The Three Pillars of Photography: #2- Aperture

July 08, 2014  •  Leave a Comment

Aperture, ISO, and shutter speed are the three pillars of photography exposure. These three lay the foundational knowledge in order to get the most out of your camera equipment and show off your creativity.  This is blog post #2 on Aperture. If you missed my first post on ISO, you can find it here.

In my opinion, understanding aperture is the first step to better photography. When I'm photographing, my camera is set in aperture-priority mode (not manual) 90% of the time.  I want you to be comfortable to move your camera dial from “Auto”  and onto "A" (Nikon), or "Av" (Canon), or whatever symbol your camera manufacturer uses to designate aperture-priority mode.  The why is simple; shooting in aperture-priority mode will be the first tool in your arsenal to more creative photos.  Selecting the aperture is one mechanism by which you control the amount of light hitting your camera’s sensor.  And light, my friends, is the soul of photography! 

So if you ever have muttered any of the questions below, this article is your decoder to understanding the basics of aperture and improving your photographic skills. If you know the answers to the questions below, then go find a funny meme to email friends or buzzfeed article to entertain yourself.

  • What is aperture?
  • Why do photographers write f/1.4 or f/22 in their descriptions?  Are they telling me anything useful?
  • What does a lense have to do with aperture or f-stop?  Isn’t that why I bought this expensive camera?
  • Does aperture really effect my photo?
  • What is “stopping down?”
  • What is “stopping up?”
  • If I’m meant to “stop up,” then why are the f-numbers lower?  Should that be the other way around?
  • What is a fast lense?  Should I be worried if mine is considered slow?
  •  I shoot with my camera in Auto mode.  Is there any reason to change to another mode?

So let’s start to simplify this mystery and get you on your way to better photos. 


Aperture Simply Explained

The aperture is the size of the opening in your lens.  When you press the shutter release button to take a photo, the aperture is the size of the hole that opens in your camera to let your camera sensor record the scene.  It dictates how much light will be allowed to develop the exposure. 

Aperture is measured in f-stops (“f” stands for focal).  The catch is that f-stops are measured by fractional values so it seems counterintuitive, at first, that a higher number allows less light to hit the camera's sensor.  I guess someone was trying to keep this a secret or wanted to over-complicate the matter; regardless, you just need to remember the following:

The lower the f-stop number, the larger the aperture allowing more light into the camera.

f/1.4 means lots of light will hit the camera's sensor.

The higher the f-stop number, the smaller the aperture allowing less light into the camera.

f/16 means not a lot of light will hit the camera's sensor.

Aperture Cheat SheetThe lower the f-stop number, the larger the aperture allowing more light hit the sensor. The higher the f-stop number, the smaller the aperture allowing less light hit the sensor.

So if someone recommends “stopping down,”  he or she means to decreasing the size of the aperture (increasing the f-stop number) to decrease the amount of light.  If someone tells you to “stop up,”  he or she wants you to increase the size of the aperture (decrease the f-stop number) to allow more light.


How Does Aperture Shape Your Photo?

Aperture directly affects the depth of field (DoF) of the photograph, or how much of the photograph is in focus.  This is the secret to creating those neat photos of background blur, aka Bokeh.

The lower the f-stop number (f/1.8), the smaller the depth of field meaning that more background blur will occur.

The higher the f-stop number (f/22), the larger the depth of field or more in focus the entire photo will be (focal point and background).

The first important note is that selecting an extreme f-stop setting will affect your shutter speed when you have your camera in aperture priority mode. Ignoring ISO for the moment, the higher the f-stop number will result in less light hitting the sensor.  To properly expose the image, the camera will require the shutter to stay open longer (so it gets enough light to "see" the image).  The longer the shutter speed, the more likely you will need a tripod to capture a sharp image.

The second note is that the distance between your focal point and the background will affect your photo.  In the example image, the flower is about 10 feet or more away from that back hedge.  If I can place the orchid directly in front of the hedge, the blur would not be as nearly dramatic.

For this reason, normally photographers say that an aperture of f/2.8 is pretty wide or a “fast” lense.  This is because it allows more light to enter the camera so the shutter time the shutter needs to be opened is reduced. For hand-held shots, this is critical.


How to Read Your Lens?

Each lens has a maximum and minimum aperture at which they can be used.  That is hieroglyphics on the barrel of your lens. Let’s use a Nikon telephoto lense for our example.  The following is written on the lens:

AF-S NIKKOR 70-300mm 1:4.5-5.6 G

The “4.5-5.6” tells you the maximum and minimum aperture for this lens. It means that when you shoot at the 70mm focal length, the maximum aperture possible is f/4.  Alternatively, if you zoom all the way to 300mm, the maximum aperture possible if f/5.6. If you compare that to:

AF-S NIKKOR 70-200mm 1:2.8 G

The lens is considered faster since the maximum possible aperture is f/2.8 (lots of light) regardless of the focal length you choose.


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