Camera Lens Basics – Numbers on a Camera Lens
Camera Lens Terms
Standard: Focal length roughly equivalent to what the eye sees.
Ex. Full Frame DSLR = 40mm; APS-C = 35mm. Film SLR = 50mm.
Wide: Focal length under standard lens Ex. 24mm f/1.4
Telephoto: Focal length over standard lens. Ex. 100mm f/2.8
Prime: Fixed focal length, any mm. Ex. 14mm, 85mm, 100mm
Zoom: Ability to change focal length. Ex. 70-200 f/2.8
These terms can be combined.
- A 70-100mm is a telephoto zoom. (Ability to change focal length and the focal lengths are all over 50mm).
- A 85mm is a prime telephoto. (Fixed focal length, above standard lens.)
- A 14mm is a wide prime. (Fixed focal length, under standard lens.)
The focal length of your lens can be found in several places on the lens. Look at the end of the lens, find the your focal length and notice that there is a string of other numbers following it. These numbers indicate the Maximum Aperture of that lens.
This is a Canon 100mm f/2.8. The numbers at the end of this lens plainly indicate the 100mm. The numbers following that sometimes cause confusion. The 1:2.8 indicates that the maximum aperture of the lens is 2.8 (meaning f/2.8). Maximum aperture is the widest the lens aperture opens.
There are a few more numbers on this zoom lens. We know that the 100-400mm refers to the focal length / range of the camera lens. 1:4.5-5.6 indicates that the maximum aperture varies with the focal length.
When you’re fully zoomed out (shooting at 100mm) the maximum aperture of the lens is 4.5.
When you’re fully zoomed in (shooting at 400mm), the camera lens aperture only opens to 5.6.