Digital Photography

Chapter 06
Shooting Tips
Aside from the pictures you miss because you forget to carry a camera, two factors are responsible for the majority of missed shots everyday photographers report. The first is the delay between when you press the shutter button on your digital camera and when the picture is actually taken. This is often referred to as 'shutter lag' but is actually a combination of shutter and autofocus lag. Our preferred term for this combination is 'capture lag'.

The second is blurring of pictures, which can be caused by two factors that may interact with each other: camera shake and subject movement. Both these problems can be minimised and, often, avoided.

Capture Lag
Three factors contribute to capture lag:

1. the time the camera's autofocusing system takes to lock onto the subject (known as 'autofocus lag' or 'AF lag');
2. the time the camera's exposure processing system takes to set the correct lens aperture and shutter speed for the shot (the actual 'shutter lag');
3. the use of red-eye reduction systems, which can delay shutter triggering.

In modern cameras, AF lag is usually longer than shutter lag - although the reverse was often true with early digital cameras. Lag times are often shorter in DSLR cameras than for digicams. When testing digital cameras for Photo Review Australia we have found lag times for digicams to be measurably longer than for DSLR cameras, with digicams averaging 0.4 seconds (although some cameras have lag times as long as one second) and DSLRs averaging around 0.1 seconds. The longest lag time we have measured for a DSLR camera was 0.5 seconds.

Overcoming capture lag on a digicam is relatively straightforward: turn off red-eye reduction and pre-focus the shot. However, pre-focusing only works when the subject is stationary so you need to estimate the distance for moving subjects and focus manually. Many DSLR cameras include focus tracking, which keeps the lens focused on a moving subject once focus has been achieved.

Shooting a burst of photos can also help you to ensure you have at least one sharp picture. As a general rule, subjects moving towards or away from the camera are easier to keep in focus than subjects passing across the field of view.

Sharp Shooting
Camera manufacturers have developed a number of technologies to help photographers take sharp pictures in more challenging situations. These include image stabilisation systems (see below) and improvements to the autofocus system that reduce the time the lens takes to focus.

Many cameras have AF-assist lights to help the autofocusing system lock on to dimly-lit subjects. Focus tracking (see above) can also help to ensure it remains sharp. Both these shooting aids tend to deplete the camera's battery. 

Some other tips for increasing the ratio of sharp pictures you take include:

1. Panning, in which you track a moving subject with your camera, pressing the shutter when the motion of the camera and subject are in synch. Backgrounds in the shot should appear blurred, while the subject is sharp. Slow shutter speeds (1/30 second or slower) are recommended for this shooting technique.
2. Increase the shutter speed - or select the Sports mode - to 'freeze' the action and obtain a sharp picture. You may need to increase the ISO setting to allow a faster shutter speed to be used.
3. Record a burst of shots using the continuous shooting mode. In most situations this should increase your chances of taking at least one sharp picture.

Subjects that May Increase Autofocus Lag
Focusing times are likely to be increased when you photograph certain types of subjects. Some examples are shown below.


Low contrast scenes that make it difficult for the autofocus system to find an edge to lock on to.


Subjects covering a wide range of distances. Where should the lens be focused?


Fast-moving subjects photographed in low light conditions with long telephoto lenses. The leaves nearer to the camera are de-focused due to use of a wide lens aperture, which reduces depth-of-field.


Subjects behind glass, mesh or bars. The camera's auto-focus system is likely to focus on the closest object, leaving the main subject unsharp.

Image Stabilisation
Also known as 'anti-shake' or 'anti-blur', image stabilisation can significantly increase your chances of taking sharp pictures if the right system is used. Three systems are currently popular:

* ISO-boosting or 'digital image stabilisation' simply increases the sensor's sensitivity, allowing the photographer to shoot at a faster shutter speed, thereby reducing the chance that camera or subject motion will produce blurring. Cameras that rely totally on this system can produce very noisy pictures in dim lighting. It is, therefore, the least effective of the three options, although it can address both camera and subject movement.

* 'CCD-shift' stabilisation combines sensors that detect camera motion with a compensatory mechanism that shifts the image sensor to counteract it. This system is popular in DSLR cameras and can allow photographers to use shutter speeds up to 2 to 3.5 f-stops slower than they could with an unstabilised camera. However, it only counteracts camera shake and can not compensate for subject motion.


In cameras with CCD-shift image stabilisation, the image sensor itself is moved to counteract camera movement.

* 'Lens-shift' or 'optical' image stabilisation uses similar motion detectors to the CCD-shift system but mounts them in the camera's lens and compensates for camera movement by shifting an element (or group of elements) in the lens. This type of system is also found in 'image stabilisation' or 'vibration reduction' lenses and is generally considered the most effective of the three systems, providing an a shooting advantage of up to four f-stops. Unfortunately, it cannot compensate for subject motion.


In cameras with lens-shift stabilisation, one lens element (or group of elements) is moved to counteract camera movement.

If your camera and/or lens don't have image stabilisation, one of the best ways to ensure blur-free shots in dim lighting is to mount the camera on a tripod and trigger the shutter with a remote trigger or the self-timer. Not only is the camera kept still while the shutter is open, but the delay in triggering the shutter also allows residual vibrations to subside.

In-Camera Processing Systems
Two in-camera image processing systems have become popular recently for correcting two common shooting faults: Face Detection AF and AE and Red-eye Removal. Both have become relatively common in the latest digicams and, although not really necessary for obtaining good pictures, they can provide some worthwhile benefits for novice photographers.

Face Detection AF and AE uses shape identification plus data from the camera's autofocus and auto exposure systems to fine-tune exposure levels and focus so that faces in the shot are sharp. Most systems are effective but not really necessary with small-sensor digicams, whose inherent depth-of-field is usually large enough to cover group shots of people.


Face Detection systems use shape identification to pick out faces in a scene. The camera's image processor will then fine-tune focusing and exposure levels to produce a sharp, correctly-exposed picture.

 
Most cameras with built-in red-eye correction use technology developed by Fotonation, which can detect more than 85% of affected shots and apply in-camera correction before they are recorded to the memory card.

Red-eye Removal is more of a convenience (or even novelty) than a necessity. Most cameras have red-eye reduction systems that fire a burst of light at the subject's eyes to close the iris before the flash is fired. Cameras with built-in red-eye removal processing can identify red eyes in flash shots and replace the red with black (or another dark tone). You can also correct red eyes in editing software using applications like Google's Picasa, which is straightforward and effective.

Neither of these shooting aids can overcome problems caused by poor shot composition (such as cut-off heads and inappropriate backgrounds) and they can't prevent people from closing their eyes in flash shots.

Pre-Set Scene Modes
Many cameras include a selection of 'scene' pre-sets that match the camera's exposure and focus controls to specific subject types. By understanding how the scene settings work, you will know when to use them - and how to use them to your advantage. The table below provides a guide to what the most common scene modes do and when to use them.

Scene Setting	What it Does	When to Use It
Portrait	Sets the lens to the telephoto position. Selects the widest practical lens aperture. Activates face detection. May enhance skin tones.	For differential focusing where you want to isolate a subject from a potentially distracting background.
Landscape	Sets the focus to infinity and stops the lens down. May increase sharpness and saturation and/or enhance blues and greens.	For distant subjects where maximum depth of field is required.
Sports	Selects a fast shutter speed and wide lens aperture. May set high ISO value and engage continuous shooting. Flash is activated if required.	For moving subjects.
Close-up	Selects macro focus. May also set high colour saturation.	For close subjects.
Portrait + Scene	Sets lens to wide angle and minimum aperture and focus to 2-3 metres. Activates face detection. May also enhance skin tones.	For closer subjects where maximum depth of field is required.
Night Scene	Sets slow shutter speed and daylight white balance. Turns flash off.	For low light shots where both close and distant detail must be captured and natural colours are required.
Night Portrait	Sets slow shutter speed and red-eye reduction flash. Activates face detection. May also enhance skin tones.	For shots of people after sundown, where a natural-looking balance between subject and background detail is required.
Beach	Increases exposure by between 1 and 2 f-stops.	For shots taken in very bright lighting where more than 50% of the area is covered by light-coloured sand.
Snow	Increases exposure by between 1 and 2 f-stops.	For snow scenes where more than 50% of the scene is snow-covered.
Party	Sets fast shutter speed and high ISO value. Activates face detection. May activate flash.	For capturing action in low light levels and under indoor lighting.
Fireworks	Sets lens focus to infinity. Selects very slow shutter speed. Turns flash off.	For fireworks and other distant bright subjects photographed after dark.
Museum	Turns flash off. Sets high ISO value. May activate burst mode to minimise the risk of camera shake.	For indoor situations where flash photography is forbidden.
Food	Sets lens to close focus. Selects high saturation.	For close-up shots that could benefit from enhanced colours.
Candlelight Portrait	Sets daylight white balance, high ISO value and low sharpness. Turns flash off. Activates face detection.	For indoor portraits in dim artificial lighting where warm colours are desirable.
Children	Selects fast shutter speeds.  Activates face detection. May enhance skin tones.	For action shots in variable lighting.
Pet	Selects fast shutter speeds. May set focus to telephoto position. May turn flash off.	For action shots in variable lighting where a good working distance is required.
Soft Focus	Selects low sharpness and slightly blurs focus. Activates face detection.	For 'glamour' portraits where skin blemishes must be minimised.
Text	Sets focus to macro range. Selects high sharpness and contrast.	For copying printed documents and signs.
Sunrise/Sunset	Sets focus to infinity. Selects daylight white balance. May add red filter.	For sunrises and sunsets where a red colour bias is desired.
Twilight	Selects high ISO value and high colour saturation. May add magenta filter.	For pre-dawn and twilight shots in which colour is an important feature.
Monochrome	Adjusts colour for black & white or sepia.	For 'old style' black and white or sepia toned pictures.
Natural Green	Selects high sharpness and saturation. Boosts green hues.	For shots of vegetation where maximum detail is required.
Soft Flowing Water	Sets a very slow shutter speed. (Tripod recommended.)	To blur out running water for a soft effect.
Splashing Water	Sets a very fast shutter speed. May activate flash.	To 'freeze' moving water. Can be used for shots of fountains, waterfalls and cascades.
Coupling Shot	Sets camera to capture two separate views by dividing the scene into left and right halves.	For taking a combined portrait of two people.
Pre-shot	Sets the camera to combine a background shot (captured first) with a shot of a subject (captured second).	For taking a portrait shot that positions the photographer in front of a background.
Backlight	Sets flash fill to counteract backlighting.	To illuminate the shaded side of a subject that is lit from behind.
Underwater	Adjusts colour balance to counteract loss of reds. May increase ISO value and/or activate flash.	For underwater photographs taken below 3 metres depth.