About Camera Lenses
Along with the camera, the lens is a key piece of equipment for photography. At a very basic level, lenses allow you to focus light onto a sensor or film and produce a clear and sharp image of the scene in front of you. Lenses also let you adjust exposure, modify the plane of focus, and different focal lengths can be used to change your field of view. They are as much creative tools as they are a standard piece of equipment and are integral to photographers capturing a scene as they desire.
Different lenses are used for different purposes, ranging from the all-in-one zooms that are great for most subjects to the more specialized and niche super-telephotos and ultra-wide-angle lenses that are reserved for select shooting situations. The variety of lens types and designs is what allows a photographer to develop a unique and personalized look.
Some of the key things to decide on when looking for a lens include focal length, aperture, prime vs. zoom, and whether the lens has any special designs or is optimized for certain use applications.
One of the fundamental considerations when choosing a lens, focal length describes the field of view you will have with a certain lens. 24mm, 35mm, 50mm, 24-70mm, 70-200mm and so on are various common focal lengths. The lower the number (e.g., 24mm) describes a wider, broader field of view; a higher number (e.g., 85mm) describes a narrower, tighter field of view.
The maximum, or widest, aperture is also included in the name of a lens, for example a 50mm f/1.8 lens. This means the lens has a 50mm focal length and a maximum aperture of f/1.8. Apertures are described in f/stops, which is a fractional way of indicating “lens speed,” or what the ratio is between the focal length and the diameter of the lens’s entrance pupil.
In simple terms, the lower the f/number, the faster the lens is. An f/1.4 is faster than an f/2.8 lens, for example. Faster lenses allow more light to enter the lens, making them better for low-light situations, and also offer more control over depth of field. The consequence of a faster lens, though, is that they tend to be larger and heavier than the same focal length with a slower maximum aperture.
Prime vs. Zoom
Lenses are either primes or zooms; “prime” indicates they have a single, fixed focal length and “zoom” indicates there is a range of focal lengths available, such as 18-55mm where the lens can seamlessly switch from 18mm to 55mm. Both designs have pros and cons:
Primes are simpler, tend to be smaller and lighter, and are usually faster than a zoom. They only offer the one focal length, though, and require changing lenses if you need to adjust your field of view.
Zooms have the inherent versatility of multiple focal lengths but also tend to be a bit larger, heavier, and slower than a comparable prime lens.