The Nikkor 18mm f/4 is a wonderful lens and one I always lusted for as a young aspiring photographer in the '70s. Then I used it occasionally as a loaner in the non-AI first version and decided to buy it for myself as soon as possible. Which due to circumstances in life one never can control, took almost 2 decades

Richard has mentioned most of the lens characteristics already, thus I'll only add a few images of my own to illustrate other aspects of the 18/4 not generally known. The 18/4 has the ability to do ultraviolet (UV), which is most unusual for a superwide lens, and it excels in IR as well. It has
no hot spot in IR, which makes it quite unique.
First, a few UV examples, taken either on Nikon D40x or D3200 with internal Baader U 'Venus' filter.