F What?

Today I’d like to explain what aperture is, hopefully in such a simple way that anyone can understand it, then provide some visual examples of photos taken with different apertures so you can see how to utilize it in your photography.  The literal definition of aperture is very simple.  It is the size of the opening light travels through on its way to the sensor inside your camera.

Aperture is measured in F-stops.  This is where it gets a little confusing because the smaller the number of the F-stop, the larger the aperture is.  F1.8 is a large aperture.  F22 is a small aperture.

Aperture is one of the three components that combine to form the exposure of a photo, the others being the ISO speed and the shutter speed.  The larger the aperture (meaning a smaller F number), the lower the ISO can be or the faster the shutter speed can be, or a mix of both.  A smaller aperture (larger F number) means that the ISO must be higher or the shutter speed must be slower to get the same amount of light in the photo.  What does all of this mean?  To oversimplify things, it means that having a lens that can shoot at a larger aperture allows you to to take pictures in situations with less light and have the photo properly exposed without introducing noise (due to higher ISO) or having blurry photos (slower shutter speed).  Logically, this should make sense since the larger aperture lets more light in.

Aperture is also one of the two main components in photography that influence depth of field.  A larger aperture (again, a lower F number) causes a shallower depth of field, meaning that less of the photo is in focus.  This is most easily explained with an example:

Flower Photo at Different Apertures

Each of these pictures was taken in Aperture Priority mode (meaning you choose the aperture for the photo and the camera automatically determines the appropriate ISO and shutter speed) starting at F1.8 in the upper left corner and continuing to F22 in the lower right corner.  As you can see, as the aperture gets smaller, the amount of the photo in focus increases.  At F1.8 the outer petals of the flower aren’t in focus and you can’t tell what the background is.  At F5 and F11 the flower is completely in focus and the background is becoming increasingly more clear, and by F22 the background is pretty much in focus.

Take a look at the photos above again, especially the F1.8 and F22 photos.  It should be pretty clear why you’d want to use a large aperture on a photo like this.  At F22 the photo looks cluttered, everything being in focus distracts your eyes from the flower, the main subject of the photo.  Compare this to F1.8 where the background is little more than colors and blurry shapes; the flower being the only thing is focus draws your eyes instantly to it and keeps them from being distracted.

As I already mentioned, the other advantage of having a camera and lenses that can shoot with a higher aperture is that you can take better low light photography without the photos having as much noise or blur to them, especially if you’re shooting without a tripod.

I hope you find this information helpful.  Until next time, happy shooting.

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