Lock button on my "new" Tamron 28-75: what is it for?

<p>I don't have a lot of lens experience and have never seen this. Please explain this lock feature to me so that I don't try it in the wrong way, and break it on my first day with my new lens!</p>

<p>I think the lock button in question is to fix the zoom at the 28mm position. Otherwise there's a chance that the lens will accidentally twist and extend. It's really no big deal if this happens, and sometimes the zoom lock becomes a nuisance if you want to quickly change focal length immediately after lifting the camera and lens from its bag.</p>

<p>Personally I find this a reasonably useful feature, since I use a holster-type case for my camera. If the lock isn't used the lens sometimes drags against the case and extends the zoom. Extending the zoom by pulling on the lens barrel probably isn't too good for its mechanism in the long term.</p>

<p>Thank you, Rodeo Joe!</p>

<p>Renee, assuming that you are referring to the lock button in the lower left of the image in this link: http://www.juzaphoto.com/shared_files/recensioni/tamron_28-75_f2-8.jpg<br>

that apparently locks the zoom ring as Rodeo Joe points out. I don't have that Tamron lens, though.</p>

<p>Here is a link to the instruction sheet for your lens:</p>

<p>http://tamron.cdngc.net/inst/pdf/a09inst_1011_en.pdf</p>

<p>Rodeo Joe was correct.</p>

<p>Yes, that's it, Shun, and thank you Brooks for the link!</p>

<p>You have to think not once, not twice, but three times and then unlock it. It's to stop you taking bad pictures.<br>

Obviously I don't bother with it.</p>

<p>Dammit Nico! My button must be broken, or I'm not using it right then, 'cos it allows me to take bad pictures all the time.</p>

<p>Do you think maybe if I upgraded to the VC (Verify Composition) version, it might help?</p>