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How to Adjust the Aperture on a DSLR

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How to Adjust the Aperture on a DSLR

Adjust the Aperture

Figuring out your aperture is important to learn in tandem with shutter speed. If you are unsure of the aperture, visit the photography tutorials on “Introduction to Aperture” and “Aperture F Number“. By going through these tutorials, we will be able to focus purely on changing the setting to best fit your photography needs for each picture you take.

YouTube video

Check your camera and see what mode it is set to. Switch the dial to the “M” or the manual mode.

Next, find the aperture button and press it to begin changing the aperture setting. It should have the marking “Av +/-” near it.

Then rotate your command dial and watch on your status screen for the number change of the aperture number.


The shortcut for the aperture priority mode is shown as either “A” or “Av”.

As a side note, the aperture is what tells the camera how much light to bring into the camera. Use a large aperture for low lighting and a small aperture for a deeper depth of field. The larger the aperture setting number, the smaller the hold will be that lets in the light.

Aperture sets how wide the lens opening is when you take a picture. The wider it opens, the more light it lets in. Also, the wider it opens up, the more blurry the background and foreground of your image.

various aperture settings diagram - Aperture Setting

When you are setting the number on your camera, the lower the number, the wider it opens. I just try to remember that the aperture is the one that is backward. The lower the number, the more light in it and the more blurred the background is. Does that make sense?

Aperture Setting Exercise

Grab your camera and figure out how to set it to aperture priority mode. (on the canon rebel, you set it to AV, and you can raise or lower the aperture by turning the dial on the top left of your camera to the right or left.

Incidentally, in order to go to the lowest available aperture on your lens, you need to have it zoomed all the way out. I think most lenses that come with the canon rebel these days have a 3.5 lens, which means the lowest available aperture to you is 3.5, in order to dial it down that far, your lens must be zoomed all the way out.)

It’s a good thing to keep in mind when buying a lens because you may want to be zooming in a lot, but the fact is you may have to be used to just getting closer to things rather than zooming if you need a wide aperture.

Find two objects, place one in the foreground, the other in the back, and slightly to the side, so it is visible. (make sure that wherever you are shooting has plenty of light!) Adjust your aperture so that it is at the lowest possible number. Focusing on the object in the foreground, take the picture. Now, raise up your aperture. If you started at 3.5, go up to 4.5. Again focusing on the object in the foreground, take a second picture. Raise your aperture up a third time, this time to maybe 5.6, and take the third picture.

Now you can compare them to each other. The background object in the first photo should be the most blurry, and slowly become sharper in the subsequent photos. In these samples, I photographed my daughters dog Black Puppy, with the less beloved White Puppy in the background.

This first photo I shot at a 1.4 aperture.

1.4 aperture - Aperture Setting

The second photo I shot at 3.2. Notice how the background is becoming slightly less blurred.

2.3 aperture - Aperture Setting

With each adjustment to the aperture setting, the shutter opens less and less wide, letting less and less light in, which changes the depth of field, or how blurry the background is. In aperture priority mode the camera will choose a slower shutter speed to compensate for the lack of light.

If the camera allows you to see the information on each shot, make a note of the shutter speeds and how they change in comparison with how the aperture changes.

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