What You Should Know About Lenses

Photography is a hobby for some, a business for others.  If your intent is to reproduce on film or on digital media what you see with your naked eye, buy a point and shoot camera.  A point and shoot camera will reproduce what you see only with a narrower scope than your eye takes in.  However, if you want to enhance what it is you see with the naked eye, then you need to take a look at a camera that can alter what you see with lenses and filters.

In this article there is no intent to lead you in one direction or another toward the purchase of particular makes or brands of lenses. The intent is to provide you with general information so that you can make decisions about what you want to do in your picture taking.

There are many kinds of lenses that are available, among them, macro, wide-angle, telephoto, fish-eye, and zoom.  Because of the way light entering a lens is altered by different types of lenses, something is gained by the use of a lens, and something is usually lost as well.  Again it is important to know what effect you want to achieve in purchasing a lens.  There are many things to be aware of in purchasing a lens, and we will focus (no pun intended) on focal length in this article.

You will see the term “focal length” made in reference to lenses.  The focal length of a lens is defined as the distance in millimeters from the optical center of the lens to the focal point, which is located on the sensor or film if the subject (at infinity) is “in focus”. The camera lens projects part of the scene onto the film or sensor.  Lenses are able to achieve this effect because they include multiple glasses within one lens, a compound lens.

Lenses with a focal length of 50mm are called “normal” because they work without reduction or magnification and create images the way we see a scene with the naked eye. Lenses of greater or lesser focal length either magnify or reduce the image we see.  Lenses are named by their focal lengths:

  • Super wide angle        < 20mm
  • Wide angle                  24mm – 35mm
  • Normal                        50mm
  • Telephoto                    80mm – 300mm
  • Super telephoto           > 300mm

Simply put, focal length has to do with magnification.  Changing focal length allows you to come closer to the subject or to move away from it. Focal length, therefore, has an indirect effect on perspective. If you use a fixed focal length lens, you cannot alter perspective. Zoom lenses allow you to change magnification, and therefore perspective, without changing lenses. The primary advantage of a zoom lens is that it is easier to achieve a variety of compositions or perspectives, since lens changes are not necessary.

Remember what I said about gaining and losing something with different types of lenses?  Though zoom lenses are convenient, they will suffer to some degree, depending on their quality, from some barrel distortion at the wide angle end and from pincushion distortion at the telephoto end of their zoom ranges. The choice is often between convenience and limitation of distortion.  With your choice of various lenses and filters, you will greatly enhance the creativity of your picture taking.