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Aperture is the adjustable opening inside a lens that controls how much light reaches the camera sensor and helps determine how much of a scene appears in focus. A lower f-number means a wider opening; a higher f-number means a narrower one. Choose an aperture for the depth of field you want, then balance shutter speed and ISO for the exposure.
What aperture means on a camera
Aperture is the opening in a lens’s diaphragm through which light passes. It is described with an f-number, also called an f-stop. The scale can seem backward at first: a smaller f-number indicates a wider opening. For example, f/2.8 is wider than f/8 and lets in more light. A higher f-number indicates a smaller opening and less light. Nikon explains maximum aperture, and Sony defines aperture in its camera support material.
Aperture is both an exposure control and a creative choice. Changing it affects the amount of light available and the range of distances that appear acceptably sharp, known as depth of field.
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How aperture affects exposure
A wider aperture admits more light. If you want to keep the image’s brightness similar, you can compensate with a faster shutter speed or a lower ISO, depending on the scene and your other settings. A narrower aperture admits less light, which may call for a slower shutter speed or a higher ISO.
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Aperture, shutter speed, and ISO work together to determine exposure. The best adjustment depends on what you need to preserve: motion, depth of field, or low-noise image quality. Sony’s exposure-controls guide explains how the three settings relate.
How aperture changes depth of field
A wide aperture, such as f/2.8, tends to create a shallower depth of field: less of the scene is in focus, and the background may appear more blurred. A narrower aperture, such as f/8 or f/11, tends to increase depth of field so more of the scene can appear acceptably sharp.
Aperture is not the only factor. Focal length and focus distance also affect depth of field. Longer focal lengths and closer focusing tend to make it shallower, so the same f-number can produce different results in different compositions. Nikon’s depth-of-field guide describes these factors.
What aperture should you use?
For portraits
Try a wide aperture such as f/2.8 when you want to separate a person from the background. Check that the important parts of the subject are in focus. An especially shallow focus zone may not keep both eyes sharp, and it may be unsuitable for a group portrait. The right choice depends on the pose, distance, focal length, and how much of the subject needs to be sharp.
For landscapes
Start around f/8 or f/11 when you want more depth of field across a landscape. These are starting points, not guarantees: the scene’s depth, your focus distance, focal length, and the lens-camera combination all matter. Check the image at the size you intend to use it.
For low light or moving subjects
A wider aperture can provide more light and make it possible to use a faster shutter speed for a given exposure. That can help when light is limited or you need to reduce motion blur. The trade-off is shallower depth of field, so make sure the subject remains within the focused area.
When you need more of the scene in focus
Stop down until you have the depth of field your composition needs, then inspect fine detail at the intended output size. Do not assume the highest available f-number will always give the sharpest result: diffraction can soften detail at small apertures, and the point where that softness becomes visible varies with the camera and lens. Nikon’s diffraction guide explains the effect.
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When comparing settings or photographs, look beyond brightness. Ask what the aperture change did to each of these:
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- Depth of field: Did more of the scene become acceptably sharp, or did the background blur increase?
- Shutter speed: Did the exposure change allow a faster or slower shutter speed, and did that affect motion?
- ISO: Did you need to raise or lower ISO to maintain the desired brightness?
- Fine detail: Did stopping down help the scene’s depth of field, or did diffraction reduce apparent sharpness?
Choose the setting that supports your priority rather than treating one aperture as universally best.
Independent reader supportYour contribution helps us test, update, and keep practical guides available for everyone.What maximum aperture tells you about a lens
A lens’s maximum aperture is its widest available opening. It matters when you want more light or a shallower depth of field, but it does not determine the result on its own; focal length, focus distance, and the scene still matter.
Some zoom lenses have a maximum aperture that changes across the zoom range, while others maintain the same maximum aperture throughout. If you are comparing lenses, check the specification for the focal lengths you expect to use and confirm that the lens fits your camera mount. Changing the aperture setting on a compatible lens does not require buying a new lens.
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