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Small Aperture Settings in Digital Photography - Opportunities and Challenges

written by: Javier Ideami•edited by: Rhonda Callow•updated: 5/24/2011

Here is a fascinating review of the opportunities and challenges presented by small aperture settings in digital photography.

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    Aperture Settings: Questions and Challenges

    One of the most common questions asked by novice photographers is regarding the aperture controls of their cameras. What is the purpose of setting a small aperture or a large one? Why does the aperture get larger when its numbers (F stops) get smaller? Such questions are very much expected of photographers just starting on an exciting journey. As a matter of fact, the numbers that describe the aperture of the lenses are the most counter intuitive parameters that any new photographer has to deal with. Therefore, this article attempts to tackle some of the pressing questions about aperture controls.

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    Numbers and Details

    To begin with, think of the aperture of your camera lens as the size of its opening. The photons of light arrive to the lens and are focused by the lens onto the sensor. The sensor records and translates the analog signal into digital numbers, which then get written onto your memory card. The numbers that describe the aperture of our lenses are typically these:

    F/1.2, F/1.4, F/1.8, F/2, F/2.8, F/4, F/5.6, F/8, F/11, F/16, F/22, F/32, F/45

    As the number gets smaller, the opening of your lens becomes larger, which means more light enters your camera. The larger the number gets, the smaller the opening of the lens becomes and therefore less light enters your camera.

    The reason why the opening gets larger with smaller numbers is because those numbers, also known as F stops, actually represent fractions of the numbers. For example, F/1 represents the full diameter of the lens you have divided by 1, which equals the entire diameter. So a theoretical lens that could have an aperture of F/1 would in fact be fully open. F/2 means the full diameter of the lens divided by 2. If you have a 50mm lens and you set the camera to, the opening of the lens will be 50/2 = 25mm. Although you have increased the number by going from F/1 to F/2, the opening of the lens has decreased from 50mm to 25mm since the F numbers represent a fraction of the diameter of the lens.

    In the same way, F/8 in a 50mm lens would mean 50/8= 6.25mm. Therefore, the opening of the 50mm lens gets smaller and smaller as we increase the F numbers of our aperture settings.

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    Uses of a Small Aperture

    And what is the usefulness of setting large or small F numbers? This article will focus on small aperture settings.

    Traditionally, we consider F numbers like F/11, F/16, F/22, and F/32 as small apertures. Therefore, large F stop numbers produce small apertures in your lenses. As a consequence of setting a small aperture, the depth of field will increase. The range of the scene that will retain sharpness and stay in focus will be larger. At the same time, since the opening of the lens is smaller, the amount of light that enters our camera will be less.

    On one hand, the increase in the depth of field (also known as DOF) is particularly useful for landscape photographers. When you are photographing a landscape, you want to keep a very large range of the scene in focus. Therefore, you need a very large depth of field, which is easier to attain with a small aperture.

    On the other hand, since you are bringing less light into your camera, you will need to set your camera to use a slower shutter speed. However, this will make it easier to get blurred photos due to the movement of the camera. To use the fastest shutter speed as possible, you have two options: you either increase the lighting of the scene (which is easy to do indoors especially in a studio, but very hard to do if you are outdoors in front of a vast landscape), or you use a tripod, as most landscape photographers do. Using a tripod will allow you to take very long exposures without producing blurry images as the tripod will keep the camera stable.

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    In summary, use a small aperture setting to get a large depth of field when you need most of the scene to be in focus. To ensure that you can still use fast enough shutter speeds, combine it either with extra lighting to keep the image sharp or use a tripod to be able to take longer exposures.