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Single tired mom of four. Lover of chocolate and coffee - not necessarily in that order. Lover of Jesus, photographer by trade, Photoshop junkie and crime TV watcher.


RSS Hallie Westcott Photography

Through the Lens: Assignment 4 – What Exactly is Aperture?

September 13, 2008

Exposure is the amount of light that hits your camera’s sensor.  In order to get a proper exposure, there are four key ingredients: Aperture, shutter speed, ISO and light.

Today we are going to focus on aperture. 

Aperture, also known as f-stop, is your lens opening.  Its size controls the amount of light entering your camera.  Aperture works in conjunction with your shutter speed, which controls the length of time the shutter is open, allowing the light to hit your camera’s sensor for a longer or shorter amount of time…..

aperture = amount of light.

shutter speed = length of time light enters camera.

50mm - f/2.8 – 1/2000

The larger the opening of your lens, (smaller the f#,) the less time the shutter needs to be open to obtain a proper exposure.  Did you get that? In other words, to obtain a proper exposure you need to have your aperture and shutter speed in harmony so angels will sing. If you are confused, don’t worry, it takes time and practice.

But wait, here comes the hard part.  Hey sorry, I’m just the messenger. 

The larger the f-stop/aperture number, (F22) the smaller the lens opening.  The smaller the number (F2.8) the larger the opening.  Did you get that? Don’t pull your hair out…its OK.  Here is a little diagram to help you visual learners.


It actually seems very backwards, until you understand it and fortunately, for you I found these plumbing analogies to help you along.

Now, for each f-stop, the amount of light is doubled; however, modern cameras often support third, or some even half stops.  Below is a full stop scale and below it, third stop scale, (with full stops in bold,) that you may see when using your camera.  I am not sure how many f-stops are available if you have a point and shoot; however,  I do know there are fewer than on a DSLR.


Standard full stops scale:

2.8, 4, 5.6, 8, 11, 16, 22


Third stop scale:

1.0, 1.1, 1.2, 1.4, 1.6, 1.8, 2, 2.2, 2.5, 2.8, 3.3, 3.5, 4, 4.5, 5.0, 5.6, 6.3, 7, 8, 9, 10, 11, 13, 14, 16, 18, 20, 22


Depth of field:

And I bet you thought I was done.…..aperture also controls what is known as depth of field.  This means, the wider your lens opening, the softer your background will be and less of your photo will be in focus.  The smaller your lens opening, more of your photo will be in focus.  Did you get all that?  Here is an example.  Do you see how the background is very blurry and soft?  This was taken with a large aperture, (small f#.)


105mm – f/3 – 1/400


If you haven’t already, turn your camera to Aperture priority mode and start to play around with your aperture settings.  When you are in Aperture priority mode, the cameras shutter speed will be set for you, so it is one less thing you have to worry about.


Take an object, set it on a chair or table in a nicely lit location.  Use a table or tripod, to avoid camera shake.  You will need this when you shoot in smaller apertures, (larger f#’s,) because the shutter speed will be slower, which can result in blurry photos, if you do not use a tripod or a stable spot to prevent camera shake.


Now try different aperture settings from smallest f-stop to largest, upload your results to your blog and come back to link up with Mr. Linky.


Click this photo for a larger view.


This is the quickest and easiest way to understand all the technical things I just rattled off.  It took me a couple of weeks to really wrap my mind around aperture, so don’t be frustrated.  As you practice and view your photos, you will begin to understand the way things work.  There are no shortcuts.  Practice, practice!  

Photographic Inspiration:

Interestingness  – This is one of my FAVORITE sites for inspiration!

Previous Assignments:

Assignment 1 – Getting to Know Your Camera

Assignment 2 – Understanding White Balance

Assignment 3 – Better Composition


Digital frame by K. Pertiet



  1. carrie-the gremlin wrangler says:

    are those soup boxes? I don’t think I have any of those.

    just kidding. I’ll find something else. I think I have marbles. I’ll use the ones that fell out of my head.

    September 13th, 2008 at 11:45 am

  2. leigh says:

    I’m so excited about this lesson. This is exactly what I wanted to learn. Thanks Halli!

    September 13th, 2008 at 7:42 pm

  3. carrie says:

    i just linked to my flickr pic. hope that’s ok!

    September 17th, 2008 at 5:05 pm

  4. Marsha says:

    Now THAT is a fantastic explanation!!!

    September 24th, 2008 at 9:36 pm

  5. terry says:

    Hi there,

    I have just discovered your web site a few days ago and found it very very interesting. Are there any more instalations to follow and if so, when will the next one published.



    January 1st, 2009 at 8:25 am

  6. Beth Simmons says:

    Here is a link to my assignment four project. I couldn’t figure out how to link it with the Linky thing this time. Hallie, I’m so glad you came back:)

    February 22nd, 2009 at 3:30 pm

  7. BeckyB says:

    I was going to post mine to Mr. Linky but couldn’t figure out where the spot was to add it!!! :)

    February 22nd, 2009 at 10:23 pm

  8. BeckyB says:

    I was going to post mine to Mr. Linky but didn’t see where to add it. :)

    February 22nd, 2009 at 10:24 pm

  9. TJ McDowell says:

    Also keep in mind that the closer you are to your subject, the more out of focus the background will be. So setting your aperture to 2.8 and focusing on something close will really blur the background.
    TJ McDowell´s last blog ..Wedding Photography Tips To Get Amazing Images My ComLuv Profile

    September 10th, 2010 at 4:00 pm

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