October 15, 2012 0

Aperture and Depth of Field

Aperture is a word which is used a lot within photography and for myself was the single most confusing aspect when starting with my camera, this post will hopefully help you understand how aperture works and how you can change settings to give yourself the image you were looking for.

Using your aperture within a manual mode can give effects using DOF (Depth Of Field) which we will cover later in this post where the background of the photograph is blurred while the subject is sharp. Aperture changes also allows you to use a higher or lower shutter speed as required for certain high speed or long exposure shots.

The measurements are called “f” stops, and are given as a number. The confusing part is that the smaller the number, the larger the aperture (and the larger the hole is, and the more light can enter the camera). A small aperture is a small hole, but a large “f” number.

A large aperture would be “wide open” f/2.8 for example and a low aperture would be f/22.

Aperture can be shown below as the diaphragm within your camera change to restrict or de-restrict the amount of light hitting your sensor, f/2.8 = more light and f/22 = less light.

When using your camera in A mode (Aperture Priority) this means the camera will make auto changes to the shutter speed of your camera only, leaving you in control of the aperture of your shot.


“Bokeh” is an effect where the background of your photograph is blurred but the subject is sharp and can be used to create some very unique images.

Changing from one low f/stop to a high f/stop will change how the light hits your cameras sensor, a low f/stop will create a blurred background to your image while a high f/22 will make the background seem more in focus.

You can see from the below comparison between f/22 and f2.8

The example above shows the 2 extremes that changing aperture can achieve, the more “open” your lens is will blur the background more.

Although the A (Aperture Priority) mode is the easiest way to gain “Bokeh” the same results will also appear in other manual modes.

What’s my lens capable of?

Not all lenses will be able to “open” as wide as others, usually the lenses which can open very wide upto f/1.2 are very expensive, but this isn’t a case for all lenses, most manufacturers have something called “Nifty Fiftys” these are 50mm lenses usually with a f/Stop of f/1.8 are often their cheapest lenses.

You can find out what the lowest f/stop of your lens is by the markings on the body, in the example here, the Nikon 24-70mm is a constant f/2.8 therefore it only shows this, some other lenses will change and will display as f4-f8 for example.

This will mean that the lens can operate at a lowest f/stop of f/4 at one zoom and f/8 at the longest zoom.

If you want the maximum “blur” in your backgrounds you should get the lowest f/stop you can afford.

Sweet Spots

Another phrase that you might have heard is “sweet spot” this is where the lens operates at its best and most sharpest possible.

Most lenses perform very well at lower or higher f/stops however there maybe some parts of your image which maybe out of focus near the edges of the frame.

Every lens will have a “sweet spot” this is where the aperture of the lens produces the best quality image in terms of focus and sharpness, usually these are around f/8 however this varies from lens to lens so try taking a few images at different f/stops and find your sweet spot.

Hit the tutorial section to learn more about your SLR and what you can do with it!

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