Photography Tip: Understanding APERTURE (Part 3 of Manual Mode De-Mystified)

February 01, 2013  •  1 Comment


This series will be in parts. The overall goal will be to show you how to use your camera in manual mode to get the most control out of your camera. This is Part 3.
Understanding Aperture in Digital SLR Photography:
Aperture is the third part of the "Exposure Triangle". I've saved this for last because the first 2 parts play an important role in getting to this step. Please be sure to read Part 1 and Part 2 to get a full understanding of this part.
What Is Aperture? 
A properly exposed photo - one that isn't too bright or too dark, is a product of three variables: ISO, Shutter Speed, and Aperture. As we learned in the first two parts these are how long the the camera's sensitivity to light (ISO), how long the image sensor is exposed to light (Shutter Speed), and amount of light the lens lets in (Aperture), in that order. In plain English, Aperture is like an adjustable "hole" (diaphragm) in the lens that allows light to reach the sensor. The larger the diaphragm opening the more light, the smaller the diaphragm opening the least amount of light.
  • SMALLER apertures allow LESS light to reach your camera's sensor
  • LARGER apertures allow MORE light to reach your camera's sensor
Aperture directly affects "Depth-of-Field". I don't want this to get too complicated but depth-of-field is the area of the image that appears sharp. I will explain more throughout this article.
How Is Aperture Measured?
Aperture is measured in F-Stops and the confusing part of this is that the lower number, say f/2.8, actually allows more light to come into the camera and reach the sensor. The typical aperture range of your lens may be f/2.8, f/4, f/5.6, f8, f/11, f/16, f/22 and on.
One thing to remember is that the smaller number means the diaphragm is open more. This can be confusing but it is something you need to understand to get a grip on exposure. So, in aperture, f2.8 on your lens lets more light reach the sensor than f/22. This example may help you understand:
Aperture scaleAperture
All lenses have a limit on how large or how small the aperture can get. The maximum aperture of the lens is much more important than the minimum, because it shows the speed of the lens. A lens that has an aperture of f/1.2 or f/1.4 as the maximum aperture is considered to be a fast lens, because it can pass through more light than, for example, a lens with a maximum aperture of f/4.0. Lenses with large apertures are better suited for low light photography and also cost a lot more. 
This is also where depth-of-field comes into play. The larger the aperture (f/2.8), less of the surrounding area is in focus.The smaller the aperture (f/16), more of the surrounding area is in focus. An example would be in a portrait, where you would want to concentrate on the subject and have the background blurry. For that you could use f/2.8 or so. For a landscape, where you would want more to be in focus, you could use f/16.
Here is an example of a shot I took for a client that used an aperture of f/4 to produce a nice dreamy background effect:
Example of depth-of-fieldIMG_2893-1
In this example you can clearly see the effect of aperture on depth-of-field. With the setting of f/4, I wanted just the face of the dog to be in focus. A focused background would have distracted the viewer. With this setting the dog's face is very focused and clear and the blurry background helps frame the subject. A blurry background effect like this is called "Bokeh" and people will buy specific lenses that have an excellent bokeh.
If you look through my galleries at the photos I sell, you will notice that most of my photos have a very sharp and detailed look. I use a higher f/stop in most of my photos to achieve this detail. To get that detail, I use a tripod almost all the time. This gives me the most control over the subject.
In this next example, I wanted all the detail I could get in the shot. I wanted the rocks to have as much definition as possible. In the version that I sell on this site, you could see and count every shingle on the roof and every rock on the beach: 
Example of depth of fieldIMG_7791-2
The day I took this photo was overcast and gloomy. I used that to my advantage and what I got was a dramatic photo of one of the most photographed lighthouses in the world. This photo then became more of a "Hitchcock" type photo and I have received many compliments on it. The settings for this one were: ISO 200, SHUTTER SPEED 1/80, and APERTURE f/13.0
So, one of the most important and confusing parts of aperture is that the smaller the number the bigger the opening and the larger the number, the smaller the opening. This is the most confusing parts of aperture for new users.
In plain English: Aperture is the size of the lens opening (diaphragm inside the lens).
I found this cheat sheet on the web. It explains all the facets I will try to explain in this series (Not my image and I couldn't find anyone to credit for it):
Photography Cheat Sheetcheat

Any questions so far? I encourage you to ask questions and comment here please. If you can add to the conversation, please do.

Feel free to comment and ask questions. I am giving this information which I hope you will find useful. This is not the end-all of photography information and I am not going into any real technical detail for advanced photographers. I'm trying to present this in a "plain-English" format for the beginner that wants to understand and improve their photographic skills. I am not a teacher. I am just trying to help. The steps here are how I learned and what opened the door to the world of photography for me. The more you know how your camera works, the better photographer you will become.

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Great read, thank you for posting this and also for including the pictures.
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