I was really happy with my Canon EOS 20D and reviewing my images I saw that I was drawn to what is called available light photography. In short, it means using only the light sources that are already in the scene, and this mostly under difficult or low light. Prime examples are candid portraits, indoor concerts or evening and night photography. The latter was of interest to me. I like how cities change their appearance when the sun goes down and the only illumination comes from artificial sources.
Usually, taking pictures in low light can be accomplished with a tripod for static subjects. But I am an opportunistic photographer. I like to take long walks and shoot whatever catches my eye. So carrying a tripod was something I wanted to avoid. Besides, I do like the grainy, slightly blurry documentary look. So what I needed was a lens with a fast aperture that I could use in low light. Still a student, I could not really afford one of the fast wide angle prime lenses. So I bought the cheapest prime available. A Canon EF 50 mm F1.8 lens (link to the successor) made out of plastic.
This was not really a lens for city or street photography, and on the EOS 20D it came to about 80 mm equivalent. So this was really more a portrait lens but it was all I could afford and I learned to use it. I also learned to enjoy using a single focal length, being constrained seemed to sharpen my own view. I used this lens from 2005 to 2011 and shot (kept) at least several hundreds of photos. Again, my records are still a bit spotty.