In this lesson: Learn how to use a small aperture to achieve maximum focal range

Using a small aperture size, such as f/16 or f/22, will help you create images with maximum sharpness from the foreground to the background. However, adjusting the aperture to maximize the depth of field requires you to maintain proper exposure with adjustments to shutter speed and/or ISO setting.

To achieve the maximum range of focus within an image, a small aperture is required. Recall that this area of sharpness is referred to as the depth of field. To ensure sharpness in the foreground, mid-ground, and background, landscapes and other scenes with great depth should be photographed using a setting near the minimum aperture size on a lens (the highest f/number).

A Quick Example

Let’s use the image above as an example of this concept. Note how everything in the photo from the reflection in the foreground water to the peaks of the mountains in the background is in sharp focus. This is the large depth of field we want.

As noted above, achieving that large depth of field is dependent, in part, on the aperture setting you use: the larger the aperture opening, the shallower the depth of field; the smaller the aperture opening, the larger the depth of field. Remember, the size of the aperture opening is inversely related to its f-number. So, small f-numbers, like f/4, refer to a large aperture opening. On the other hand, large f-numbers, like f/22, refer to a small aperture opening.

Shooting with a very small aperture can have a number of benefits.

Clearly Illustrate Every Part of a Subject

A small aperture, like f/16 for example, allows you to highlight every aspect of a scene. We’ve already discussed how this is advantageous for landscape images. However, a large depth of field is advantageous in other applications too. Street photography, nature & wildlife photography, and sometimes, even portraiture, as seen in the example above, benefit from having everything from front to back in sharp focus. Note how in the sample image, every aspect of the man is in clear, sharp view. This includes his body and his boat, as well as the surroundings. As a result, the large depth of field gives this environmental portrait much more context about who this man is, where he lives, and what he’s doing.

Minimize the Potential Loss of Image Focus

One of the most common enemies of high-quality images is having a soft focus, that is, parts of the image not being optimally sharp. Though shooting with a small aperture to create a large depth of field won’t resolve this problem perfectly every time, it certainly minimizes the chances that part of your subject or the scene you’re photographing will be out of focus.

Take a look at the image above. Note how everything from foreground to background is sharp and in focus, from the people in the crosswalk to the vehicles in the street to the distant buildings in the background. Everything is tack sharp, due in part to using a small aperture.

Create Star Effects on Bright Points of Light

The starbursts seen in the image above were created as a result of diffraction. Essentially, diffraction is the process by which light waves bend and spread out through small openings. Therefore, when light enters your lens through a small aperture like f/22, its waves bend around the edges of the aperture blades, the result of which is the starburst form. Note that the number of rays emanating from the starburst depends on the number of aperture blades. In this image, there are eight rays, but in your image, there might be more or less.

A Word About Exposure

Reducing the aperture size to maximize the depth of field also reduces the quantity of light passing through the lens. As a result, the shutter speed and/or ISO setting must be adjusted accordingly to maintain the correct exposure. For example, if a scene will be correctly exposed at f/8 and 1/250 of a second at ISO 100, and you reduce the aperture size to f22, then you will need to set your shutter speed at 1/30 of a second or increase the ISO setting to 400 to achieve the same exposure. If adjustments to shutter speed and/or ISO aren’t made, you’ll run the risk of having an image that is too dark (underexposed) or too light (overexposed).

Challenge Activity

This challenge activity will help you master the art of depth of field. As in the sample image above, capture a scene that spans a great distance between the foreground and background. Use a minimal aperture (say, f/11-f/22) to create greater depth of field, and work on maintaining proper exposure by adjusting ISO and/or shutter speed settings.

Step 1: Find a scene with points of interest in the foreground, mid-ground, and background. A landscape is an ideal subject.

Step 2: Dial in a small aperture on your camera. Then, point the camera at the scene such that you frame the scene with the foreground and background elements in clear view. Focus on an object about 1/3 of the way into the scene, and press the shutter.

Step 3: Take a few photos at various angles and heights, noting each time the depth of field in each shot. Note as well that as lighting conditions change, you will need to make adjustments to the shutter speed and/or ISO to maintain a proper exposure.