If you are new to photography, you need to understand how the combination of Lens Aperture and Shutter Speed produce the exposure of your image. If you use a point and shoot or always shoot in Automatic mode, you don’t need this. If you want to learn how to take really good photos, you need to use a camera that allows you to control the settings and understand how your camera works. If you bought an expensive DSLR (Digital Single Lens Reflex) camera and leave it on auto shooting jpegs, you probably wasted money.

This lesson is aimed at DSLR type cameras with interchangeable lenses and manual settings.

Let’s take a look at aperture.

If you have a lens with an aperture ring on it – look at the rear of your lens for a rotating ring with numbers like; 2.8, 5.6, 8, 11, 16, 32. If you have a ring like this take the rear lens cap and cover off of your lens so you can see the lens elements at both ends. Hold the lens up to a well lit object and you can see though the lens. If you rotate the aperture ring you will see a diaphragm opening or closing depending on which way you rotate the ring. Some lenses made for digital cameras are controlled completely by the camera and don’t have aperture rings on them.


You can probably see already that a smaller number, f/2 equates to more light coming through the lens. This will also allow for a faster shutter speed generally speaking than f/8 or /22. The size of the aperture also affects the depth of field in your photo which is very important and is discussed in a separate post.

Hopefully, you have noticed that a smaller number indicates a larger aperture and maybe you are wondering why this is the case. The number that you see on the aperature ring of your lens (or in your camera’s settings) represents a ratio. The ratio is derived by dividing the focal length or distance from the rear lens element to the sensor (or film) of the camera (f) by the diameter of the aperture (D). number = f/D. If you take lots of photos and set the aperture manually you won’t need to think so much about the math; only that smaller numbers mean more light reaches the sensor and larger numbers mean less light reaches the sensor. Also, smaller numbers mean less depth of field and larger numbers mean more depth of field.

If you really want to learn this aspect of photography, and you should because it’s very important, take a lot of practice photos. Set your camera to manual mode and leave the shutter speed at something like 1/60 and take a series of photos of the same subject or scene changing the aperture with each shot. Then do the same leaving the aperture constant and changing the shutter speed. It may help you to take notes as you do this and don’t forget that your camera most likely adds a lot of metadata to your photos that you can see in most photo editing software – even Windows File Explorer shows quite a bit of the metadata.

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