50mm is the so-called "normal" lens. You might choose a wide or a long lens for either the look it gives you, or for practical reasons. Or you might choose a 50mm because it does NOT give you a certain look, or because it is the only focal length that can work, given the subject and the space you have to work in.
If you are using a fast 50mm lens, like a 1.8, 1.4 or 1.2 the speed of the lens is usually the main reason to use it — for the way it throws the background out of focus.
Bottom Line: Use a 50mm lens because you want to avoid the more stylized look of wider and longer lenses, or because it is the only practical solution.
When you shoot with a general-purpose zoom, you may zoom to roughly 50mm without thinking much about focal length.
This summary of 50mm as a focal length suggests that it is rarely a chosen lens (other than a high-speed 50) — that it is generally a compromise lens. I asked a full-time pro friend about this, and he said he hasn't had a 50 on his camera in 30 years. A survey sample of one is not accurate, but you get the idea.
Left
Right
You are in a booth at a restaurant and need a photo of the person across from you. A wide-angle gets too much background, a tele gets too close. Use 50mm, same as in panel 2.
55mm, 24-105 zoom, f6.7, 1/125
You need a photo of someone in a car across from you - A wide-angle gets too much background, a tele gets too close. Use 50mm, same as in panel 1.
50mm, 24-105 zoom, f5.6 1/90
You want a shot with a certain amount of background in it. To get the face this big with this much background you would need to shoot from too close too use a wide angle — the big schnozz effect. You can't use a tele unless you put the subject on a ladder. No ladder? Use 50mm.
50mm, f5.6 1/45
Geometry dictates 50mm lens. You want enough window frame to show she is inside. A wider lens will show too much detail outside the window. You can't shoot with a tele because you can't get far enough away. Use 50mm.
50mm, f2.8 1/60
Let's say you have a certain vision for a shot of a woman in the woods and you want a certain balance of face and background, with a fairly close image of her face. Once again, you can't get close enough with a wide angle without distorting the face too much; the tele flattens the face in a way you don't like. Use 50mm.
You want a portrait that seems very "normal" that doesn't call attention to any technical aspects of photography. Sometimes 50mm will give you that "innocent" look.
You want a certain size to the log cabin pattern behind the subject. With a wide angle you get too many rows of logs, and they get distorted. With a tele you can't get the person and the logs in focus. Use 50mm.
You want to shoot a person through a window, juxtaposed with something reflected in the window. In cases like this, often a wide or long lens won't work and 50mm does.
You are in a booth at a restaurant and need a photo of the person across from you. A wide-angle gets too much background, a tele gets too close. Use 50mm, same as in panel 2.
55mm, 24-105 zoom, f6.7, 1/125
You need a photo of someone in a car across from you - A wide-angle gets too much background, a tele gets too close. Use 50mm, same as in panel 1.
50mm, 24-105 zoom, f5.6 1/90
You want a shot with a certain amount of background in it. To get the face this big with this much background you would need to shoot from too close too use a wide angle — the big schnozz effect. You can't use a tele unless you put the subject on a ladder. No ladder? Use 50mm.
50mm, f5.6 1/45
Geometry dictates 50mm lens. You want enough window frame to show she is inside. A wider lens will show too much detail outside the window. You can't shoot with a tele because you can't get far enough away. Use 50mm.
50mm, f2.8 1/60
Let's say you have a certain vision for a shot of a woman in the woods and you want a certain balance of face and background, with a fairly close image of her face. Once again, you can't get close enough with a wide angle without distorting the face too much; the tele flattens the face in a way you don't like. Use 50mm.
You want a portrait that seems very "normal" that doesn't call attention to any technical aspects of photography. Sometimes 50mm will give you that "innocent" look.
You want a certain size to the log cabin pattern behind the subject. With a wide angle you get too many rows of logs, and they get distorted. With a tele you can't get the person and the logs in focus. Use 50mm.
You want to shoot a person through a window, juxtaposed with something reflected in the window. In cases like this, often a wide or long lens won't work and 50mm does.
