Focal length. You’ve no doubt heard the term – it’s hard to avoid – so here is a quick breakdown about what it is and how it affects your photographs.
What is focal length?
Let’s get the technical definition out of the way first. The focal length is the distance between the optical centre of a lens and the camera’s sensor. It is measured in millimetres.
The focal length of a lens is identified on the lens itself (usually with a series of other letters), e.g. Nikon 35mm f/1.8G or Nikon 24-70mm f/2.8E.
What do the distances mean?
There is no hard categorisation but it is generally accepted that anything under 28mm is classified as wide angle; between 35-50mm is normal; 70mm is the start of the telephoto range; and 300mm and over is super-telephoto.
Lenses are either zooms or primes. The former covers a range of focal lengths, e.g. 24-70mm, while the latter has a single, fixed focal length, e.g. 35mm. It is common to hear lenses referred to as, for example, “wide-angle primes” or “telephoto zooms”.
Each has its pros and cons which I will discuss another time.
Wide vs. long: the characteristics
I can’t tell you which focal length you should use in a particular circumstance. Ultimately, it comes down to personal taste and style.
What I will do is share some characteristics of shorter and longer focal lengths so you know what the impact will be on your photograph.
When using shorter focal lengths:
Your field of view is wider
Your achievable depth of field increases
Distant objects appear smaller and further away
Nearby objects can become exaggerated in size
When using longer focal lengths:
Your field of view is narrower
Your achievable depth of field reduces
The scene is compressed, making distant objects appear closer than they really are