What Is a Telephoto Lens? (Why and When you Need One!)

What Is a Telephoto Lens? (Why and When you Need One!)

A telephoto lens makes far-way objects appear closer to the camera. But, do not think to pull out a telephoto lens only when you need to capture something in the distance. If you did, you would be missing out on some of the biggest reasons to shoot with such a long lens.

In this article, we break down everything budding photographers need to know about telephoto lenses.

What Is a Telephoto Lens?
A telephoto lens has a focal length longer than the diagonal size of the image it takes. In everyday language, it can be any lens that has a long focal length.

Depending on who you ask, some say this length is 70mm or greater. Others would not consider a lens as telephoto until 80mm or 85mm. And others do not use the term until the mid-telephoto range above 135mm.

Telephoto lenses can be zoom lenses, such as 70-300mm. They can also be a prime lens, such as 200mm.

To bring subjects up close to the camera, telephoto lenses need many pieces of glass inside. This often makes them large and heavy. It also makes them expensive.

The long focal length results in a narrow field of view. The angle of view of these lenses is between 30° and 1°. This is useful when you cannot get close enough to your subject.

What Are the Different Kinds of Telephoto Lenses?
Telephoto lenses can be further divided into sub-categories based on focal length.

Lenses between 85mm and 135mm are considered short telephotos. These can bring an object in close and create background separation but to less of an extreme. These focal lengths are popular for portrait photography, product photography, and event photography. The lens offers more background separation without requiring the photographer to stand too far from the subject.

A 135mm to 300mm lens is often called a medium telephoto lens. These focal lengths are among the most popular. They offer a significant reach without a high price tag.

Lenses above 300mm are typically also referred to as a super-telephoto lens. These lenses offer the most reach. If you use a telephoto lens on a crop sensor, it can reach a focal length as long as 1000mm. This also means that they have a narrow field of view, from 8° to 1°. They are often expensive and used by professionals. They are primarily for shooting sports, wildlife, or the night sky.

Due to their size, for using super-telephoto lenses, you always need a tripod. There might be image stabilisation in them. But you will not be able to hold them so steadily that your images stay sharp. Most oversized telephoto lenses have a tripod collar to help support the lens’s weight.

For a quick comparison, look at these images below. The first was shot at 165mm and the second at 300mm.

What to Know About Telephoto Lenses and Sensor Sizes
A 300mm lens on a full-frame camera is a 300mm lens. But change the size of the sensor in the camera body and the angle of view that the lens captures also changes.

A crop sensor, such as an APS-C sensor or Micro Four Thirds, makes a telephoto lens appear to bring the subject even closer.

The optics in a lens projects the image onto the sensor. If that sensor is smaller, the image is cropped. Cropping the image makes that distant subject feel even closer.

That crop is why photographers who need to capture close-up images of their subjects sometimes prefer crop sensor cameras. This is even though full-frame cameras usually offer better image quality.

For example, for macro or wildlife photography, you may want to use a crop sensor camera. With one of these, you can reach longer focal lengths.

With Micro Four Thirds, the crop factor is 2x – which means a 300mm lens shoots like a 600mm lens.

That allows photographers to get up much closer with a smaller lens. But unfortunately, this can also mean lower image resolution and lower image quality.

How to Deal With Camera Shake
The camera settings that work with a wide-angle may create motion blur with a telephoto lens. That is because telephoto lenses are more sensitive to camera shake.

The magnification of the lens can exaggerate even the most minor camera movements, thus creating a blur. Telephoto lenses are also heavier, which means your hands are also more prone to shake.

As a general ‘rule’, the denominator on the shutter speed should be at or greater than the focal length when shooting handheld. With a 100mm lens, you should shoot at a minimum of 1/100 of a second. For 200mm, at a minimum of 1/200 of a second.

Heavier lenses may need an even faster speed. To shoot with a telephoto lens and a slower shutter speed, you’ll need a tripod. The rule isn’t true 100% of the time, though. Some stabilized lenses (or lenses attached to a stabilized body) can shoot a bit lower without the shake. This technology utilises gyroscopic sensors and motors to stabilise any movement in the lens elements. This way, it can prevent blur in lenses with longer focal lengths too. A lot of new camera models have in-body stabilisation (IBIS).

What to Know About Telephoto Lens Apertures
Like any lenses, telephotos are more expensive if they come with a wide maximum aperture. But here you cannot avoid buying an expensive one. With telephoto lenses, you usually need to use a fast shutter speed, so you will need a wide aperture. It’s necessary to keep up with the shutter and let enough light in. Also, a lower f-number usually means a better image quality.

Telephoto lenses often are zooms. The cheaper alternatives operate with a variable aperture. You can see it written like 70-300mm f/4-5.6. The more expensive ones have a fixed aperture (usually f/2.8 or f/5.6), and their widest opening likely depends on their focal length.

If you wish to use faster lenses, you can also opt for a prime telephoto lens with a greater f-number and macro capability. Prime alternatives often come with better image quality and macro capability.

How Telephoto Lenses Affect the Background
Sometimes, photographers choose a telephoto lens because of what it can do to the background of the shot. With a telephoto lens, the background appears closer to the subject than with a wide-angle. In fact, the longer the focal length is, the less exaggerated distances seem to be.

Lens compression is a result of standing further from the subject rather than the actual lens optics. Because of lens compression, a telephoto lens can help fill in the background with less empty space. Lens compression will also help the background to appear more blurred. A common misconception is that using a telephoto lens creates a shallow depth of field or creates more background blur.

A telephoto lens does not affect the math for calculating the depth of field. But, the background compression brings that blurry background closer. This gives the appearance of having more blur.

How Telephoto Lenses Affect the Subject
The difference between the background of a photo shot with a wide-angle and one shot with a telephoto is significant. But the subject itself will also have some subtle differences too.

Like the distance between the subject and the background is compressed, other distances in the photo appear to be shorter too. A wide-angle lens will make the eyes, nose, and mouth appear farther apart in a portrait. With a telephoto lens, those facial features appear closer together. This typically creates a more flattering portrait.

The effect is the same for subjects other than portraits too. Remember that a telephoto lens makes distances seem shorter in the image. This is a kind of distortion called pincushion distortion, which is the opposite of barrel distortion. This can happen in zoom lenses and prime lenses too.

Due to the focal lengths, the angle of view of the telephoto lenses is relatively narrow. The lens sees a smaller part of the scene than the camera sensor would be able to detect. So it needs to stretch the image to fill the frame. This can be a bigger problem in cameras using a bigger, full-frame sensor. It’s more visible towards the edges of the image.

To avoid this distortion, you should do profile corrections during post-processing. If you want to create the sense that the objects in the photograph are closer together, use a telephoto. To exaggerate distance in your photography, use a wide-angle.

Conclusion
Telephoto lenses are generally great for situations when you cannot get close enough to your subject. If you want to get a shallow depth of field or avoid barrel distortions, these lenses are also great for you. Experiment with different kinds of photography, and you are going to see what lenses you need. It can happen that you will not need a telephoto lens at all. But now you know what to use telephoto lenses for.

Telephoto lenses can be great for landscapes. Find more best landscape photography practices with our Simply Stunning Landscapes course!