Lens Specifications, Clearly Explained

Introduction

The world of camera lenses is full of technical terms that can seem hard to understand. But most of these concepts are actually quite simple, as long as they’re explained the right way. That’s exactly what we want to try to do. Come along for the journey!

Why and what are millimeters used for?

When we take a look at the specifications of camera lenses the first thing stated is, generally, the focal lenght, expressed in millimeters. After all, what's the most important info we need to know about a lens? Surely, it's whether the lens is wide, to shoot panoramas, or if it's tight, to frame far details.

To make things absolutely clear, a globally accepted scale of values, known as the focal length, has been created. In this page, we want to explain everything in a really simple way, so we’ll use easy examples. Forgive us if they seem a bit basic, but our goal is to be as understandable as possible.

Let's imagine to be in a beach, in front of us there's a beautiful girl who poses for us, on the background there's the sand and the sea. The distance between us and the woman is about two meters, or six and a half feet. If you prefer to imagine a ripped male, there's no problem; we'll stick to the woman, but concentrate on the distance: fixed, two meters, or six and a half feet.

Let's look through the display of our phone or the viewfinder of our camera. If you can see the whole figure, head to toes, we are looking through a wide lens, generally 24 mm. Let's take this as the first example, as it's for sure the one we all are more used to, since it's the standard optic of most of our smartphones.

In theory, now we should start with a long and boring explanation about why it ended up being called 24 mm. It's related to the distance in millimeters from a normal lens to a 35 mm film, but let's do ourselves a favor and skip it. Take it as a fact: 24 mm is a standard wide lens.

Let's go back to our example: the model on the beach, two meters, or six and a half feet, from us, but through a different lens. In this case the girl will appear smaller, apparently farther from us, so much so she doesn't fill the entire frame, but only half.

As the scene stretches to the center, it leaves space for the surrounding area, which before was out of the frame. In this case we are dealing with an ultra-wide-angle; as wider as the lens is, the smaller is the number who name it. An ultra-wide-angle is generally 16 mm or 13 mm.

Now it's pretty logical that increasing the value of the focal length will make the subject appear more and more close and detailed. Going up in focal length, we leave behind the wide lenses reaching the world of normal lenses. The standard normal lens par excellence is 50 mm, but all focal lengths from 35 mm to 70 mm are considered normal.

Going up and up in millimeters, we enter the world of telephoto lenses, which are all the lenses above 70 mm. 200 mm is already a decent telephoto lens, while 600 mm is starting to be a significantly long telephoto lens.

In this game there's no upper limit; also the lenses of the space telescopes for imaging of the farther stars and galaxies can be defined in millimeters, as with the Hubble telescope, which has a focal length of approximately 57,600 mm.

Let’s conclude this chapter with a list of the most common focal lengths in the different categories.

• Fisheye: 8 mm - 12 mm
• Ultra-wide-angle: 12 mm - 14 mm - 16 mm
• Wide-angle: 24 mm - 28 mm
• Normal: 35 mm - 50 mm - 70 mm
• Medium telephoto: 90 mm - 135 mm
• Telephoto: 180 mm - 200 mm - 300 mm
• Super-telephoto: 400 mm - 600 mm - 1000 mm

Prime and Zoom Lenses

In recent days, most of the photos are shot with the phone, but there's a whole world of traditional DSLR lenses that are still a thing. One extremely important thing to know is if the lens is a prime or a zoom.

The main difference is that a prime lens has a fixed focal length that can't change. Generally those are easier lenses, in the sense that they have less mechanism, so the weight is lighter when compared to a zoom lens with the same features. Generally they are better quality lenses, brighter and sharper. In phones, they are the standard.

On the other hand, zoom lenses are one of the most misunderstood terms in photography. Since the same word is often used as a synonym of "magnification," many think that the word "zoom" is the same as "telephoto lens," but the reality is different.

In photography, zoom means the ability to change the focal length smoothly. In other words, it refers to the lens which can be rotated to smoothly change the distance of the subject. In phones, the smooth zoom is digitally simulated, but in the end it doesn’t make much difference.

Considering that in natural speaking the term "zoom" is essentially a synonym of "magnification," it's often used as a simple, although technically incorrect, way to define the focal length range between wide and telephoto lenses. What follows might make traditional photographers cringe a little, but definitions evolve and there’s nothing we can do about it.

In phones 24 mm is de facto the standard, so it's ofter referred to as 1x, as synonim of standard lens. Ultra-wide-angle lenses are often referred to as 0.5x or 0.6x, while bigger ones are used to define telephoto lenses, which are generally called 3x, 5x, or 10x.

The logic is really easy to understand now that we have clear how millimeters define the focal length. If we assume 24 mm to be the standard 1x, a lower number such as 0.6x requires calculating 24x0.6=14 mm, which is very wide, while a higher number, such as 5x, requires calculating 24x5=115 mm, which is a decent telephoto lens.

This logic existed before the phones; it appeared with compact cameras Bridge, which often offered extreme zooms. Smartphones are also beginning to offer cameras with very high zoom levels, thanks to the use of periscope telephoto lenses built directly into the body.

Obviously these are commercial terms, often rounded up, and are not the same as specifications, but those are an easy way to define, approximately, the effective magnification of a lens.

Image Stabilization

When using extreme telephoto lenses, it becomes difficult to keep the subject steady when shooting handheld, and the frame will appear very shaky. To reduce this problem, image stabilization has been invented. It's an electronic system applied to the lens or the sensor designed to counteract the vibrations of the hand as far as possible.

A stabilizer can reduce the risk of blurry photos by up to four times, at the cost of a slight loss of sharpness. The results depend a lot on the lens quality and the type of shot, but the important thing is that it helps us a lot to avoid blur in low light or when shooting with a telephoto lens.

There are several names used for stabilization systems; the most well-known is OIS, which is the standard in phones. The most famous brands use VR for Nikon, IS for Canon, OSS for Sony, VC for Tamron, and OS for Sigma.

Aperture

When buying a new lens, focal length is important, but it is not the only parameter to consider. The brightness of the lens is also extremely important, even more than its focal length.

A lens's brightness is determined by how much light the lens is able to capture and is defined by the letter "f" followed by a "/" and a number. Just like focal length, aperture values follow a standardized scale that defines exactly how bright a lens is. Here are the main aperture values:

• f/1.2: One of the lowest possible values. It's a feature of very expensive and professional lenses, and it's extremely bright.
• f/1.4: The same considerations as above apply here.
• f/1.6: Typical of high quality photographic phones.
• f/2: An excellent value for a prime lens.
• f/2.8: A perfectly acceptable value for a prime lens, excellent on a zoom lens.
• f/4: A more than respectable value for a zoom lens.
• f/5.6: The standard value for mid- to low-quality zoom lenses.
• f/8: Not particularly interesting; some very powerful but compact telephoto lenses use it.

This topic has been covered only briefly here because we have already written a detailed article about aperture and depth of field. You can read it by clicking below:

Aperture of the f-stop in photography How the aperture and f-number affects the depth of field and the shutter speed. Reading time: 7 min.

Autofocus and Ultrasonic Motors

Manufacturers always have a selection of lenses in their catalog that are superior to the others. To distinguish these premium lenses, a specific label is used: L for Canon, ED for Nikon, GM for Sony, EX for Sigma, and SP for Tamron. They are often recognizable by a distinctive color, such as white, or by a logo, or a red or gold ring. These lenses, in addition to higher build quality, often include advanced features.

One feature of high-quality and high-priced lenses is the autofocus with ultrasonic motor. It is a better type of motor, which is much faster and quieter. It is defined with USM on Canon lenses, AF-S on Nikon, DDSSM on Sony, HSM on Sigma, and USD on Tamron.

Lens Names

Now that we know all the possible features of a lens, let's look at some commercial names to review all the concepts.

Canon 24 mm f/1.4 L USM II: Made by Canon, this is a 24 mm prime lens. We’re in wide-angle territory, but nothing exaggerated. Extremely bright, thanks to its f/1.4 aperture, it belongs to the premium series indicated by the letter L. It features a ultrasonic autofocus, the best, defined by USM. The Roman numeral II indicates that it is a second version, an older project updated with more advanced technologies.

Nikon 70-200 mm f/2.8 VR: In this case, the manufacturer is Nikon: Since the focal length is defined by two numbers it is a zoom lens ranging from 70 mm to 200 mm. It’s a telephoto lens in every respect, since it starts at 70 mm, which is already considered a light telephoto. It's an excellent lens because it maintains a constant f/2.8 aperture throughout the entire zoom range. It's a stabilized lens, as indicated by the label VR.

Sigma 18-200 mm f/3.5-6.3 DC OS HSM: Here the lens is made by Sigma, and it's an extreme zoom ranging from 18 mm to 200 mm. Its brightness is mediocre, which is typical for this type of lens. At the wide-angle end, it's f/3.5, and at the telephoto end, it reaches f/5.6. The label DC means it works only on APS-C cameras, OS indicates that it is stabilized, and HSM means that the autofocus uses an ultrasonic motor.

Tamron SP AF 90 mm f/2.8 Di MACRO 1:1: Made by Tamron, SP stands for super premium, and AF means autofocus. It's a 90 mm prime lens with a reasonably bright f/2.8 aperture. The label Di indicates that it is designed specifically for digital sensors, and MACRO 1:1 means it is a lens specific for tiny details and allows you to get really close to the subject.

Conclusion

We hope you liked this page about all you need to know about camera lenses. Before saying goodbye, we would suggest you read our home page, with all the articles we wrote about Cortina d'Ampezzo.

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