ive a opportunity to purchase a 16-35 F4..I already own a 17-35 F2.8....id have to sell the 17-35 to buy the former....anyone have experience with the two lenses......after all the buying and selling is done..I doubt Id have to spend any extra...perhaps $50-$100 at most

I like the idea of the VR..would be handy inside..the F2.8 on my 17-35 is only used if I have to....eg inside, as its a tad soft at the edges ..so I shoot at F4 or above if i can

I like the build of my 17-35.. and its length versus the longer F4 lenses ....

my main concern is contrast and sharpness of the F2.8 lens versus the F4 lens in real world use..not DXO scores..so has anyone used both..?