getitdigital reviews: A quick lesson in Aperture

This getitdigital review is part of an ongoing project to help you get better pictures.

How does one control the depth of field in a photograph? In other words how do you make the background blurry and make the subject “Pop” out of the picture?

The answer lies in manipulating the aperture. The aperture is how wide the lens can open. It is measured in SLR photography by F-stop. F-stop is measured conversely. In other words,  a smaller number F-stop actually equals a larger opening and when the number for the F-stop is higher the aperture is smaller.

The secret can be summed up in one sentence. When the lens is open wider, the aperture is increased, the background becomes blurrier.

There is one thing to keep in mind and that is that by increasing the aperture you are also letting more light in to the camera. Plainly put this means that when the lens is wide open unless you do something to minimize the light getting on to the sensor, you will have pictures that are too bright. This effect can be offset by increasing the shutter speed. When the shutter opens and closes faster, less light hits the sensor. Shutter speed is measured in seconds or parts of a second. For instance, 1/25 means the shutter opens and closes within 1/25th of a second.

Let’s put it in to visual form. As you can see, as the aperture increases (F-stop number decreases), the shutter speed increases and vice versa. The Nikon D90 was used for the following photographs.

Settings: f3.5 - 1/125

As you can see the larger the aperture, the shallower the depth of field . You can see the first coffee container clearly and in focus but the containers behind it are blurred. The shutter speed has been increased to allow for the extra light entering the lens.

Settings: f5.6 - 1/80

In this picture, the aperture has been decreased slightly so you can see both coffee containers clearly but the sugar container remains out of focus. In order to compensate for the decreased light entering the lens, the shutter speed was slowed down to allow more light in.

Settings: f14 - 1/15

In this photograph a fairly narrow aperture was used in order to bring all three containers in to focus. Again, the shutter speed was reduced to 1/15th of a second, allowing enough light for a properly exposed photograph. As an aside, when you use a slower shutter speed, any movement tends to make for blurry pictures, so it is best to use a tripod.

We hope this has helped you to take better pictures and we look forward to bringing you more reviews shortly.

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