When should you use a 20mm lens? When an 85mm? And what about the classic 50? The difference among focal lengths is not just a matter of how much stuff you can get in the frame. If it was just about that, it would be easy to choose one or another.

Do you have in front of you a large vista? Than a 12mm is fantastic. Need to take a picture of a distant mountain peak? Swap that 12mm for a 300 and you’ll be fine. Do this, and you will be shooting pictures as boring as of those shot by 90% of people.

I am going to quote Jim Simmons, a fellow photographer, who gave in my opinion the best definition of the character of each focal length:

“Speaking in full frame terms, I feel that we ‘sense’ in 21mm, we ‘perceive’ in 28mm, we ‘see’ in 35–40mm, we ‘look at’ in 50mm, and we ‘examine’ in 75–90mm.”

Now let’s go deeper to understand what he meant with that.

I’ve always had a hard time deciding which lens to choose, especially between similar focal lengths like 35mm and 50. I like them both very much and I can get good pictures with either, but which one to choose? At first I tended to use much more the 50mm outside, and the 35mm inside.

But still this was not the answer. And then I finally noticed something that changed my lens game forever, and I hope will do the same for you.

You pick up pretty soon, even as a beginner, that pictures shot with telephoto lenses appear more detached, while if you are using a wide angle the resulting photograph will look more like you were in the midst of the action. So lens choice is first of all a way to convey mood, not just a way of capturing the entirety of a scene.

Sure, composition has its place, but it is the other way around: you will choose a lens and then compose, not vice versa. Beside, lens choice also affects your viewer freedom.

As a general rule, the longer you go up in focal lengths, the less freedom your viewer will have to explore as he wishes your picture.

A picture shot at 12mm is like a wild forest, with almost no paths, where the viewer can go as he pleases. An image shot at 300mm will be like one of those guided wooden paths that let you visit a national park without even stepping on the grass. Both can be nice experiences, but won’t appeal to the same people.

But there is much more to this.

A focal length has also a deep connection with the way we perceive reality. So let’s look at the real difference between the different focal lengths and what should guide our choice.

21mm and below

21mm and wider focal lengths look at the world in the way we tend to absorb a scene.

You are on a beach, and you take everything in: the sand, the glimmering of seawater, the beach umbrellas and so on and so forth. Your attention will probably be focused on nothing in particular, though. Wider focal lengths do not discriminate easily among different elements. The larger you go, the more important composition becomes. It will be the photographer’s responsibility to guide the viewer gaze were he wants.

Sometimes there will be no section more important than the other, and in that case the photographer will offer the viewer the freedom to explore as he pleases the scene he captured. This is not an easy feat, and in general the larger the section of a scene you capture, the more difficult will become to make a picture that is not boring.

24 & 28mm

24 and 28mm are the way we perceive the world around us. Meaning that it is how we generally focus on a scene, giving attention to some bits but also scanning all around the actual action taking place.

You see the guy riding the camel, but the tents in the background and the palm tree on the left as well, even if your attention is focused on the rider. Not for anything, 24 and 28mm have always been a favorite among photojournalists.

Composing becomes way easier in comparison with wider lenses, because you are forced to make a choice and cut out just a particular section of a scene, thus focusing the attention of the viewer on a specific action or section. Capturing a moment becomes much easier as well, because you only have to focus your attention on a specific direction waiting for the right moment to click the shutter.

35 & 40mm

And now one of my favorites, the 35mm focal length and its half-sibling, the 40mm.

This is how you tend to see a scene, meaning that a 35mm lens tends to capture the entire “cone of attention” of our gaze. Another long time favorite focal length of many a photojournalist, a 35mm lens puts your subject or the action in context. Any picture you take won’t be just a photo of a person, but of a person in their environment.

This is a fantastic focal length for shooting single images that contain an entire story.

Sure, a wider lens like a 24mm can do the same, but it often brings that little bit of distortion that let us brain know we are looking at a picture, and not at a slice of reality itself.

With 35mm you can start as well shooting portraits. Won’t be classical portraits: facial features will be distorted, the nose especially will be exaggerated. But on the other hand you will gain a sense of intimacy with your subject, a presence, that a longer focal length will lack.

An amazing feature that any 35mm (or equivalent) has is that you can quickly estimate your composition without the need to bring the camera to your eye. The distance between you and your designated subject will be the width of your picture, meaning how much of the scene you will be able to capture. So, to go back to our camel rider example from before: if you are standing 2 meters away from the camel, the horizontal amount of the scene that you will be able to capture will be 2 meters as well. If you are standing 5 meters away, the width of the scene that will be in your picture will be 5 meters and so on.

This is another reason why 35mm is an all time favorite among photojournalists. They can quickly compose without the need of looking through the viewfinder, just briefly rising the camera only for the time needed to take the shot.

50 & 60mm

How do you choose between 35mm and 50mm? Well, in 50mm we are no longer just gazing at our subject, but we are really looking at him, concentrating our attention. It is the equivalent of moving closer to something or someone to better examine a detail. You use a 50mm when you want to really show something to your viewers, pointing their attention in a specific direction. For our purpose, a 60mm is not much different, just a touch too tight (for my taste) if used inside, and generally way less fast than your typical 50 (60mm are usually macro lenses, with an f/2.8 maximum aperture).

50mm is possibly my favorite focal length to shoot portraits with, because while still retaining that sense of intimacy that a 35mm has, it will distort less any facial feature.

In the last years 50mm has become a favorite lens to practice challenges like “one lens one year’ and such. Well… when I started taking pictures I began using my dad’s camera, that came — like it was pretty standard at the time — with a 50mm lens. And I’ve used that same lens (that I still use, by the way) and only that 50mm lens for 6 or 7 years straight.

After a bit you begin to get pretty familiar with what the framing will be, and you start composing without even thinking.

75 to 105mm

Lenses from 75mm to 105mm are essentially magnifying glasses. Not just because they make every detail bigger, but because we resort to them when we need to examine a scene or a subject.

The tend also to flatten the perspective (due to the fact that you will no longer need to get closer to your main subject), and this makes them excellent when you want to emphasize the 2d, graphical aspect of a scene. For the same reason these are lenses that will not add any distortion to a face, beside making it look a bit flatter, so they are often preferred by classical portrait and fashion photographers.

In pretty much every system and format I ever had, my most used combination has ever been either a 24mm plus an 85mm for versatility, or a 35mm plus a 50mm for the quality of the results, in terms of how much I liked them.

Over 105mm

Lenses over 105mm are, in my opinion, special use lenses only.

You tend to use them for something really specific, for example:

  • a fashion photographer that wants a 300mm f/2.8 for maximum compression and to blow the background to bits;
  • a landscape shooter who wants to compress the composition in order to give his images a more graphical aspect.

Or because, quite simply, you cannot get close enough to your subject to fill the frame as much as you wish, think bird or sport photographers.

What lens should you use?

So, what focal length should you use? Like many things in life: it depends.

Especially if you are a total beginner, try to look at pictures shot with different focal lengths, just to understand if you like or not the results, preferably before shelling out a lot of money for a new toy.

Use Flickr, Instagram etc. and blind-test yourself collecting a series of images that you like the most, at least a hundred or so. Then check the kind of lens they had been shot with.

In the end, I bet you will discover that 90 plus per cent of your favorite pictures have been shot with just one or two lenses. Buy one — or both — of these, assuming you do not already own them, and have fun!



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