When we thinking about long lenses verses short lenses, the first thing that comes to mind is how close we can get to the subject. Or really how far we can be from the subject while shooting.
Look at these two images, shot from the same location, one at 70mm and one at 200mm. See how different the same background looks?
But there are a couple of other important factors that come into play, which we often forget and don’t use to our advantage.
One of those things is compression. By compression I mean that a when you take an image with a longer lens, items look closer together front to back than they do with a shorter lens. This can be use to make things seem right next to each other when it might be dangerous to have them right next to each. For instance, they use this in film in car chases. By filming one car chasing another with a long lens the trailing car can be a safe distance from the front car, but look like it is right on top of them.
You can see how this could be used in model photography. Say you wanted a model and a dangerous animal in the same image. Well if you used a long lens she could be a safe distance from the animal, but still looks like it was right behind her.
This is also related to how a long lens has a wider/long area that is in focus. With say a macro lens at 35mm, the area in focus is less than an inch at a 2.8f stop. On a 200mm lens that same 2.8f will put a foot in focus. This lets you have your whole subject in focus, but everything else blurry.
Long lenses just look different, and understanding why helps you use them well. Next we’ll talk about angle of view and long lenses.