If you have dabbled in photography before, you will have heard the term focal length, and you might have wondered what exactly that is. Does it affect the sharpness of the image? How exactly does it work and what effect does it have on the image?
There are countless questions to be answered when it comes to the complicated world of photography. In this article, we will be looking at focal length, what it is, to gain a basic understanding of how it works, and whether it affects the sharpness of the image.
What Is Focal Length?
The focal length does not have anything to do with the size and dimensions of a lens, in fact, it is much more complicated than that. So, what is it exactly? Focal length is an optical property of a lens, in other words, it measures the distance between the optical center and camera sensor, and is measured in millimeters.
Each lens is named after its focal length, so for example a lens might be called a 50 mm lens and this name comes from the focal length of the lens itself.
But, what is an optical center? In basic terms, it is a group of lens elements that are used to help focus light and minimalism distortion in the image. The point at which all the light converges to create that sharp image is known as the optical center of the lens.
It is important to note that the focal length comes from the lens itself, and the camera does not particularly affect it. So, what kinds of focal length lenses are there?
Different Focal Lengths In Lenses
There are a lot of different lenses, with a variety of focal lengths. The most common of these lenses are as follows:
- 4 mm – 14 mm is a Fisheye Lens: A lens with this focal length will have a kind of fisheye effect, which means that the image will look curved and distorted as if you were looking through a fish’s eye. In short, the image is distorted and appears convex. This effect is often used for abstract or creative images or films.
- 14 mm – 35 mm is a Wide Angle Lens: A lens between these focal lengths is typically used for landscape and architecture. It has a wide field of view and allows you to capture cast landscapes. It can even be used in a room to make it appear larger and more expansive.
- 35 mm – 85 mm is a Standard Lens: This kind of lens is close to the human eye and is best used for things like portraits. It is great if you want to be able to capture some background elements but still want to be close enough for intimate shots like coverage or portraits.
- 35 mm – 200 mm is a Macro Lens: This kind of lens is best if you want close-up or extreme close-up shots. This is a great focal length for taking pictures of tiny things and making them look larger than life. So if you want to photograph a chess match, this kind of lens allows you to take awesome pictures and make it look big and impressive.
- 135 mm+ is a Medium Telephoto Lens: This kind of lens is frequently used to shoot from a distance, capturing things like sport, wildlife, or portraits. It is also one of the favored lenses for portrait photographers, this is because the lens compresses the subject and also allows you to blur the background. This makes it really easy to focus on your subject more than the background.
- 300 mm+ is a Super Telephoto Lens: This kind of lens is great if you want to be able to capture an image that is further away. So capturing sport from a distance, wildlife from a distance, or astronomy. This is one of the preferred lenses for wildlife photography because you do not need to get close in order to get a great picture.
So, What Does Focal Length Affect?
The answer to this question is quite complex. Focal length can affect the aesthetic of your image, reshaping the whole look of your background. It can also affect your image’s depth of field, this basically means that it will affect what will be in focus for the camera.
If you want to achieve a shallow depth of field, for example, you will need to get closer to the subject you want in focus and use large focal lengths like 50 mm that have wide apertures. Focal length can greatly affect your images, the main ways being the field of view, and how compressed the background is.
If you use a 12 mm lens, for example, and take a picture of a person on a bridge, you might notice that all the perspectives in the image are exaggerated. This kind of lens also greatly affects the depth of field, meaning that you can see most of the background and the subject in focus.
If you wanted to use a 35 mm lens for the same setting, a person on a bridge, you will probably find that the bridge in the background seems much closer, like we have zoomed into the background a little more. The focal length will still be quite wide, but now the subject will start to feel isolated within the image.
Using a 100 mm lens will flatten the image and the bridge in the background will continue to appear closer than the lens before. As the depth of field gets shorter, the subject will appear more isolated than before. That is why this lens is typically used for mid-shots or portraits.
A 200 mm lens will have your background fully compressed, the subject will appear much closer to the background than before and will appear blurry in comparison to the person on the bridge.
Will Focal Length Affect my Image’s Sharpness?
The short answer is yes. If you use a lens that has a longer focal length, you can easily lose the sharpness in the image. This is not because of the lens, but rather because the subject has moved. A slight movement in a lens between 200 mm and 400 mm will be very noticeable.
But, how sharp an image is will not be consistent even if you use one lens. This is because even that can change with aperture, subject distance, or even the type of lens you are using.
A zoom lens for example may allow you to adjust the focal length without changing the lens itself, and a prime lens will only have one focal length. This means you will have to be very aware of what each focal length does for your image and take into consideration how you want your image to look.
In conclusion, it is important to understand that focal length plays a huge part in photography and can affect a lot about the image. The longer your focal length, the more compressed the image will appear and the narrower the field of vision will be.
It is because of this that focal length can affect the sharpness of an image. The larger the lens, the harder it will be to get a sharp image, this is due to the lens or camera movement.
A longer lens like 200 mm will have a smaller area of view, which means that a slight movement from your subject or front of the camera itself will be easily noticeable.