At 18mm, central sharpness is excellent from f/2.8 to f/8, very good at f/11 and f/16 and soft at f/22. The edges are very good at f/2.8 and f/4, excellent at f/5.6 and f/8, very good at f/11 ...

The choice would appear to be between a faster lens or a more extended zoom. If the decision is made for the f/2.8 aperture, then we have a choice of one and it is, fortunately, fairly priced. For ...