50mm

50 mm
full frame

that's the only lens you really need.
it makes your Dslr compact and efficient while travelling, it reproduces more or less what your eyes normally see.
you want to zoom in ? come closer
perhaps a wide over view ? take a few steps back, as you would with your real vision.

until they make us into cyborg, and replace our biological eyes with smart cameras, we are seeing about 42°.

it used to be the real "kit lens" of the analog age.
you buy a nikon F2 - get a great 50mm with it.

unless you're shooting extreem architectural shots, or landscape, you don't need anything shorter.
it has little if any distortion, durable and easy to use. and it can be fast. very fast.

You can produce stunning images with a good old fixed lens. Better for some video work even.

I have a few 50mm.
even the cheaper ones from canon are getting me excellent result, and the better, analog nikon one (with adaptor) produces exquisite result.

Canon 5D MK II with the 50mm canon 1.8
Jpeg original file

Canon 5D MK I + nikon 50mm 1.4 manual focus.