Received my Tamron 17-70mm today...

Dennis wrote:

Lettermanian wrote:

BeatX wrote:

Uhh.. That Tamron 17-70/2.8 is big! I mean it looks like similar size to any 24-105/4 FF zoom lenses (?)

A 2.8 lens is still a 2.8 lens in terms of light gathering, so there's not a direct comparison to a 24-105 f4.

You've been around here a long time (long enough to have read plenty about equivalence) you can't really believe that ?

Dustin Abbot states it succinctly enough in his reviewof the Sony version of this lens:

"There’s no question this is an extremely useful focal range, going from quite wide (25.5mm full frame equivalent, to telephoto (105mm). This obviously gives you a great deal of framing options, and, while the depth of field is more equivalent to a full frame F4 lens, the F2.8 aperture will always have the light gathering capability of an F2.8 lens (regardless of whether attached to APS-C or Full Frame), meaning that the B070 has certain advantages over a full frame 24-105mm F4 lens."

There's no ff lens in any current system that gives 450mm-equiv non-cropped images at the size and weight of Fuji's 70-300.

Yeah, that's where I kind of get stuck, too. I don't mind having a bigger lens at home for running outside for opportunistic wildlife photographs. But I really like the idea of a small, light kit I can travel around with and have up to 300mm APS-C equivalent. My Sigma 100-400 isn't all that big, but considerably bigger than the Fuji 70-300. If Nikon came out with a killer 70-300 lens for Z I could contemplate cropping but then I'd need a pricey Z7 II for the resolution and the lens would have to be very sharp to compete with the Fuji after cropping down to APS-C size.

So even though a lens like the 17-70/2.8 (or the 16-55/2.8) makes me question whether it's not just better to go FF with an f/4 zoom (same argument to be made for f/1.4 primes versus f/1.8 for FF), I can see an easy case for it when it's just one big, equivalent lens and the rest of the kit is smaller.

- Dennis
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