Lenses (Part 1) – Introduction

By now, if you’ve been following this blog, you should know a bit more about how cameras work, how an exposure is made, and how to juggle between the various exposure modes. We also covered a number of tutorials dealing with the exposure triangle and obtaining a “correct exposure” for our photos. If any of the above is not ringing enough bells in your grey matter, then you can easily go back to the respective tutorials by clicking on the relevant bold text above. If, on the other hand, you wish to delve into another theme, you’re in the right place. This entry will introduce the theme of lenses.

First off, let’s define what a “lens” is, as otherwise the entire entry would be pointless. Some definitions from the world-wide web follow:

  • “a piece of glass (…) with curved sides for concentrating or dispersing light rays“…
  • light-gathering device of a camera”…
  • “a lens focuses (…) the direction of movement of light”.

In layman terms, a lens can thus be said to be an object (typically made of glass) that allows light to enter from one side, and exit from the other in a “modified” way. What the lens does, in fact, is to “bend” the light towards a particular direction. What this does, in photographing terms, is help you “paint” a picture on your film or sensor, (the latter “record” whatever light touches them). To use a metaphor, you can look at the lens as a “funnel” that moves a large body of water (light) from its top part down towards a very narrow exit at its bottom, into a container of your choice (the sensor or film).

In a camera, the lens is needed to make the objects you want to photograph “appear” on the film or sensor. The lens can make the object look bigger, smaller or life-size, depending on the type of lens it is. In layman terms, we often refer to this as the “zoom” factor of the lens. You might be familiar with notices on cameras that say it has a 3x zoom or a 10x zoom. Most also immediately acknowledge that the higher the “zoom” factor, the further away the lens can see, or the bigger an object can be made to appear on the camera film or sensor. So far so good.

A second important point to make is that the picture “painted” by the lens can either be “blurred” or “sharp”. Again in layman terms, the sharper the image looks, the more “recognisable” the object will be. On the other hand, if it is blurred, then the edges that make up the shape of the object would not be well defined, making it harder on the viewer to identify what is being seen. The process of interacting with the lens to make an image appear sharper is referred to as “focusing“. For now, it suffices to know that most cameras carry out focusing on their own if you half-press the shutter button. Other cameras also allow you to focus “manually”, typically by turning a ring on the lens, or pressing dedicated buttons on your camera. What focusing does to the lens is to move it backwards or forwards in small increments until the image becomes sharp on the film or sensor.

So, this introduction presented two concepts: “zoom” and “focusing“. Is knowing this enough for you? If you’re only after day-to-day snaps, it should be enough. However, if you want to take photography more seriously, there’s much more to know about lenses than what we’ve covered in this introduction.

Thus, you can expect more blogs on this theme as follows:

  • Lenses (Part 2) – Focal Lengths
  • Lenses (Part 3) – Prime or Zoom?
  • Lenses (Part 4) – Other Properties
  • Lenses (Part 5) – Specialised Lenses & Tricks

I hope this introduction has piqued your curiosity and I look forward to see you around again for the next posts. Of course, feel free to post comments if you have questions or suggestions!

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