The Canon 50mm f1.8 STM is a direct update to the inexpensive standard 50mm f1.8 EF lens. The STM version replaces the standard focusing motor with Canon's stepping motor technology. This has a smoother, quieter auto focus performance.
A underlying difference to the previous version of this lens, build quality is good, with high quality plastics used for the lens barrel and a metal bayonet. Despite the higher build quality, this optic still only weighs 160g.
My favourite part of this lens is the amazing Bokeh you can get. The high f stop of 1.8 is so good for them blurry backgrounds but is also amazing in low light situations. I took the lens out with my Canon 100d DSLR to the streets to test it in a street photography environment. This is a real test for the auto focus.
If you followed my instagram you'd know I'm a Black and White photo fanatic and B&W street photography is my thing and the lens stood up to the challenge. The autofocus is so quick and snappy. Very rarely did it disappoint. 9/10 my subjects where in focus and as a street photographer this isn't always an easy task.
My only small gripe if that is that even the the focusing motor is quieter than the predecessor, it is still audible and when trying to be invisible as a street photographer this can be annoying.
Even though I'm a big Black and White photographer I can still appreciate the great colours I could create using the lens.
Overall I love this Lens. It is a great piece of kit that all Canon users should have in their kit bags. For portraits and street photography and all kinds of photographers.