Aperture confuses some photographers, which is why many use the Auto mode and miss most of the best photographs they could’ve ever taken. Aperture is an opening at the end of the lens. We often compare the aperture to your eyelid. It controls how much your eye can see. The aperture controls how much light enters the lens and it also controls the depth of field, which we cover in another lesson.

Aperture settings are referred to as f-stops. This is where many photographers stop trying to learn and simply switch their cameras to the Auto mode. F-stop numbers on most lenses range from f/1.8 to f/22.  Each f-stop lets in half the amount of light of the preceding f-stop.  Before trying to explain further, we’ll include a diagram of the common f-stops.


As you can see in the diagram above, the f/2 aperture is wide open. The f/16 is almost closed. Some people say the f-stop numbering system is backwards but it is what it is. The smaller numbers represent a wider opening. The largest number represents the smallest opening.

When you set the aperture on your camera, you’re telling the lens how wide to open. If you want it wide open, switch to the smallest f-stop.  If you want the lens diaphragm closed more, switch to a larger number. Switching to a larger or smaller aperture is called ‘stopping up’ or ‘stopping down.’ Only professional photographers use these terms but we thought we would include them in case you hear someone say you need to ‘stop up.’ That means to switch to a higher f-stop.

The aperture also controls the depth of field. In simplest terms, the depth of field indicates how much of your picture is in focus in front of and behind your subject. Depth of field is important depending on how much of your picture you want in focus. I’ve shot thousands of pictures of roses that were in a private rose garden. By choosing the right f-stop, I was able to isolate each rose while blurring out the surrounding rose bushes. We’ll discuss depth of field in another lesson. First we must explain ISO settings and depth of field.

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