Comprehensive guide to choosing your photographic lens: exploring different lenses

Explore this comprehensive guide to choosing the perfect photographic lens. Dive into various lens types to find the right fit for your camera.

Author: Marco Crupi

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This article is a segment of the Digital Photography Course. Click here to return to the main course overview.

To achieve good image quality in our photos, it’s not just about the camera body; the photographic lens is equally important for producing sharp and detailed shots.

There isn’t a perfect lens for every situation. As I mentioned in the previous article about camera types, it’s all about trade-offs. Therefore, when choosing a lens, one must weigh the pros and cons of each, keeping in mind our budget.

There are numerous lenses on the market across various price ranges and types. This photography course lesson will help you select a photographic lens that meets your needs.

THE LENS HOOD

Along with the lens, we are provided with a lens hood. But what is its purpose?

  • To counteract stray light, thus preventing a loss of sharpness, or what’s known as flare.
  • To protect the front element of the lens.
  • Adding any type of filters in front of the lens increases the chances of unwanted refractions. In such cases, using the lens hood is highly recommended.
Hood mounted on lens

FOCAL LENGTH AND FIELD OF VIEW

The focal length of a lens is defined as the distance between the lens’s optical center and the camera’s image sensor and is measured in millimeters.

Put simply, our camera’s zoom is based on changes in focal length: a shorter focal length allows us to see a wider portion of a scene, while a longer focal length lets us get closer to subjects, zooming in on them. In basic terms, a smaller focal length (e.g., 18mm) is like stepping back from the action, capturing more elements in the scene, great for landscapes or group photos. Conversely, a longer focal length (e.g., 200mm) is like getting closer to the action, allowing the isolation of subjects or details, ideal for portraits or wildlife photography.

Focal length doesn’t just alter the apparent “distance” from subjects, but also the perception of depth and proportions in a photo. For instance, a wide-angle lens can exaggerate the distance between foreground objects and those in the background, creating a depth effect, while a telephoto lens can compress the apparent distance between objects, making them seem closer together than they actually are. I delve deeper into this topic in the section on perspective in photography.

On this lens, the details provided on the front tell us: the maximum aperture at the shortest focal length is f/4, while at the longer end it's f/5.6, the focal length ranges from 100mm to 300mm, and the filter mount diameter is 67mm.

The focal length of a lens is typically stated on the front of the lens, along with the symbol for the filter mount diameter (useful for filters, which I’ll elaborate on in a specialized article) and the maximum aperture values.

Based on the focal length, we can categorize three main types of lenses:

  • Wide-angle: have a focal length less than 35mm.
  • Standard: have a focal length between 35mm and 50mm.
  • Telephoto: have a focal length greater than 50mm.

A specific focal length corresponds to a specific field of view, i.e., the portion of the scene we can see through the viewfinder or camera display. In reality, this parameter also depends on the camera sensor, but that’s a topic I’ll address in another article. Here, we’ll consider the field of view of a lens mounted on a full-frame camera.

The image above helps us understand how as the focal length increases, the field of view narrows; conversely, the more wide-angle the focal lengths are, the broader the field of view.

LENS BRIGHTNESS: THE APERTURE

The brightness of a lens is determined by the maximum aperture of its diaphragm. The brighter the lens, the easier it will be for us to shoot in low light environments. The diaphragm is a circular or polygonal mechanism made up of thin metal blades that, when sliding over one another, create a variation in the diameter of the opening. This regulates the amount of light passing through the lens, with the light eventually reaching the sensor.

Modern lenses typically use an adjustable type of diaphragm known as the “iris diaphragm“.

The range between different aperture values is commonly referred to as a “stop”. The “f” numbers are calculated and arranged in such a way that closing the diaphragm by 1 stop halves the amount of light, closing it by 2 stops reduces the light by 1/4, closing it by 3 stops by 1/8, and so on.

Lenses with aperture values equal to or lower than f/2.8 are considered bright lenses. As can be seen from the image above, the lower the number after “f/”, the more open the aperture will be. Conversely, the higher the number, the more closed the aperture will be.

The aperture also affects depth of field, but I’ll cover that topic in another article.

STANDARD LENS

In photography, a standard lens reproduces a field of view that appears “natural” to a human observer. In contrast, the compression and expansion of the depth of field with shorter or longer focal lengths introduce significant and sometimes disturbing distortions.

Conventionally, lenses ranging from 35mm to 50mm are considered standard. However, it’s worth noting that photographic technology, for obvious reasons, employs different technical solutions than the human eye for capturing images. Consider that the human eye has a concave retina rather than a flat sensor. Moreover, human vision is binocular, meaning it uses two “lenses” instead of one. Additionally, the “post-processing” by the brain is very different from the processing of a photograph.

Thus, there isn’t a clear correlation between human vision and camera lenses. Photography books and online articles often simply argue that the 50mm “resembles the field of view and magnification of human vision” or that “the perspective at 50mm is more accurate, and we are more comfortable with an image captured with this type of lens.” Referring to a similar field of view as that of the human eye is evidently a mistake, as our extended field of vision averages around 95° horizontally and 80° vertically, while the field of view for the 50mm is only 46°.

WIDE-ANGLE LENS

Canon Fisheye – Photo by Dirk-Jan Kraan

A wide-angle lens has a focal length shorter than that of a standard lens, thus less than 35mm. This type of lens is useful for capturing broad portions of a scene, making it a popular choice for landscape, architectural, and interior photography. These are genres where a photographer might not be able to distance themselves from the scene to photograph it, and without a wide-angle, they wouldn’t be able to capture it in its entirety. Wide-angle lenses are not recommended for portrait photography as getting too close to the subject can distort their face.

Wide-angle lenses can also emphasize the size difference or distance between foreground objects and the background. With this kind of lens, close objects appear much larger, while distant objects seem smaller and further away than they actually are.

Worthy of separate mention are ultrawide lenses, termed “fisheye” lenses. These lenses have focal lengths of 16mm or shorter and a field of view of no less than 180°.

Example of a Fisheye photo taken of the STS-131 and Expedition 23 crew members in the International Space Station.

Fisheye photo example

TELEPHOTO LENS

A telephoto lens allows you to photograph a distant subject or magnify the subject within our image. Even though it enables us to capture elements far from us, this doesn’t mean the effect is the same as approaching the subject. This is due to the different planes within the frame appearing closer to each other (a phenomenon known as compression) compared to reality and how they would appear when photographed up close with a wide-angle or standard lens.

A telephoto lens has a longer focal length compared to standard lenses, so any lens with a focal length greater than 50mm is considered a telephoto. Telephoto lenses can be divided into three subcategories:

  • Medium Telephoto: lenses with focal lengths ranging between 50mm and 100mm.
  • Telephoto: lenses with focal lengths between 100mm and 300mm.
  • Super Telephoto: lenses with focal lengths greater than 300mm.

In portrait photography, medium telephoto lenses are typically used, with the conventionally suitable focal lengths for this genre being between 70mm and 85mm. In sports photography, telephoto focal lengths of 300mm and above are used.

In the photo above, the Strait of Messina was captured using a wide-angle lens. You can spot in the distance, highlighted in red, the Calabrian Pylon and Scilla. Immediately after taking this photograph, I switched to a telephoto lens, achieving the results shown below.

The Calabrian Pylon photographed from Messina with a telephoto lens – Focal length used: 100mm on micro 4/3, equivalent to 200mm on 35mm.

The Calabrian Pylon was about 3km away from me, but thanks to the telephoto lens, I can see it as if I were just a few steps away.

Scilla photographed from Messina – Focal length used: 180mm on micro 4/3, equivalent to 360mm on 35mm.

I took this photo from a distance of 5.5km, yet due to the compression effect of the telephoto lens, viewers get the impression that they could cross that narrow strip of sea in just a few strokes.

PERSPECTIVE RENDITION

Many are convinced that as the focal length changes, so does the perspective. The perspective doesn’t change if the viewpoint and the captured subject remain fixed; it only changes if we move from the shooting point. However, the perspective rendition does change: wide-angle lenses tend to emphasize vanishing points and enhance the sensation of space and depth, while telephoto lenses flatten the perspective, making subjects appear much closer to each other.

Therefore, depending on the lens used, the sense of perspective in photos varies. The relationship between objects, or the distance between them, changes depending on the focal length used.

Photo taken with a 105mm focal length on APSC.

Photo taken with an 18mm focal length on APSC.

The chess pawns are equally spaced from each other in both photos (3 squares apart). If we photograph them with a telephoto lens, they seem close, while with a wide-angle lens, they appear separated by a greater distance.

IMAGE-STABILIZED LENS

Highlighted in red is the switch that allows you to activate and deactivate the lens stabilizer.

The image stabilizer can be found either on the lens or on the sensor. Stabilization on the lens uses a system of movable lenses, electronically controlled to compensate for hand vibrations with an identical but opposite movement, thus neutralizing them. Image sensor stabilization works in a similar way, but it physically shifts the sensor itself to counteract the movement.

At first glance, an image-stabilized lens always seems like the better choice, and indeed it is. The only downside is that stabilization increases the lens’s price, so if we’re on a tight budget, we might consider buying a non-stabilized lens.

Each manufacturer has its own acronym to denote its stabilization system:

  • Nikon: VR
  • Canon: IS
  • Panasonic: O.I.S.
  • Tamron: VC
  • Sigma: OS

When using the camera on a tripod, it’s advisable to deactivate the optical stabilization system, as this can trigger what’s called a “feedback loop.” In this scenario, the camera’s stabilization system detects its own vibrations and starts moving, causing micro-movements in our image. Modern cameras should prevent this from happening due to their auto-off stabilization system, but for safety, it’s better to manually deactivate it.

Many believe that stabilization reduces a lens’s sharpness, but this isn’t the case. Although stabilized lenses have a more complex optical design, thanks to advancing technology, they prove to be even sharper than their non-stabilized counterparts.

Generally, stabilization is deemed necessary only for telephoto lenses because the higher the focal length, the more hand vibrations can cause blurriness. However, this isn’t entirely accurate, as having a stabilized wide-angle lens allows us to shoot handheld at very slow shutter speeds. For instance, with my camera (a Panasonic Lumix G9), I can photograph landscapes and architectural works at night using shutter speeds between 1/10s and 1/20s without any micro-movements, something unthinkable without a tripod before the introduction of this technology.

PRIME LENSES VS ZOOM LENSES

Prime lenses have a fixed focal length, which means that to get a closer or more distant shot of the subject, we must physically move ourselves.

In contrast, zoom lenses are designed to allow the use of multiple focal lengths.

Prime lenses have superior quality compared to zoom lenses. This is because the greater the focal range, the more optical compromises must be accepted. For instance, an 18-200mm lens has a significant focal range but will require many more optical compromises than an 18-55mm or a 55-200mm lens. The quality provided by the two separate lenses will be higher than that of a single lens covering the same focal lengths. It’s a matter of choices: do you prefer versatility or quality? The answer depends on the results you want to achieve.

On the now-closed forum of fotografare.com, a user named Attilio gave a fitting example during a discussion:

Building a car that reaches 200km/h isn’t difficult; any modest vehicle with a peppy engine can easily achieve it. Making a car that excels off-road isn’t challenging; a Panda 4×4 performs quite well. Designing a car with a large load capacity isn’t tough; a station wagon can carry a lot. Now, imagine a vehicle that can hit 200km/h, excel off-road, and carry as much as a station wagon. You’ll likely end up with a large, expensive SUV. Now, think about building that SUV with a Panda’s budget; the quality will inevitably plummet.

This reasoning also applies to lenses, which is why I never purchase zoom lenses with overly wide focal ranges.

Advantages of prime lenses over zoom lenses:

  • Bright prime lenses are more affordable than bright zoom lenses. It’s common to see low-cost prime lenses with apertures below f/2.8, whereas zoom lenses with such apertures are expensive. For instance, the Nikon 35mm f/1.8 (prime) costs around 150 euros, compared to the 2000 euros for the Nikon 24-70mm f/2.8 (zoom).
  • The sharpness of a prime lens is often superior to that of a zoom lens since it doesn’t have as many moving parts.
  • Better control of aberrations and distortions. Zoom lenses at wide-angle focal lengths tend to suffer from barrel distortion, while at longer focal lengths, the performance difference is less pronounced.
  • Lightweight and less bulky than a zoom lens.

Disadvantages of prime lenses compared to zoom lenses:

  • They are less versatile; to change the focal length, you must change the lens mounted on the camera.

When working with prime lenses, to address the versatility issue, I mount a wide-angle lens on one camera and a medium telephoto on another. I keep both cameras within reach. This way, I can quickly switch between wide-angle and medium telephoto as needed.

MACRO LENSES

A macro lens is typically used to capture extremely sharp images of subjects up close. It’s not uncommon to see it used for photographing flowers, insects, products, and so on.

These lenses are used to achieve a reproduction ratio of the subject equal to or greater than 1 (≥ 1:1), meaning the size of the image on the sensor is the same as or larger than the subject’s actual size. Generally, macro lenses have a very short minimum focusing distance, about half of that possible with a standard lens. However, this distance isn’t fixed and can vary depending on the lens.

Depending on their focal lengths, macro lenses are used differently in macro photography:

  • From 45mm to 65mm – photography of products and small objects.
  • From 90mm to 105mm – insects, flowers, and small objects from a comfortable distance.
  • From 150mm to 200mm – insects and other small animals where working from a distance is necessary.
Example of a macro photo – Image by Egor Kamelev

TILT-SHIFT LENSES

Tilt-shift lenses are very unique and expensive. By loosening a screw, it’s possible to shift the lens, allowing the front part of the lens to move vertically or laterally relative to the optical axis.

These lenses are typically used in architectural photography. For instance, if we try to photograph a building by tilting the camera upwards, we’ll notice that the lines become convergent towards a point. This doesn’t happen with a tilt-shift lens, which allows us not to tilt the camera and therefore achieve a photo with perfect perspective.

Photo taken with the Canon TS-E 24mm tilt-shift lens, all building lines are perfectly straight – Photo by Dino Quinzani.

It should be noted that this type of lens doesn’t always produce artistically pleasing results, as sometimes having converging lines can be visually appealing. This lens was designed for professional architectural photography and for landscape photography that is as true to reality as possible.

With this kind of lens, we can also create perfect panoramic photos without the need for a panoramic head to avoid parallax and alignment issues. All it takes is a shifted shot to the left, a central shot, and a shifted shot to the right, then merging the images in post-production.

Panoramic photo taken with the Canon TS-E 24mm f/3.5L II tilt-shift lens – Photo by John Cunniff.

Another interesting feature of these lenses is “tilting”, which allows for control over the depth of field by tilting the optical axis relative to the focal plane. Thanks to this, we can achieve selective focus, directing it precisely where we want.

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