Wide advice?

Hypermodern · 2018-04-26T07:07:11+0100

Hello all, been a Pentaxian for a few years (K50 and K3ii) but only joined the forum recently. I need some help... I would like a lens to bridge the gap between my Sigma 30mm f1.4 (old version without HSM, picked up because when my babies became toddlers I needed something faster than the 35mm f2.4 for indoors), and the 10-17 fisheye (so far used mainly for fun architecture and baby photos). I would like something wider than the 30mm but fast enough that I can still use it indoors. Apart from baby photos I do as much opportunistic street as I can whilst pushing the buggy and there is the small matter of my brother's wedding coming up, it's the small registry office bit before the big day and he wants some ceremony/family formals/couple portraits. I mostly shoot primes, but I'm not averse to a zoom. I do have the 18-135mm but I find it's not fast enough for moving targets indoors. I've been looking at the Sigma 17-50 f2.8 but not sure if this is too big, the equivalent Tamron but maybe this is just the poor cousin of the Sigma, the 21mm Limited but a bit worried about f3.2 indoors, I had thought about the DA 12-24mm but I'm not going to be a landscape photographer any time soon. Help! tl;dr - need lens for APS-C wider than 30mm, fast enough to shoot moving targets indoors.