Photography 101: Focal Lengths

By F.M. Kearney

In last month’s Photography 101 article, I discussed what I consider to be one of the most fundamental basics of photography: apertures and shutter speeds. Following closely behind in terms of importance are focal lengths. Simply put, the focal length describes the angle of view of a lens, as compared to natural eyesight. It’s a measurement (expressed in millimeters) of how much of a scene it captures. A long focal length lens, such as a 200mm lens, captures a narrow angle of view, or an enlarged view of the subject. These types of lenses are known as telephoto lenses. A short focal length lens, such as a 28mm lens, captures a much wider angle of view, making the subject appear smaller. As their angle of view implies, these types of lenses are known as wide angle lenses. Lenses that encompass multiple focal lengths are known as zoom lenses. They are easily identifiable with ranges such as 12-24mm, 24-70mm or 100-300mm. A variety of focal lengths can be achieved simply turning or sliding a ring on the lens.

Zooming In

I shot the photos above on the Bethesda Terrace, which overlooks the famous Bethesda Fountain in New York’s Central Park – one of its most popular attractions. Vastly different views can be created by using different focal lengths. Whether it’s a fisheye view at 16mm, a “normal” view at 50mm, or a telephoto view at 200mm, a variety of compositions can be captured without changing your physical location.

A fisheye lens is an ultra-wide-angle lens that takes in an extremely wide view and creates a barrel-like distortion. It’s not a lens you would want to use for everyday photography, but it is fun to play around with and to create some really unusual perspectives. There are, of course, “regular” ultra-wide-angle lenses that don’t create this distortion. A 50mm lens is referred to as a “normal” lens because it doesn’t create any distortions, and it’s considered to reflect normal eyesight. However, some photographers consider a 24mm or 28mm focal length to be a more accurate representation of normal eyesight – especially when you take into consideration your peripheral vision.

Zooms vs. Primes

So, the question now becomes whether you want the convenience of having multiple focal lengths in one zoom lens, OR, through a series of individual focal length lenses, referred to as prime lenses. I actually used three lenses to take these photos… a prime 16mm fisheye, a 24-70mm zoom and a 70-200mm zoom. Without the zoom lenses, I would have needed six individual prime lenses to capture all of these focal lengths. Years ago, prime lenses were considered the better choice because their resolution was generally superior to that of most zooms. But, the resolution of today’s modern zooms is equal (or better) to that of primes. With the added benefit of having several focal lengths in one lens, you might think the choice would be clear. But there are pros and cons between zooms and primes to take into consideration.

While it is convenient to replace several lenses with one, zoom lenses are much bigger and heavier than primes. Unless you’re in the habit of using a tripod all the time, having to hand-hold a camera with a zoom lens attached can become quite tiresome, and even painful, over long periods of time. Although I have a 24-70mm zoom, I still carry a 28mm prime for times when it’s impractical to use a tripod and I have to hand-hold the camera. The lighter weight of this much smaller lens makes life much easier. On the other hand, zoom lenses eliminate the need to constantly change lenses – reducing the risk of dust landing on your sensor.

The maximum aperture of prime lenses is generally wider than that of most zooms. Unless you’re willing and/or able to spend thousands of dollars on a pro-level zoom, the maximum aperture of your zoom will only be around f/5.6. This won’t affect the quality of your images, but you won’t be able to produce those super-soft backgrounds, created by apertures of f/2.8 or wider, that really make your subject stand out.

So, in the end, it ultimately comes down to your own personal preference, finance and style of shooting. Whether you want to lighten your load with a single prime lens, or enjoy the flexibility of a zoom, the choice is yours.

Controlling Your Perspective

Many beginning photographers tend to get caught up in the fun of zooming in and out through space. But it might surprise you to know that I rarely use my zoom lenses for this purpose. In many cases, I can just walk right up to my subjects and shoot them at a normal or wide-angle focal length. Oftentimes, the main reason I’ll use a zoom lens is because I want to get a certain perspective – a more “compressed” perspective.

The photo above is a wide-angle view of Oak Bridge in Central Park. Shot at 24mm, it appears to be much longer than its actual 60 feet. But when shot at 100mm (below) it’s compressed and appears to be much shorter. I’ll often use a zoom lens to create this type of spatial compression, where the foreground is brought much closer to the background.

Compression is also a good way to emphasize the symmetry of a repeating pattern, like a line of trees or flowers, or as in the case of the photo below, a row of bridge posts.

When shot at 170mm, the bridge posts appear closely stacked together. However, when photographed at 24mm (below), you can clearly see that there’s a considerable distance between them. In order to get these different looks, you have to change your camera-to-subject distance. When I shot the photo of the entire bridge at 24mm, I was less than a foot away from the two stanchions in the front. To get the compressed look at 100mm, I had to back up a good 50 or 60 feet – practically double the length of the bridge itself. Although not quite as drastic, a considerable change in camera-to-subject distance was necessary for the bridge posts photos.

Disappearing Act

I’ve shown how a long focal length can enlarge a subject and compress space, but there’s another lesser known (but useful) thing it can do as well. The photo above is a typical park scene. There’s nothing unusual about it except for one thing… where I was standing when I shot it.

As you can see from the photo above, I was standing behind a fence. In case you were wondering, no, I did not remove it in Photoshop. The fence is still there, but when shot at f/2.8, I eliminated all my depth of field, thus, rendering it so out of focus that it’s virtually invisible. At f/22, however, I’m at maximum depth of field and the fence becomes glaringly obvious. (For a more detailed explanation about depth of field, please refer to my last month’s article, “Photography 101: Apertures and Shutter Speeds.” This effect is only possible when the lens set is to f/2.8 or wider, and most importantly, when using a focal length of around 200mm or longer. At 70mm (below), the fence is still visible, even at f/2.8.

This technique is not something I would recommend doing on a regular basis. Sometimes, depending on a variety of factors, traces of the fence (or whatever type of barrier it may be) may still be visible, even at 200mm and f/2/8. Therefore, if you’re able to step in front of the barrier safely and legally, you should absolutely do so. But, if you’re in a bind and have no other choice, this little trick will at least give you the option of getting a photo that may be slightly imperfect, as opposed to not getting any photo at all. Lastly, if you do try this technique, it’s best to do it on manual focus, because auto-focus will undoubtedly focus on the barrier and not the subject.

Experimenting with different focal lengths can really improve your photography. You can get the precise composition you want at a perspective that best expresses your vision.

F.M. Kearney began his career as a photojournalist for a variety of local New York City newspapers. It was an exciting profession, which allowed him to cover everything from famous celebrities to ride-alongs with NYPD and FDNY. He now specializes in nature and urban landscapes. To view more of his work, visit www.starlitecollection.com. He can be contacted at starcollec@aol.com, or followed on Facebook (@fmkearneyphotos) and/or Twitter (@fmkearneyphoto).