Understanding Aperture

Below you will find an excerpt from my book “Understanding the Basics of Exposure”. This will help you get a better idea of the books content as well as teach you a little about the Aperture and how it is used. If you know of anyone into photography please share this post. I believe that the book can help those just getting started as well as reinforce the basics for those who have been doing this for awhile. Enjoy this excerpt and please leave a comment and let me know what you think.


What is the Aperture?

Aperture in its basic definition is a hole in which light travels through. This opening is increased or decreased using a series of blades within the lens of a DSLR. The number that is used to indicate the size of the opening is called an f-stop. The f-stop number is determined by dividing the focal length of the lens by the diameter of the pupil (or opening). Luckily in the camera world we just have to pay attention to the numbers after the “f” to know the f-stop. Smart people somewhere already did the math.

How the Aperture is Used?

The aperture is used when determining proper exposure. If you think of the aperture as a faucet and light as water it might be easier to understand. If you turn a faucet on full blast it is letting a large amount of water flow. That would be the equivalent of a wide open aperture i.e. f2.8. If you turn the water on just slightly where there is only a trickle then you have a small aperture i.e. f22.

Not only is aperture used to help determine proper exposure but it is used to determine depth of field.

• Depth of Field (DOF)

  • DOF is the distance between the nearest and farthest objects in a photograph that appear reasonably sharp. Think of this area as the focal plane as well. Lenses can precisely focus on a given point. However, anything closer or further away from that point begins to leave the focal plane. This is how you get the nice blurry backgrounds you see in some photographs or the tack sharpness in others.
  • The smaller the opening (higher the f-stop number) the greater depth of field. Think of it like squinting your eyes.
  • The larger the opening (smaller the f-stop number) the shallower the depth of field.

•Aperture is one of the most powerful tools in a photographer’s arsenal to creating compelling images. It vital to your photography that you fully understand what changing aperture numbers will do to your photograph.

Below is a list of typical f-stops you typically see on modern lenses and a graphical representation of what happens to the depth of field as the f-stop number changes. I highly recommend that you memorize these apertures as it will help you later when you are determining manual exposures and depth of field.