Lens is one of the most important and defining factors in photography. A lens defines, to a certain extent, the quality of your images, look, depth and most importantly the feeling and the message an image conveys. In this article, I would briefly discuss what you, as a photographer, need to know about lenses so you can make an informed choice when choosing a lens for a distinct purpose. At the end of the first part you should be able to answer the following questions:
- What is and does a lens?
- What is focal length?
- What is the definition of wide angle, normal and telephoto lenses?
- What are the common intended use for each focal length?
What is and does a lens?
A lens is a single or multiple optical glasses that is used to converge the incoming light on the light sensitive part of a camera in order to create a sharp image of subjects that are in a distinct distance from the lens.
There are two important features in photography related to lenses: Focal length and the aperture.
What is focal length?
Focal length defines the level of magnification of distant subjects and also the lens’s angle of view (sensor size plays also a role here). The smaller the focal length the wider the angle of view and lower the magnification and vice versa. The focal length in millimetre, which is always depicted on a lens barrel, is not necessarily related to the physical size of the lens.
Figure 1. A lens may have a fixed focal length, in this case it is called a prime lens. A lens may also have a range of focal lengths, in this case it is called a zoom lens. In this figure the lens to the left is a zoom lens with focal lengths of 18-140 mm, the next one is a prime lens with a fixed focal length of 90 mm.
Note: Angle of view is basically how much of a scene, horizontally / vertically / diagonally, you can see when looking through the viewfinder or at LCD screen. The angle of view is related to the focal length and the size of the camera’s sensor. I have discussed this in a previous blog comprehensively.
Focal length: magnification and the angle of view
In Figure 2 top left corner, you see a vast cloudy sky covering a seemingly long road to a distant light house when photographed with a small or short focal length, which we call a wide angle lens. The angle of view gets smaller, the light house will become larger, and the seemingly long road will become smaller and smaller as we increase the focal length. The last image, bottom right corner, is no longer a landscape photo, but a photo of a lighthouse.
Figure 2: In this case an 18-140 mm lens is used on a cropped sensor Nikon, which is equal to 27-210 mm on a full frame camera (if needed read my previous blog on full frame vs. cropped sensor cameras).
Focal length: Emotional impact, perception of magnitude and distance
Regardless the terminology of the “angle of view” and “magnification”, the effect you saw in figure 2, is something most people, who hold a camera, are familiar with. In other words, focal length is often changed to get more in the image or to fill the frame with one single subject, like in portraiture.
However, focal length means much more than that and each focal length creates a unique look, and feeling, so you should not zoom in or out for convenience, but to get the look you are looking for. To visualise the effect I am talking about look at the images presented in figure 3.
Figure 3. Both images are made with a Nikon D7100 in aperture priority mode; f/11, ISO 400, manual focusing, position of the camera is unchanged. Focal length for the first image is 18 mm and 140 mm for the second one (equal to 27 mm and 210 mm on a full frame camera).
Notice how the distance between the columns are exaggerated when shooting with a short focal length and how this decreased when shooting with a long focal length. Other effect that you should be able to appreciate is the effect that focal length has on the magnitude of the columns. These columns are of the same height. When shoot with an 18 mm lens the columns closer to the lens look much taller comparing to the ones in the distance. While with a 140 mm lens the columns are of the same height. These effects are unique to each focal length and you should be aware of that when choosing a lens for a distinct purpose. These two images are made with the same camera, the same camera settings, and from the same distance. The only variable is the focal length, which results in two totally different images.
Classification of lenses based on their focal lengths
Lenses, either with a fixed focal length or a range of focal lengths, are classified in three main groups; standard (or normal), wide angle, and telephoto lenses.
- Standard lens: A lens that creates the same angle of view that is comparable to the angle of view of our eyes is a standard lens; roughly a 50 mm lens.
- Wide angle lenses; In general lenses with a focal length of 24-35 mm. But strictly speaking any lens that creates a wider angle of view comparing to standard lens, is a wide angle lens. Hence, below 50 mm on a full frame camera.
- Telephoto lenses: commonly a lens with a focal length above 70 mm. But strictly speaking any lens that creates an angle of view smaller than a standard lens, is a telephoto lens.
In addition to aforementioned lenses, there are other less common lenses, like:
- Ultra wide angle lenses: with a focal length smaller than 24 mm. Fish eye lenses that can produce an angle of view of 180 degree with a very recognisable distortion is among this group.
- Macro lenses: are prime lenses, of any focal length, that can create 1:1 magnification. Basically the image, let’s say of an insect, that is formed on the camera sensor is equal to the actual size of the insect in reality. If you are into still life photography, investing in a macro lens is a good idea.
- Swivel lenses: You can rotate these lenses when mounted on a camera to create a unique perspective and angle.
- Tilt and shift lenses: These lenses are perfect in giving you control of perspective.
Some of these lenses are very specialised and using them requires expertise and experience.
Note: The classification of lenses based on their focal lengths is always based on the angle of view they create when mounted on a full frame camera. Hence, a 50 mm lens mounted on a cropped sensor camera is no longer a standard lens. If you have a cropped sensor camera, you need to change the focal length using the crop factor of your camera sensor. To learn more about this click here.
Common intended use of each focal length
Although you should allow yourself to practice with all focal lengths and find out what they create, there are some general recommendations that might help you to begin with.
Wide angle lenses: When having the feeling of space, freedom is desired, wide angle lenses are perfect. With a wide angle lens you can be very close to your subject, hence they are intimate, and would also give the viewers the feeling as if they participate in the scene and witness what is happening. These lenses are perfect for landscape photography. Architecture photography might provide another usage for wide angle lenses. Although distortion caused by wide angle lenses is not desired in professional architecture photography. Nevertheless, this might work well for creative photography. If you are photographing real states, wide angle lenses are very good option. In addition, some streed photographers prefer to work with wide angle lenses.
Standard lens: Since these lenses have the same angle of view as our eyes, they are fantastic for documentary and street photography. Standard lens gives the photographer the chance to stay close to the subject, but not too close to be intrusive, and create images that look real for the viewers.
Telephoto lenses: This lenses create straight lines, and you are relatively far from your subjects and act as an outsider. They bring far subjects close and the distance between subjects will be small, as if everything is pushed together (see figure 3). These lenses are perfect for wild life photography, photojournalism, portrait and fashion photography. For portraiture, a lens with a focal length of 85 mm has got the reputation of being “portrait lens”. It creates an appealing look with a shallow depth of field. But in general a zoom lens of 70-200 mm is wonderful for portrait and fashion photography among other usage.
In the next part, I will discuss the aperture so you would have a brief but complete overview of the important features of a lens.
I hope this post was helpful. If you have any question or remark please send me an email.
Triangle Photo Academy