<p>to awnser this question, it does not take much, really.<br>
you need a lens as wide as you gotta need it.<br>
period.</p>
<p>you do not want to carry heavy zooms because you can't, won't or are a cry-baby?<br>
get a 20mm so you will not miss out on anything.<br>
yeah, it is not a zoom, and you might fall 2mm of focal lenght short, but atleast you got the shot and that is all that matters :)</p>
<p> </p>