Telephoto lenses can be incredibly useful, but how is it different from other lenses, and when should you use it?
What Is a Telephoto Lens?
A telephoto lens is a lens that appears to magnify distant objects. To do that, they need to have a focal length longer than that of a normal lens, or a lens that approximates the optical qualities of the human eye. A normal lens has a focal length of between 40mm and 58mm on a full frame camera so any lens with a focal length longer than 60mm can be considered a telephoto lens. The longer the focal length, the more magnification there is.
The most common telephoto zoom lenses have a focal range of 70mm to 200mm. Any lens with a focal length longer than about 300mm can be considered a super telephoto lens as well.
On a crop sensor camera, telephoto lenses are those with a focal length longer than about 40mm, although the magnification will be minimal until about 50mm.
Let’s look at this in action. This photo was taken at 50mm, a normal focal length, on a full frame camera. The photo appears pretty similar to how things look with your eyes. The other photos were all taken from the same spot with a crop sensor camera; I don’t have a long enough full frame telephoto to really make the point clear.
This photo was taken at 45mm using a crop sensor camera. The full frame equivalent focal length is 72mm. You can see how the image is a little tighter on the car.
This photo was taken at 85mm, equivalent to 136mm on a full frame camera. Now the car totally fills the frame.
This photo was taken at 135, equivalent to 216mm on a full frame camera. We’re incredibly close to the car compared to the normal photo. It’s impossible to fit the whole thing in the picture.
How a Telephoto Lens Affects Your Images
The main effect of telephoto lenses is that, like a…