Tag: photography basics

Understanding camera terminology can be intimidating. When learning about photography for the first time as a fresh 16-year-old, the whole terminology behind the camera, and sitting in a lecture about how the camera works, did nothing for me. I wanted to be out there with my DSLR taking a photo and learning on the go. Not sitting learning the intricacies of what glass was first used for lenses and how it was made! So I have taken it upon myself to keep things a bit simpler when sharing the art of photography. Onto something that baffled me for a while, focal length – what is it?

What is it?

Focal length is the basic description of a lens. It is not a measurement of the actual length of a lens, instead, it represents a calculation (in mm) of an optical distance from the point where light rays converge to form a sharp image of an object to the sensor at the focal plane in the camera. The length calculation is determined when the lens is focused at “infinity.” That’s the scientific explanation of what focal length is. But what does that mean?

Lens length tells us how much of the scene will be captured (angle of view), and how large individual elements will be (magnification):

The human eye has an equivalent focal length of 45mm.

The longer the focal length, the narrower the angle of view and the higher the magnification.

The shorter the focal length, the wider the angle of view and the lower the magnification.

Using Focal Length

It’s all well knowing what it is, but how do you use it in a practical application?

Wide Angle Lenses
Usually any lens under 50mm. These are practical for landscape photography, as well as interiors.

Prime 50mm Lenses
A prime lens refers to a non-zoom/telephoto lens. It has a fixed focal length. 50mm is the closest to our eyesight. It is what most photographers use for portraits.
This image has a length of 50mm at f/1.8.

Telephoto 70-200mm Lenses
Telephoto or zoom lenses refer to lenses that can move between two focal points. A popular one is 70-200mm or 70-300mm.

Super Telephoto 150-600mm
A length over the 300mm mark is popular for nature photography or sports. Personally, I used the Sigma 150-600mm for bird photography, as well as sports photography.

Finding The Focal Length

The length of your lens is marked on the front of the glass, as well as on the side of telephoto lenses. The information is stored within the metadata of your photos and available to see in editing programs, and the raw file itself.

What is it? (in Numbers)

If you want to get into the details of angles, here is a conversion of focal length to the angle of view:

It is important to remember that the angle of view can cause distortion of an image. This is why using the lens correction function is so important in editing, especially with images of people!

Now if you have any questions – feel free to comment or contact me.

For more photography posts look here.