Full frame versus crop sensors
We are talking here about the 50mm lens. This is however for an FX camera, a full frame camera. These have sensors that are just a large, as the analog camera's used to be with their negatives.
Most hobby cameras and even the better ones have a crop sensor. These sensors are smaller. So for a camera with a crop sensor the equivalent of a 50mm is a 35mm. These lenses are just as good and just as fast and just as cheap as the 50mm lenses are.
So if you have a camera with a crop sensor you can appy this whole story to a 35mm lens.
The 50mm standard lens is also called the nifty fifty, or the fantastic plastic. These lenses are relatively cheap and very very good. And evenmore, they let through a lot of light. f1.8 and if you want to spend more, even f1.4 is possible. But then it gets more expensive and heavier.
There are a lot of good reasons to buy one if these lenses, not matter what brand you use. Here are five, like discribed by Cole's Classroom. You can learn some great stuff there by the way.
It is cheap.
Who does not want to buy a very sharp and fast lens for little money?
It is fast.
You can open a 50mm up to f1.8. Why would you want an f1.8? Because you can use much faster shutterspeeds! Which means you can take sharper pictures in less light. No zoomlens can tip at that. Even the very expensive zoom f.2.8 lenses that weigh a ton let through half as much light as the 50mm. Besides you can keep your ISO settings low. Higher settings lead to more noise in the picture. Tho in black and white that is not really a problem, cause it resembles grain.
It is small and it hardly weighs anything.
The 50mm is a small lens and it is light. So you can take it with you easily. And it is easier to take pictures cause you do not attrackt that much attention as with a long zoomlens.
It can be used for almost anything.
It is a great lens for almost anything you can photograph. Landscapes cause it has no distortion and covers as much as the eye can see. Portraits and when you keep a bit of distance and a large opening you get this lovely blurry background so all attention goes to the face. Close by pictures. Tho it is not a macro lens you can get quite close and take a relatively large picture of small things. For street photography, cause it is easy to handle and does not attrackt much attention. Henry Cartier Bresson did not use anything else than the 50mm. And when there is little light, this guy is your man.
It makes you take better pictures.
With the zoom you turn till the subject fills your view and you press the button. But with a prime you cannot zoom. If you need to zoom, you have to use your feet. So you need to look what is in de viewfinder and there will be more than just your subject. That means you have to think of how to 'compose' your picture. Or, in case the subject does not fit in your image, you need to decide what to leave out. And getting aware of this makes you make better pictures for sure.