When to use a telephoto lens (and its effects)

You might not know it, but anyone with a camera has, without a doubt, used a telephoto lens at some point—even without realising it.

It's not just the professional cameras with telephoto lenses—the camera on your Smartphone also has one. You may have heard it more commonly called the ‘zoom’.

In a nutshell, a telephoto lens brings everything closer. However, there is far more to it than pure magnification.

We've outlined key tips for when and how to use a telephoto lens, as well as its advantages and the effects it produces.

 

What is a telephoto lens?

Before we jump into using a telephoto lens, let's consider what one is.

As previously mentioned, you've likely heard the term ‘zoom lens’ rather than ‘telephoto lens’, but what is the difference? Well, there isn’t one.

A zoom lens is simply a telephoto lens that can be adjusted for different magnification strengths. Telephoto refers to anything magnified beyond the standard field of view equal to the human eye.

To fully understand this, first, we need to delve into the realm of focal lengths.

While most compact and bridge cameras will quote you magnifications by a times factor, such as 4 x zoom, Single-lens Reflex (SLR), and modern mirrorless cameras will come with lenses that quote a focal length in millimetres. The focal length is the distance between the main lens glass and the focal plane (i.e. the film or sensor).

 

What focal length is telephoto?

The focal length that equates to the naked eye will vary according to the film or sensor size relative to the lens size. However, for a 35mm film SLR camera and full-frame digital single-lens reflex camera (DSLR), this focal length is 50mm.

Anything above 50mm is considered to be magnifying the scene and thus becomes a telephoto lens. Conversely, anything below 50mm is considered a wide angle because it stretches the scene to a wider view than the naked eye.

As your focal length gets longer, the field of view narrows, and thus it begins to crop out the wider part of your scene, only allowing part of it to pass through the lens and onto your sensor. So less of the scene falls onto the sensor and is cropped out.

 

The crop factor

Many DSLRs are not full-frame and have what is known as a crop factor.

A cropped sensor is smaller and therefore doesn't capture the whole scene that passes through the lens. Essentially, the image is then cropped by a factor of, for example, 1.5, depending on the sensor size. It is like cropping some of the image off in your post-processing software. So, for example, on a 1.5 crop sensor, a 50mm focal length becomes 75mm, thus turning your standard field of view into a telephoto one.

 

It’s all an illusion

It's all, in fact, just an illusion.

The narrow field of view magnifies your subject and brings it closer, but in reality, it just crops out the surrounding parts, so you only see the subject. Effectively, it isolates a subject, making it the only thing you record, so it will appear big in your picture.

You may have also heard the term ‘digital zoom’. This crops the digital image recorded on the sensor, which also crops out the pixels and results in a loss of quality.

However, because an optical zoom or telephoto narrows the field of view, the whole scene within that field is recorded using the full resolution of the sensor and thus results in a higher-quality image.

 

Telephoto lens effects

Apart from the obvious effect of magnifying a subject, telephoto lenses have many other effects and reasons for using one.

 

Narrower depth of field

Depth of field is the distance in front of and behind your point of focus. Anything inside this depth of field is sharp, and anything outside is blurry.

The smaller your aperture is, the larger the depth of field (so the background is sharper). The larger your aperture is, the smaller the depth of field (so the background is more blurry).

Aperture is measured in f-stops. F16 is small, and F5.6 is large. However, the physical sizes are not fixed—they depend on the focal length.

The physical size of the hole is calculated by dividing the focal length by the f-stop. For example, f16 at 50mm - 50/16 = 3.12mm. So, the physical size of an f16 aperture at 50mm is 3.12mm.

However, increase that focal length to 100mm, then 100/16 = 6.25mm. A larger hole will result in a shorter depth of field—meaning the background of a photo taken at 100mm focal length will be more blurry than one taken at 50mm.

 

Bringing background objects closer to the foreground

Another useful telephoto lens effect is compressing the scene to give the illusion of the foreground, making background objects much larger and closer to each other.

By cutting out the wider parts of a scene, everything seems much larger. Moving back and focussing on something from further away rather than up close changes the whole dynamic of the scene.

The opposite is true for a wide angle.

Using a wide-angle lens and focusing on something close to you makes foreground objects much larger and background objects smaller and seemingly further away.

35mm focal length – in front of the long grass

105mm focal length – standing further back

In these two photos, you can see the difference.

The first image was shot at 35mm while standing in front of the tall grass. I moved back across the road for the second image and zoomed in to 105mm.

You can see in the image shot with the telephoto how the church appears much closer to the grass and also larger in the photo overall. In the first, the wide-angle and closer position to the foreground has shrunk the church in the scene, and now it appears much further away.

 

 

When to use a telephoto lens

So now we have looked at telephoto lens effects and how it all works, let's look at when to use a telephoto lens.

 

Portraits of people or animals

The most obvious reason for this is to ensure you're not too close to the subject.

You don't want to spook animals, of course, and for people, it can be quite daunting to have a photographer in their faces. Moving further away makes a person feel less uncomfortable, resulting in a better photo. Naturally, we can then use the telephoto to go in close and frame our subject fully in the image.

When shooting portraits of people or animals, we also want to blur the background in most cases to make the subject stand out. This can be especially useful when busy, distracting elements are behind it.

Blurring that background can be done by opening the aperture to reduce the depth of the field. However, sometimes it is not enough.

Setting the lens to its widest aperture—for example, f4—can be the limit. But what if you want more?

Moving physically closer to blur the background is an option, but as mentioned, this would make our subject more uneasy. Therefore, it is better to move back and use a telephoto. The longer focal length will increase the physical size of our widest aperture and result in blurrier background.

 

260mm – F7.1 – bushes behind

                       

     

400mm – F7.1 – grass behind

 

Wildlife Photography

Super telephoto ranges can photograph wildlife—particularly birds and wildfowl that are easily spooked and must be photographed from within a hide. Additionally, we can use it to photograph more dangerous wild animals, as you certainly don’t want to get close to them.

 

Photographing Mountains

They say you can’t move a mountain, but a telephoto lens can.

Telephoto lenses are perfect for getting close to mountains, especially mountain peaks. They are ideal for picking out the detail.

In most cases, you would need a good-quality lens to ensure clear and accurate details. If shooting handheld, be sure to have a fast enough shutter speed, especially if using a big, heavy lens.

A tripod is needed in most cases to ensure a nice sharp image. Plus, mountains are often best photographed at sunrise or sunset and with dramatic clouds swirling around, so you might also want to use a long exposure.

 

Subjects against mountains (sense of scale)

A telephoto lens can be used to emphasise scale.

If you stand in front of something like a church or a castle with a mountain behind, then the church will seem bigger than the mountain. However, if you move further back and zoom in, it all looks different.

Standing back and zooming in lets you see the mountain background much larger against the smaller building.

 

Photographing the sunrise or sunset

A telephoto lens is great for getting close to the sun as it rises or sets.

Using the super telephoto to zoom, you can get right up to the sun on the horizon as it appears or disappears, especially over the ocean.

It is also great for capturing a sunset over mountain peaks or when it rises behind specific landmarks.

Including some foreground, features is a plus—and that is where the zoom is useful. You can vary our focal length to get one shot right up close, then pull back to include something else in the scene, such as interesting clouds.

 

Photographing the moon

You might use a telephoto lens to photograph the moon up close. Still, it is also useful for photographing the moon as part of the landscape as it rises or sets, just like the sun or behind landmarks.

 

Making the best of a bad sunrise

We all love those amazing flaming sunrises when the whole sky lights up. However, it doesn’t always turn out that way. All is not always lost, however. Often there is some colour on the horizon, particularly where the sun has gone down. A telephoto lens can be used here to isolate the colourful part of the scene itself.

 

What kind of telephoto lens do you need?

There are, of course, many more uses for a telephoto lens. So, when you consider adding one to your kit, consider what you will use it for.

There are many to choose from, but like with any lens, quality is important. Remember that the lens is the first entry point for your image, so having a cheap budget lens on a high-quality camera body will cheapen your camera.

Consider what you will use it for and, of course, what your budget is. A higher quality lens would be necessary for distant landscapes to ensure sharpness where there is a lot of detail. However, for people and portraits, there is less small detail, so that you could get away with a lower budget lens.

Also, consider what you will use the photos for. You don't need high quality if you are a hobbyist or part-time pro. But quality and sharpness are paramount if you are a serious professional and want to sell your images, especially as large prints.

So, get out there and embrace the power of the telephoto lens.

 

About the author:

Ian Middleton is a travel and landscape photographer and writer. He is the author of several books, including a practical guide to photography. His photography has been used in numerous publications worldwide and is sold as high-quality wall art online.

Visit his website for more info.

 

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