
What are the best lenses or focal lengths for street photography?
Is there a perfect lens for street photography?

Primo, there are no rules. You can use whatever lens you prefer in street photography.
I generally find that (for me) I prefer a 28mm lens on a point and shoot camera (or when using the LCD SCREEN) or a 35mm lens on a camera with a viewfinder.

For example, the RICOH GR has a 28mm integrated lens. I like it because I can get very close to my subjects (by extending my arm).

Phone Street Photography?

If you shoot on an iPhone or a phone, the default lens is roughly a 28mm “full frame equivalent”.

Street Photography with viewfinder cameras

For shooting on my Leica, I prefer a 35mm Lens (I use the Leica 35mm Summicron ASPH lens) because it is wide enough, but not too close. Also, because I wear glasses, I cannot see the edges of the viewfinder on a 28mm lens.
Learn more: LEICA MANUAL >
DSLR STREET PHOTOGRAPHY LENSES

I started serious street photography in 2009, with my Canon 5D (version I) and a Canon 35mm f2 lens. I shot everything black and white, RAW, and P (program mode), and center point autofocus. Like Henri Cartier-Bresson, I would wait for an interesting background, and wait for my subjects to enter.
For me on a DLSR, 35mm lens was ideal for “full frame.”

I like to shoot in P PROGRAM mode for street photography settings. Why? I like to “Set it and forget it” and focus on composition:

Telephoto / Zoom Lenses for street photography?

BRAZIL. Sao Paulo. 1960. © Rene Burri / Magnum Photos
Rene Burri shot his famous rooftop photo in Brazil with a telephoto lens.
Saul Leiter shot a lot of his phenomenal color street photo shoot with a telephoto lens.

For myself, I prefer shooting with a wide angle (prime, non zoom lens) because I like to get physically closer to my subjects.
To me, with physical proximity comes emotional proximity.
But it depends what your personality is, and what your aims for street photography are.
If you want to be more creative with your street photography, I think having “creative constraints” help more with creativity. Most street photographers I know excel using 28mm or 35mm Lenses.
Of course, just experiment with zoom and telephoto lenses, and see if you like them for street photography.
There are no “rules” in street photography, only tips and suggestions.
50mm in Street Photography?

Henri Cartier-Bresson popularized the 50mm for street photography. Why? It doesn’t distort the frame.

But to me 50mm is boring. Not dynamic in street photography.
Try it out though. Most people tend to prefer 35mm lens.
But doesn’t the human eye see as a 50mm? Not quite.
The human eye sees roughly a 40mm perspective.
But once again, experiment and see if you like it.
I also recommend NOT to get a f1.4 lens in 50mm. Get the smallest, lightest, most compact 50mm possible. 50mm f2 is ideal.
Conclusion

Experiment with different lenses and focal lengths in street photogrpahy until you find something that suits you. Then my recommendation,
Stick with one camera, one lens in street photography for at least 1 year. Then you will truly grow, develop, and master your camera and the “decisive moment” in Street Photography.
BE STRONG,
ERIC