<p>Within my first few years of wedding photography I discovered that the Tamron 28-75 would not focus nearly fast enough to get in-focus images of processionals or dancing subjects. It can't track well enough. It has great optics, but it focuses too slowly. In low light, it takes even longer to acquire focus.</p>
<p>IMO, focus speed is of extreme importance with wedding photography because of moving subjects and how many photo-worthy moments can happen suddenly. If your lens doesn't lock fast enough, you missed the shot. If your lens can't track the moving target, you missed the shot.</p>
<p>I bought the Canon 24-70 years ago, then sold it, then bought another and sold that later when I moved to primes. However, the focus was like lightning compared to the Tamron 28-75, and I can say without reservation that the faster focus allowed me to get many shots I simply could NOT hope to get with the slower-focusing Tamron 28-75. It tracked better, it locked faster, like night and day, the difference between Zt! and Zzzzzzzzzzzzzzzzzzzzzzzzzz....zzzzzzzz...t. But without any sound.</p>
<p>As a primary/solo photographer, I would not use the Tamron 28-75 for weddings unless I had no other choice. If my second shooter was using the 28-75 (if I had a second), I would expect many more out of focus images because of slow focus speed, and I'd never expect a good processional photo from them. However, if ALL they are shooting is static, nonmoving subjects with no time constraints, then it's a great lens for that.</p>
<p>And just for reference, a lot of photographers don't know how to use 24-26mm focal length so they are oblivious to the kind of perspective distortion it can destroy a photo with. I never recommend the 17-50/17-55 variants for that reason. Plus, the Tamron 17-50 actually focuses SLOWER than the Tamron 28-75.</p>