Prime Vs Zoom Lenses - Camera Lessons
By Gene Rodman
If a budding photographer looks to upgrade a lens the choices seem endless. Point and shoot cameras come equipped with a zoom lens permanently attached so I'm really talking about those with Digital Single Lens Reflex cameras. DSLR cameras also come with some type of zoom lens or several as a kit to cover a wide variety of focal lengths.
- A zoom lens lets the photographer choose different focal lengths, from wide angle to telephoto.
- Zoom lenses have the advantage of allowing the photographer to get closer to a subject without physically moving.
- They also enable the photographer a better chance of getting the shot because the photographer can compose and shoot without changing lenses.
- There is also less chance of getting dust on the sensor from constantly changing lenses.
When zoom lenses first came onto the market they were heavy and the quality of the images they produced could not compare to a fixed focal length (prime) lens. The quality has improved greatly because of computer design but there is usually a fall off of image quality as the lens is zoomed to longer focal lengths.
Back in the day serious photographers had a variety of fixed focal length lenses in their camera bag that were very sharp. They included a few fast (large maximum aperture) prime lenses: a wide angle lens (20-28mm), a normal 50mm lens, a portrait lens (80-105mm), and a longer lens (180-200mm) that could be used as a head and shoulders portrait lens or for sports and wildlife photography.
So why should a person carry all these different lenses when one or two zoom lenses could easily cover all the focal lengths and even the intermediary ones too?
There are images that you simply cannot capture with a zoom lens.
- Prime lenses let in much more light than a zoom lens. Whereas a zoom may have a maximum aperture of say f 3.5-f 5.6 prime lenses have a maximum more like f 1.4-f 2. Aperture settings (along with focal length and distance to the subject) control what appears sharp in a photograph. By controlling what is sharp the photographer can guide the viewer's eyes to important parts of the image. When you use these lenses at their widest apertures it allows a photographer to isolate a subject from the foreground and background because at these apertures depth of field is very shallow. By using selective focusing this narrow depth of field allows for only a narrow area in the image to be sharp. In a portrait it is very important to isolate the subject from its surroundings. If you look at ads in magazines you will see how selective focusing and narrow depth of field are used to isolate the product name or some point of interest in the ad. Your eye naturally moves to the sharpest part of an image.
- There are other advantages to using prime lenses. When you are able to let more light into the camera for exposure there is less of a need to raise your ISO and by doing so introduce noise into your image.
- Most prime lenses have depth of field scales on them so you can calculate what in your image will be in focus. I use these scales all the time with my scenic images because I want everything in the image to be in focus. It really bugs me when someone shows me an image where the foreground is out of focus or the background is soft because the depth of field was not great enough to encompass both the foreground and background in the image.
- Since prime lenses have the ability to let more light into the camera exposure metering is more accurate and auto focusing is faster. How many times do you have your zoom lens extended all the way and the auto focus searches for a focusing point? It is because there is not enough light entering the lens for the auto focusing and metering system to work properly.
- Prime lenses will also be sharper and focus closer than the same focal length on a zoom lens.
- A prime lens will only give you one angle of view and it is a good exercise to photograph with just one focal length. By doing this the photographer is able to discover what are the benefits and limitation of each of the lenses and their focal lengths. I feel that many photographers get lazy with zoom lenses. They won't move for a change in perspective or to get a better angle on their subject.
Zoom lenses are here to stay and as the quality of these lenses increases many will keep only one lens on their camera that will satisfy most of their needs for the way they photograph. Although I see the need for zoom lenses for photojournalism, weddings and some portraits where it is important to be able to get the photograph quickly, I will keep my camera bag stocked with my favorite prime lenses and use them when I know I want the very best image I can get.
Gene Rodman is a life long photographer and owns Montana Photographic Arts Gallery and Studio. You can view his website at http://www.MTPhotoArts.com.
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