 70-200 2.8
I think it is a fair comparison, except like I said that a DX Nikon should have been used.
I know that Nikon AF is optimzed to perform well with the 70-200/2.8G (and $3000+ lenses), the major workhorses for professional AF.C work.
The 60-250mm may be the closest match assuming Pentax used this lens to validate their AF.C too. Provided both are used equivalently (e.g. at 135mm F4 vs. 200mm F5.6; or with a Nikon DX body, both at 200mm F4).
If the Sigma 70-200 2.8 performs faster on the Pentax then by all means, use it! But one wouldn't want to cripple the Nikon by using the Sigma lens. AF.C tests are system tests combining both, best body and lens, for either system.
BTW, a few screw drive lenses like the FA* 300/4.5 which I own already are blazingly fast on the K-5. With the K-3, it should be faster even. It could be a stunning performer in an AF.C test. Maybe worth to give it a try.