Have you experienced the quality of a prime lens? Most photographers have used zoom lenses. They are popular. One zoom lens tends to suit a wide range of purposes. This gives the photographer flexibility, fewer lens changes and buying one lens to do all appears cheaper. However, zoom lenses may give you a poor or soft image. In fact overall they may give a substantially poorer performance than a prime lens for some purposes.
The key to the difference between prime lenses and zoom lenses is focal length. A longer focal length magnifies the shot but reduces the angle of view. A shorter focal length widens the view in the frame. As a result of the wider view the subject in the frame appears smaller. A zoom lens allows the photographer to change the focal length.
A prime lens has a fixed focal length. The focal length is the distance from the lens to the sensor where the focus is achieved. To change the size of a subject in your shot using a prime lens you need to move closer or further away from the subject. The fixed focal length is achieved using a simple arrangement of glass elements.
Zooms use a complex arrangement of glass elements in the lens. You zoom your lens to make the image fit the frame. As you zoom you are moving the glass elements closer or further from the sensor in the camera. The complex arrangement of lens elements allows this movement to change the focal length. To allow for the movement and to change the focal length there must be more lens elements, motors and complex control technology in the lens body.
What are the advantages of a prime lens?
- Any movement in your lens is achieved by moving parts. The more moving parts you have the more difficult it is to get a sharp image. In zooms the complex technology can mean quality is lost. Prime lenses are typically much sharper than zooms.
- Composing an image is more immediate when you have to walk around to fit the shot in the frame. Most photographers think more carefully about composition when you use a prime.
- Prime lenses tend to use fewer lens elements than a zoom. Fewer lens elements mean it is easier to maintain sharpness.
- Each glass lens element tends to absorb or scatter light. Less glass reduces this light loss.
- Fewer glass elements in the prime lens means it can be a lot lighter and more compact than a zoom.
- Fewer elements in a lens mean that optical and colour distortion is reduced.
- Prime lenses are often cheaper because they have less complex glass elements, motors and technical equipment in them.
- Primes are often of simple construction. It is easier to give them wider aperture as a result. A wider aperture gives superior low-light performance and shallower, more controlled depth of field.
So, the zoom lens you have may give you more flexibility with your shots. However, it may be compromising the quality of the shot.
Prime lenses give great results and are fun when composing a shot. It is worth trying one out. As with all lenses you need to practice with them before you will get the best from your lens.