Focusing and sharpness in photography

A sharp photograph starts with accurate focusing. However, blur can also be deliberately used as a creative effect. Technique and creativity together determine the final result.

Focusing

Autofocus systems use contrast and/or phase information to determine where the image is in focus. The camera then drives the lens to focus on the selected subject.

Autofocus

Modern cameras can focus automatically when the shutter button is pressed halfway or when a separate AF button is used. Depending on the camera and subject, several autofocus modes may be available.

• AF-S: the camera focuses once. Suitable for stationary subjects.
• AF-C: the camera continuously adjusts focus while the subject moves. Suitable for moving subjects.
• AF-A: on cameras that provide this mode, the camera automatically chooses between single and continuous autofocus.

Manual focusing

Manual focusing can be selected using the AF/MF or M/A/M switch on the lens or through the camera settings. Nikon lenses, for example, may use M/A and M, while Canon commonly uses AF and MF. This setting is separate from the M mode used for manual exposure.

Selecting focus points

Digital cameras have multiple focus points or focus areas that allow you to determine where in the frame the camera should focus.

The images show one and nine selected focus points in the viewfinder of a Nikon D7100. Depending on the camera, many more focus points or larger focus areas may be available.

The centre focus point is often used, but another focus point may be more practical for a different composition. Moving the focus point can reduce the need to recompose after focusing.

Preventing motion blur

Keeping the camera steady

Camera-induced motion blur occurs when the camera moves during the exposure. A tripod is a simple way to keep the camera stable. You can also use the self-timer or a wireless remote release to avoid moving the camera when pressing the shutter.

When the camera is mounted on a tripod, check the manufacturer's recommendations for image stabilisation or vibration reduction. Some systems can remain enabled, while others should be switched off. On a DSLR, mirror lock-up can also reduce vibration caused by the mirror mechanism.

Without a tripod, you can support the camera against a wall, fence, table or another stable surface. A simple form of stabilisation is also possible with a taut cord attached to the camera and held under your foot.

Using a faster shutter speed

A fast shutter speed reduces the risk of motion blur. For fast-moving subjects, such as in sports photography, shutter speeds of 1/1000 second or faster are often suitable for freezing movement.

When shooting handheld, the traditional starting point is a shutter speed approximately equal to the reciprocal of the focal length. At 80 mm on a full-frame camera, this means approximately 1/80 second. With a crop-sensor camera, a high-resolution sensor, a moving subject or no image stabilisation, a faster shutter speed may be necessary.

Depth of field and aperture

Depth of field is determined by factors including focusing distance, focal length, aperture and sensor format. Under otherwise equal conditions, a higher f-number such as f/11 provides greater depth of field than a lower f-number such as f/2.8.

Modern lenses usually no longer have a detailed depth-of-field scale. An app or online calculator can help calculate depth of field or hyperfocal distance.

Hyperfocal distance

The hyperfocal distance is the focusing distance at which depth of field, according to a chosen criterion of acceptable sharpness, extends from approximately half that distance to infinity.

A commonly used formula is: H = F²/(N × c) + F. F represents focal length, N the f-number and c the diameter of the permitted circle of confusion.

The calculated hyperfocal distance depends on factors including sensor format and the selected circle of confusion. An app or calculator is therefore usually the easiest way to determine the distance in practice.

Example: at a focal length of 35 mm, f/11 and a circle of confusion of 0.03 mm, the hyperfocal distance is approximately 3.7 metres. When focusing at this distance, the acceptably sharp area extends from approximately 1.85 metres to infinity.

Using blur creatively

Blur does not have to be a mistake. When used deliberately, it can add movement, speed, depth or atmosphere to a photograph and direct attention towards the main subject.

Panning

When panning, the camera follows a moving subject during the exposure. This can keep the subject relatively sharp while the camera movement renders the background blurred.

A shutter speed such as 1/60 second can be a good starting point, but the ideal shutter speed depends on the speed and distance of the subject. Follow the subject smoothly and take several photographs. Successful panning mainly requires practice.

The cyclist is relatively sharp while the background is blurred by the camera's panning movement. The scooter in the background reinforces the impression of speed.

Bokeh and shallow depth of field

Bokeh describes the character of the out-of-focus areas outside the plane of focus. It is often visible as soft, blurred points of light in the background. A wide aperture such as f/1.8 or f/2.8 can help create a shallow depth of field and a clearly blurred background.

Read more about Background and bokeh .

Slow shutter speeds and motion blur

A slow shutter speed can record movement as blur. Moving cars, for example, can create light trails, while flowing water can take on a soft, smooth appearance.

This effect can be used both in low light and during daylight. In bright conditions, an ND filter may be needed to achieve a sufficiently long shutter speed without overexposing the image.

This is not panning. The camera remains pointed at the scene while the car moves through the frame. The long exposure records the movement of the car as motion blur.