Thanks, Terry, that makes sense. It's surprising though that, in their reviews of the lens, neither DPRreview nor SLRgear mention this.
Originally Posted by TEBnewyork
The lens focuses by moving the entire optical assembly, with a maximum increase in length of a mere 3mm.One would think that the lack of continuous auto-focus would warrant a mention in a supposedly thorough review.
I'm even more surprised that this is also the case with the even lighter 17/2.8.
Originally Posted by Vivek
Just another example of discrimination against those of us who prefer primes.