An Aperture Mantra

Aperture is a strange concept when learning photography.  Aperture is defined as the size of the opening in the lens that light passes through before it hits the photographic medium which, these days, is an electronic sensor at the back of the camera.  Aperture is also measured in some strange language called f-stops.  F-stop numbers look to defy logic as the larger they are, the smaller the size of the aperture and the larger the focus area. Consequently, the smaller the f-stop number, the larger the size of the aperture and the smaller the focus area.  Confused?

Recently, Karen of Karma’s When I Feel Like It Blog, came up with what she calls a little mantra about aperture so she can remember what the f-stop numbers mean.  I found the mantra brilliantly simple.  You know, one of those “I could have had a V-8” slap to the forehead brilliant.  Here it is:

Big number, big focus area, little number, little focus area.

Let’s take this mantra out for a test drive.  Below are two photos which demonstrate Karen’s mantra.

Big number (f/16), big focus area.  Nikon D700/50mm, 1/30s, f/16, ISO 640, EV +1.0.

Big number (f/16), big focus area. Nikon D700/50mm, 1/30s, f/16, ISO 640, EV +1.0.

Notice everything is in focus from the flowers all the way back to the mural, a big focus area.

Little number (f/1.8), small focus area.  Nikon D700/50mm, 1/800s, f/1.8, ISO 200, EV +1.0.

Little number (f/1.8), small focus area. Nikon D700/50mm, 1/800s, f/1.8, ISO 200, EV +1.0.

The classic selective focus effect by using a lens wide open at its smallest f-stop number and small focus area. Notice the change in the shutter speeds and ISO between the two photos to maintain the correct exposure.

Next time you get confused about aperture, remember Karen’s mantra, “Big number, big focus area, small number, small focus area.”  Thanks, Karen.

The mural of the firefighters in the photos is found on the side of the Cicero Volunteer Fire Department firehouse in Cicero, New York.  The photo below will give you a better idea of the distance between the flowers and the mural.

Firefighter mural on the Cicero (NY) Volunteer Fire Department house.

Firefighter mural on the Cicero (NY) Volunteer Fire Department house. Nikon D700/50mm, 1/30s, f/16, ISO 200, EV +1.0.

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22 Responses to An Aperture Mantra

  1. Karma says:

    I’m glad you liked it so much, Scott! It feels good to be able to contribute a little bit to maybe help others when I’ve received so much help from the blogging community. This is a really nice demonstration of the difference.


  2. Gerry says:

    I am so frustrated. I keep wanting a little dial, like the one on a microscope, that lets me FOCUS on the object I am interested in, as opposed to the object the little camera is interested in, which is often something else entirely. I have a deep and abiding suspicion that I have bought a camera with a mind of its own.

    In any case, this is a wonderful illustration of the point. (And you know I love the mural!)


    • Gerry, check your camera’s manual on focus settings. Sounds like it is some sort of cloud focus setting where it determines what the focus subject is and not you. I have been experimenting with something similar on my new camera. Mixed success so far but see if there is one which lets you choose where the focus point should be.

      If you are using AUTO mode, it might be time to learn how to use the other modes, too.

      I will say the photos you have been using on your blog have been excellent. You just need to master the camera (and not the other way around!).

      I thought of you and your son when I was photographing the mural. 🙂


  3. Anna says:

    LOL Neat mantra. Aperture is one of those settings I learned early. That is a beautiful and very interesting mural on the Volunteer Fire Department house in the background of the photos.


  4. JenniferA says:

    That’s my sister! Mnemonics are good.


  5. montucky says:

    I’ve found that taking macro shots of wildflowers is a good way to experiment with aperture. And thank Goodness for digital!


  6. That is a great way to remember Aperture


  7. cindydyer says:

    Very nice examples of depth of field, Scott! You’re shooting with the D700—how do you like it? I’m still on my D300 (with another D300 as a backup). I’ve worked my way up from a Fuji S2, S3, then D70, and now the D300. Love this camera, but would love a D700 full frame!


    • I love it. I’ve tested driven the D700 a few times over the last year as a friend of mine let me borrow his occasionally. I am finding I have to more careful of the aperture setting with my fast lenses. Wide open on a full frame camera is much different than on a DX one. In low light, the plane of focus at f/1.8 or f/2.8 is much thinner.

      Thankfully, shooting at f/4, f/5.6 or f/8 in low light is great since ISO from 800 to 5000 is not bad at all on the D700 sensor. Something I have to keep reminding myself.


  8. You know, when I got my very first SLR, that was the most confusing part! That darn f-stop! I pretty much learned through trial and error and at some point if figured out what the numbers meant.


  9. Nye says:

    I have a full understanding of this now from reading Understanding Exposure Revised Edition by Bryan Peterson. It was sort of a guess work for me at the beginning and I thought I had to use the small f/stop for closeup image only, and never knew that I could use it for far away image that I zoom in and want to blur the background.


  10. Carsten says:

    Thanks for the very pedagogic illustration of dof Scott.
    I found this calculator. It might show someone why it is difficult to obtain what you want when taking macro photos.
    Sorry for the metric system 🙂
    Near the end of the page is a link to more explanation – with lots of words instead of Karmas effective mnemonic.


  11. Jim says:

    You know how some people use taglines at the end of thier e-mails… ? You know – some little statement or quote, or whatever? I work in I.T. (network admin, lan monkey, advanced help desk / end user support) and as such subscribe to couple of e-mail listserves. One of the most clever taglines that I have ever seen, and have since ascribed to, went something like this:

    “… if you can’t explain it simply, then you don’t know it well enough”

    I thought (think) that this little ditty on DOF is really great. I have struggled for a quite sometime when trying to explain to people what and how DOF, f/stops, etc are and how they (basically) work.


  12. flandrumhill says:

    Excellent advice Scott for the reasons Jim cited already above.

    I could use more of this type of instruction.


  13. Pingback: As Summer Fades Away « Karma's When I Feel Like It Blog

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