Go wide! Go wider!! Go as wide as you can without going too wide!!! This is how I think about the 20mm lens and, to be specific, the classic 20mm f/2.8 Nikkor in both auto and manual focus. In my long experience with this lens — I have used it in its MF and AF versions as one of my primary working optics since around 2000 — I have found it to be a special lens in particular and generally as wide an angle as one can get without entering the realm of special effects. Lenses wider than 20mm can come in handy for unique perspectives and situations, but rarely for every day use.