Originally posted by Lowell Goudge 
The zoom creep is not limited to tamron or this lens, but any design that moves the front group oout to zoom. My Old Vivitar S1 70-210 F3.5 did it also. Actually the lock would be more useful if it were a friction lock not a detent at minimum focal length.
As for seals and the rain. I think the lenses need to breethe a little, otherwise one such as this that douples its length would put a tremendous stress on the seals when you zoom out. better a little moisture in the barrel than some sucked into the seals
I'm not suggesting that the Tamron, as is, should have seals, but that I want a sealed lens like the internal-focusing 16-50mm F2.8. I've found the ability to shoot in the rain to be tremendously useful.
I also have never experienced zoom creep on any Pentax lens that changes its length (such as the 18-55mm, 50-200mm, etc) nor several other third-party lenses - only this Tamron and the Vivitar S1 70-210mm (which doesn't change its length.) I'm sure other lenses do it but it's not like every cheap zoom lens does it.
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