Exploring Aperture

Welcome to the first of the "Mastering Manual Mode" experiments where aperture control is the goal.

To understand how aperture impacts my photography, I will be conducting two different experiments. Before we jump into these experiments, let us first take a look at what aperture is and how it works.

What is aperture:

Aperture makes up one pillar of what is known as the exposure triangle. Aperture is adjusted in conjunction with the two other pillars, shutter speed and ISO, to produce a perfectly exposed photograph.

A camera's aperture is a controllable, circular, opening contained within the lens that restricts the amount of light that reaches the cameras sensor. Think of the iris of an eye. It opens and closes to control the amount of light that reaches the retina. In the case of a camera, the iris is the camera's sensor, but instead of a muscle, it is a set of overlapping blades.

Diagram 1

Aperture is usually denoted on a camera as an “F” followed by a number. For example, an aperture of 5.6 would be shown as F5.6. The higher the number the narrower the opening of the aperture. This can be seen in diagram 1.

On most DSLR and Mirrorless cameras, there are two ways to control the aperture. They are:

1.       Aperture priority mode: Denoted by AV or A, aperture priority mode leaves the shutter speed to be adjusted automatically by the camera along with ISO if desired. This mode is used when control of the aperture is desired.

2.       Manual mode: Usually denoted by M, this mode gives full control of all settings to the photographer.   

One thing to note is that different lenses have varying minimum and maximum aperture values. One 50mm prime lens might be able to reach a minimum aperture of F1.2 whilst another might only be able to achieve F2.8. The focal length also plays a part in the minimum and maximum aperture values, primarily due to the difficulties and costs involved in their manufacture.

Now that we know what aperture is, let's get out into the field to prove what it does.

Experiment 1: Exposure

Exposure in photography terms is the amount of light that reaches the sensor of a camera. This control of light is crucial in determining how bright or dark a photograph appears.

In this first experiment, I will show how changing the size of the aperture affects the exposure of a photograph. The camera that I will be using is a Fujifilm X-T5 with an XF33mm F1.4 R LM WR lens.

To keep the experiment as controlled as possible, I put my camera on a tripod and set it to manual mode. My manual settings were as follows:

• Shutter Speed: 1/125 Seconds

• ISO: 125

• Aperture: variable

I then proceeded to take several photos at different aperture settings. Here are the results:

Image 1 (ISO 125, Shutter speed: 1/125 seconds, Aperture: F1.4)

Image 2 (ISO 125, Shutter speed: 1/125 seconds, Aperture: F5.6)

Image 3 (ISO 125, Shutter speed: 1/125 seconds, Aperture: F16)

Image 1 was taken with the aperture wide open at F1.4, allowing maximum light to enter the lens and be absorbed by the sensor. As we can see, the highlights are blown out and the shadows are far too bright causing all details of the subject to be lost in a sea of white. This has left a vastly over exposed photograph.

In contrast, image 3 was taken with the aperture closed at F16, restricting the light to a minimum through the lens. This has left the photograph vastly under exposed. The shadows are far too dark along with the highlights. This has also caused the loss of details in the subject amongst the black.

Image 2 shows the same image taken with an aperture of F5.6. This aperture has produced a correctly exposed image due to all three main settings aperture, shutter speed and ISO being balanced to allow the perfect amount of light to reach the camera's sensor.

From these photos, we can clearly see how changing the size of the aperture affects the exposure of the photograph. By allowing more or less light to be absorbed by the sensor, we can change the overall exposure of a photograph. When looking at exposure, one should pay attention, not only to the subject, but also to how exposed the foreground and background is. This gives a good indication whether the image is correctly exposed. Although image 2 is correctly exposed, the foreground is a little under exposed. Therefore, depending on how important that is to the photographer’s vision for the photograph, they might make the decision to open the aperture to F4. In effect, somewhat brightening the foreground.

Experiment 2: Depth Of Field

Depth of field equates to the distance between the closest and farthest objects in a photograph that appear to be acceptably sharp or in focus. The higher the depth of field the higher the level of detail in a photograph.

Referring to Diagram 2, we can see that the wider the aperture, the shallower the depth of field. Conversely, the narrower the aperture the deeper the depth of field. We can also see the different tolerances for the subject to be in focus with differing aperture values.

Shooting tip: taking photographs with a small aperture is great, but the likelihood that you'll end up with an out of focus subject is higher. For instance, when taking portraits at F1.4 one has to be very selective with the camera's point of focus on the subject. The reason for this is that the depth of field can be as small as the distance between the eye and the tip of the nose. Therefore, it's essential that the camera's focus point is trained on the eyes. (Or at least one of them). As T Jefferson once said, “With Great Risk Comes Great Reward”

Diagram 2

In this second experiment, I will show how changing the size of the aperture affects the depth of field of a photograph. The camera that I will be using is a Fujifilm X-T5 with an XF33mm F1.4 R LM WR lens.

To keep the experiment as controlled as possible, I put my camera on a tripod and set it so that the aperture was the only setting that I changed. My settings were as follows:

• Shutter Speed: variable

• ISO: 125

• Aperture: variable

As you can see, both the aperture and the shutter speed were adjusted during this experiment. The shutter speed was being controlled automatically by the camera. This ensured that I achieved the correct exposure for each photograph by varying the components of the exposure triangle. Can you guess what would happen if I kept the shutter speed and ISO fixed? I would have conducted experiment 1 again.

On a side note, if I was shooting handheld, I would have chosen to vary the ISO once the shutter speed reached 1/60. At shutter speeds below 1/60, one introduces the risk of camera shake or blurriness due to camera movement by the hands.

Once I had set up the camera, I proceeded to take several photos at different aperture settings. Here are the results:

Image 4 (ISO 125, Shutter speed: 1/50 seconds, Aperture: F1.4)

Image 5 (ISO 125, Shutter speed: 3/10 seconds, Aperture: F5.6)

Image 6 (ISO 125, Shutter speed: 5/2 seconds, Aperture: F16)

Image 4 was taken with the aperture wide open at F1.4. We can clearly see that this has blurred the background and isolated the subject in the frame. This has a great effect upon portraits and images that have a specific subject that the photographer would like to draw the viewer's attention to.

Image 5 was taken with an aperture of F5.6. In this image we can see the background starting to come into focus with more details visible on the flower.

Image 6 was taken with the aperture fully closed at F16. Here we can see the background is even more in focus and the plant shows even more detail. This depth of field is particularly useful when taking landscape photographs as one requires everything in the foreground to the background to be in sharp focus.

Looking at the results of this experiment, we can clearly see what role aperture plays in isolating a subject from the background. The amount of "blurriness" in the background is also dependent on focal length of the lens used and the physical distance from the subject. It is also dependent on the distance of the subject from the background. The closer the subject is to the background the more in focus the background will be. This is because the background is closer to the focal point of the lens.

Shooting tip: Lower apertures that create a shallow depth of field are desirable for portrait shooting. If you refer back to Image 4, you'll notice how shallow the depth of field is. The front of the plant is out of focus as is the rear of the plant. When taking a portrait, this has the effect of softening the skin making for a more pleasing photograph.

This concludes the aperture experiments for this blog. I hope that they help explain what the function of the aperture is, how it works and how to apply it to photographs in the hopes of improving and being more creative. In the next blog I will conduct two more experiments that explore another component of the exposure triangle. Shutter speed.