Aperture is one of the central components of exposure. The aperture setting introduce physical and creative considerations for the photographer. For example, changing the aperture from f/2 to f/8 will alter the amount of light entering an sensor and the amount of the scene that is in focus.
Additionally, the aperture will determine the focus of the background for the subject. Understanding the various functions of each aperture will allow the photographer to make deliberate choice for each photograph rather than making random choices. The f-stop scale depict the range of apertures from the largest to the smallest opening.
How Aperture Affects Light and Focus
The f-stop scale also depicts the change in the amount of light that enters the sensor as the aperture stops open or close. When the aperture stops close, the amount of light that enters the sensor halve. At the same time, the depth of field increases.
The opposite is also true. If the aperture open, the sensor receive more light. At the same time, the depth of field decrease.
The f-stop scale allows the photographer to see the relationship between these factor for the photograph. Many cameras allow the aperture to change in one-third stop increments rather than full stops. These increments allow for more precision with the aperture adjustment.
Intermediate apertures allow the photographer to have a small depth of field while still maintaining the light that enters the sensor from a full stop of light. For example, sometimes reducing the highlights in a photo might also reduce the shutter speed. A third stop increment allow for such precision in adjusting the aperture.
Whereas f-stops are used in most photography, cinema lens use a different scale called the T-stop scale. T-stops indicate the amount of light that leave the lens rather than the aperture. While the two stops are usually similar, they might differ if the lens change during the shot.
If the depth of field is to remain the same, if any factor that alter the depth of field is changed, then the aperture must be changed. The focal length and the distance to the focused subject also manipulate the depth of field. A 50mm lens at f/1.8 will have a different depth of field than a 50mm lens at f/8. The longer the focal length, the more shallower the depth of field.
The wider the aperture, the shallower the depth of field. The shorter the focal length, the deeper the depth of field. The smaller the aperture, the deeper the depth of field.
If any factor other than the aperture is changed, the shutter speed should also be changed to maintain the same exposure. For instance, if the aperture is stopped down two stops, the shutter speed must also be changed two stops to maintain the same amount of light on the sensor. This is part of the exposure triangle.
To increase the depth of field, either the ISO or the shutter speed must be changed. The lenses are often most in focus in the middle of the aperture rather than at the maximum aperture. Many lenses reach their best sharpness if the aperture is stopped down two or three stops from the maximum aperture.
This is due to the fact that aberrations in the lens is strongest at the maximum aperture. The aberrations are strongest at the maximum aperture. As the aperture stops down, the aberrations decrease.
However, if the aperture is stopped down too much, the problem of diffraction can set in. Most lenses reach their sharpest focus at apertures such as f/5.6 or f/8.
The quality of the bokeh can change when the aperture change. Bokeh is the quality of the light coming from the lens that is not on the subject.
With wide aperture, the bokeh is large and round, which allows subjects to stand out from the background. When the aperture stops down, the quality of the bokeh change to the shape of the aperture. With apertures like f/11, the background may have too much detail relative to the subject.
However, with apertures like f/11, a sunstar effect may begin to show in the background. Different subject of a photograph will require different apertures. The aperture that works for one subject might not work for another subject.
For instance, portraits will use wider aperture to help focus on the subject. Landscapes will use a medium aperture setting because this will produce the highest level of sharpness in the photo. Sports photography will use wide apertures so that the shutter speed can be high.
For macro photography, smaller apertures will produce the depth of field required to focus on the object in close proximity. The sensor size and resolution will affect the visibility of diffraction. High-resolution sensors with small pixel will produce diffraction more easily than low-resolution sensors.
For instance, a 24-megapixel sensor might allow for f/11 without diffraction becoming a problem, but a 61-megapixel sensor might experience diffraction at f/8. The sensor is the factor that will change the visibility of diffraction, but the underlying concept of diffraction remains the same. An aperture chart allow photographers to understand the consequence of each aperture setting. By understanding how light, depth of field, sharpness, and bokeh change with the aperture, the photographer can use the aperture as part of the exposure to create the desired result in each photograph.
Using the aperture as part of the exposure allows the photographer to produce the same result in each photograph.