What Is a Telephoto Lens?

By Harry Guinness on June 14th, 2017

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 telescope, they magnify distant objects. Distant football players, small birds sitting in trees, and other similar subjects are all much easier to capture with a telephoto lens.

The flipside of this is that they have a very narrow field of view. To use a telephoto effectively, you need to stand well back from your subject. With a 70mm telephoto lens, you have to stand around 15 feet back from a human subject to fit them in the frame. With longer telephoto lenses, how far away you need to be from your subject to get everything in frame grows quickly.

It’s very easy to get a shallow depth of field with a telephoto lens; it’s one of the reasons they are so popular with portrait photographers. It also means that it’s very hard to get photos with a large depth of field. Even at apertures like f/11 or f/16, you still will struggle to get everything in the frame in focus.

Telephoto lenses appear to compress everything in the image. Objects that are distant in real life will appear closer together in the image. This is neither a positive nor a negative, just an effect you need to be aware of.

The Pros and Cons of Telephoto Lenses

Telephoto lenses are great for getting close to your subject without having to be physically close. You can’t walk into the middle of a football game or wander right up to a shy bird to take a photo so instead, with a telephoto, you can sit back snap from a distance.

Telephoto lenses take great portraits. The 70mm-105mm range is very very popular for them. Personally, I use an 85mm lens for most of mine.

While telephotos do everything they’re meant to do wonderfully, they do have a few downsides. They tend to be big and heavy. It’s just a side-effect of having a long focal length. This makes them awkward and unwieldy, even at the best of times.

You also have to be far away from your subjects to use a telephoto lens. When you’re outside, this is normally okay, but in any confined area, you might not be able to get enough distance to get your subject in frame.

Telephoto lenses also require faster shutter speeds to get sharp exposures. Even with a tripod, if you use a telephoto lens with a shutter speed lower than about 1/200th of a second you risk having camera shake in your images. This means they need a lot more light to get good photos; using a long telephoto lens at night is almost impossible.

What Telephoto Lenses are Available?

The majority of affordable telephoto lenses are zoom lenses, although you can get a few single focal length prime lenses if you want a specific portrait lens. Here are some of the best starting options for different cameras.

Canon

Nikon

A telephoto lens is one of the first purchases most photographers should make once they’ve master the kit lens. They’re necessary for a lot of popular fields of photography, like sports and wildlife.

Harry Guinness writes occasionally when he’s not busy skiing, sailing, partying, lifting weights, or otherwise dodging responsibility. His main areas of interest are himself, gin, and crazy people with interesting stories to tell. When people won’t pay him to write ill-thought-out opinion pieces, he covers photography, technology, and culture. You can follow him on Twitter.

  • Published 06/14/17
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