Switching a camera from automatic to manual mode can feel like a major step. Suddenly, instead of simply composing the photograph and pressing the shutter button, you are faced with numbers, dials and unfamiliar terms.
Aperture, shutter speed and ISO may initially appear technical, but each controls something straightforward. Aperture affects how much of the scene appears in focus. Shutter speed determines how movement is recorded. ISO helps you work in different lighting conditions.
Together, these three settings control the exposure—or overall brightness—of a photograph. More importantly, they give you creative control over how the finished image looks.
What is the exposure triangle?
Aperture, shutter speed and ISO are often described as the exposure triangle because they work together. If you change one setting, you may need to adjust another to maintain a similar level of brightness.
For example, imagine that you select a faster shutter speed to freeze a moving subject. Because the camera has less time to collect light, the resulting image may become darker. You could compensate by opening the aperture more widely or increasing the ISO.
This relationship is the central principle behind manual photography. As Nikon’s guide to exposure explains, the three elements are always linked, so choosing settings is a balancing act.
However, exposure is not only about making an image bright enough. Different combinations of aperture, shutter speed and ISO can produce photographs with similar brightness but very different visual characteristics.
“Manual mode becomes much less intimidating when you stop thinking of it as a collection of technical settings. Aperture controls the amount of light entering the camera and influences depth of field, shutter speed controls the duration of the exposure and can affect how motion is rendered, while ISO controls the camera sensor’s sensitivity to light and influences image noise. Together, these settings allow you to control exposure while making deliberate creative decisions about how you want the photograph to look and communicate.” — Ana Vieira de Castro, Photography Tutor
Aperture: controlling light and depth of field
Inside a camera lens is an adjustable opening called the aperture. It can widen to allow more light through the lens or narrow to reduce the amount of light entering the camera.
Aperture is measured in f-numbers or f-stops, such as f/2.8, f/4, f/8 and f/16. The numbering can seem counterintuitive at first:
- A small f-number, such as f/2.8, represents a wide aperture.
- A large f-number, such as f/16, represents a narrow aperture.
A wide aperture allows more light into the camera. This can be helpful when photographing in lower light or when you need to use a faster shutter speed.
A narrow aperture admits less light, so you may need a slower shutter speed or higher ISO to maintain the exposure.
Aperture also affects depth of field: the distance between the nearest and farthest parts of an image that appear acceptably sharp.
A wide aperture such as f/2.8 can produce a shallow depth of field. The subject may appear sharp while the background becomes attractively blurred. This technique is frequently used in portrait, wildlife, food and detail photography because it helps separate the subject from its surroundings.
A narrower aperture such as f/8 or f/11 generally creates greater depth of field. More of the scene appears in focus, making these settings useful starting points for landscapes, architecture and other photographs in which foreground and background detail are important.
Depth of field is also affected by focal length, focusing distance and sensor size, so aperture is not its only influence. Nevertheless, it is one of the photographer’s most important creative controls.
The simplest way to explore its effect is to photograph the same subject at several apertures while keeping the focus point unchanged. Look not only at the brightness but also at what happens to the background.
Shutter speed: deciding how movement will look
Shutter speed controls how long the camera records light. It is normally expressed in seconds or fractions of a second, such as 1 second, 1/30, 1/250 or 1/1000.
A fast shutter speed exposes the sensor for a very short time. It can freeze movement, making it useful when photographing sport, wildlife, children, vehicles or water droplets. Canon suggests that approximately 1/250 second may freeze a person walking, while faster subjects can require much shorter exposures. These are starting points rather than universal rules, because the required speed depends on the subject and how it is moving. Canon’s motion-photography guide provides further practical examples.
A slow shutter speed records the scene for longer. Anything moving during the exposure may appear blurred. Sometimes this is an unwanted consequence of camera shake, but it can also be used deliberately.
A slower shutter can turn moving water into a smooth stream, create trails from vehicle lights or communicate the energy of a busy street. Panning—moving the camera to follow a subject during the exposure—can keep the subject relatively sharp while creating directional blur in the background.
Because slower shutter speeds also record movement of the camera itself, a tripod or another stable support may be necessary. Image stabilisation can reduce the effects of camera movement, but it cannot freeze a subject that moves during the exposure.
Shutter speed therefore involves two connected questions: how much light does the camera need, and how do you want movement to appear?
“There is no single ‘correct’ shutter speed for a moving subject. A photographer might freeze a cyclist sharply or allow movement to blur and communicate speed. The better choice is the one that supports the intended story.” — Ana Vieira de Castro, Photography Tutor
ISO: responding to the available light
ISO controls how strongly the camera processes the signal captured by its sensor. For practical purposes, increasing ISO makes it possible to produce a brighter image without widening the aperture or slowing the shutter speed.
Common settings include ISO 100, 200, 400, 800, 1600 and higher.
A lower setting, such as ISO 100, usually delivers a cleaner image with greater detail and less visible noise. It is a natural choice in bright conditions or when the camera is supported and a longer exposure can be used.
A higher ISO can be useful indoors, after sunset or when photographing fast action. It might allow you to select a shutter speed fast enough to avoid blur when there is insufficient light for your preferred aperture.
The trade-off is image quality. As ISO rises, noise may become more visible, colours can become less accurate and fine detail may be reduced. How noticeable this is depends on the camera, exposure and viewing size.
This does not mean that high ISO should always be avoided. A sharp, expressive photograph with some noise is often more successful than a cleaner image that is blurred because the shutter speed was too slow. ISO is a practical tool, not simply a measure of image quality.
How the three settings work together
Suppose you are photographing a portrait outdoors.
You might begin with aperture because controlling the background is your priority. You select f/2.8 to create shallow depth of field. Next, you choose a shutter speed fast enough to avoid camera shake and capture small movements by the subject. Finally, you adjust ISO until the exposure is where you want it.
For a sporting event, you might make a different decision. Freezing action is now the priority, so you select the shutter speed first—perhaps 1/1000 second. You then choose an aperture that provides sufficient focus around the subject and raise the ISO if the available light is insufficient.
For a landscape, you might want considerable depth of field, so you choose f/8 or f/11. If the resulting shutter speed is too slow for handheld photography, you could use a tripod rather than increase ISO.
This is why there is rarely one perfect combination of settings. The photographer decides which visual quality matters most and then balances the remaining controls around it. Canon’s exposure guidance demonstrates how different combinations can achieve similar brightness while giving photographers different creative options.
Do you need to use full manual mode?
Learning manual settings does not mean you must use Manual mode for every photograph.
Aperture Priority—usually marked A or Av—allows you to select the aperture while the camera chooses an appropriate shutter speed. It is useful when depth of field is your main concern.
Shutter Priority—often S or Tv—lets you select the shutter speed while the camera controls the aperture. It is helpful when photographing movement.
Manual mode gives you direct control over both. You can still use Auto ISO if lighting conditions are changing quickly, allowing the camera to adjust ISO while you retain control of aperture and shutter speed.
These modes are not shortcuts that prevent learning. They are practical tools used by photographers according to the subject, conditions and degree of control required.
A simple manual-mode exercise
Choose a stationary subject near a window or outdoors in consistent light. Set the camera to Manual mode and begin at ISO 100 or 200.
First, change the aperture across several photographs and observe the effect on the background. Adjust the shutter speed each time to restore a similar exposure.
Next, keep the aperture fixed and photograph something moving at several shutter speeds. Compare where movement appears sharp and where it becomes blurred.
Finally, photograph the same scene at progressively higher ISO settings. Examine the images closely and notice when noise becomes visible on your camera.
“The quickest way to understand manual settings is to change one variable deliberately and study the result. Once you can predict what a setting will do, operating the camera begins to feel intuitive rather than technical.” — Ana Vieira de Castro, Photography Tutor
From correct exposure to creative intention
Automatic modes can produce well-exposed photographs, but they cannot always know whether you want to blur a waterfall, freeze a dancer or soften the background behind a portrait.
Understanding aperture, shutter speed and ISO allows you to make those decisions yourself. With practice, the numbers become less important than the visual questions behind them: How much should be in focus? How should movement appear? What balance between available light and image quality is appropriate?
Manual camera settings are not an obstacle between the photographer and the photograph. They are the tools that help turn an idea into an image.
Interested in developing your technical skills and creative approach? Explore our photography courses and discover how structured study can help you gain greater confidence behind the camera.
Ana Vieira de Castro, Photography Tutor
Ana Vieira de Castro is a photographer, visual artist, and educator whose work blends fashion, fine art, and curatorial practice. Ana holds a BA in Visual Arts and Photography and a Postgraduate Degree in Curatorial Studies. She has taught widely, curated major festivals, and exhibited internationally, including at EXPO 2025 Osaka.
