I have the Nikon 50mm f/1.8. It was the first lens I bought along with my D7000 (I opted for body only cause I didn’t liked the kit lens it comes with). I had my reasons to pick up a prime instead of a zoom lens.
1. Small and light, the camera I picked up is quite sturdy and definitely on the heavier side in the family of cropped sensor cameras, so to start with I wanted a lens that was light itself.
2. To keep me on my toes. I know zoom lens has a lot of freedom, you can change the frame by just zooming the lens in or out, but I think it makes you lazy. On the other hand for a prime lens, if you want to change the frame you must move. I personally feel this made me put in more effort in order to frame better shots.
3. Shallow DOF. This has to be the most beautiful aspect of this lens, blurring the background with beautiful bokehs and focusing only on the subject.
4. Fast Aperture – f/1.8 compared to the stock lens with f/3.5 at wide end. Even though I would preferably shoot at f/2.2 it is still faster than the zoom lens. This also means the lens is brilliant for low light photography.
5. It is so freaking cheap!
If you have the money you could opt for the 50mm f/1.4, but the f/1.8 itself is nothing short of a magic lens.
If you have an APS-C, the effective focal length is slightly longer (75mm on the D7000)