Digital SLR

Having selected the appropriate metering pattern, the next step is to choose the correct exposure mode and decide whether to rely on the camera's auto exposure (AE) system or manual controls. The main tool for engaging these settings is the mode dial.

Setting the mode dial to Auto puts the camera into 'point-and-shoot' mode, effectively handing over most controls to the camera's microprocessor. The camera sets the lens aperture, shutter speed, ISO and white balance to match the requirements of the scene it's pointed at. This mode is never found on professional cameras.
 

The Shutter-priority(S) mode is useful for 'freezing' fast action. (160mm focal length, ISO 1600, 1/197 second at f/3.2)

In 'P' mode, the camera also determines optimal aperture and shutter speed settings for the subject. But whereas the Auto mode limits the controls the photographer can access, the P mode in most cameras lets them change either aperture or shutter speed and will adjust the other parameter to produce the same exposure level. (This adjustment is known as 'program shift' or 'flexible program'.)

Whereas few settings are adjustable in the Auto mode, in P mode, the photographer can adjust the ISO and white balance settings and use manual focusing. Other adjustments normally blocked in full Auto mode include selection of metering patterns, exposure bracketing, continuous shooting, custom functions, colour space selection and some flash settings.

In 'A' and 'S' modes the photographer sets the aperture (A) or shutter speed (S or Tv in some cameras) and the camera adjusts the other parameter accordingly. The A mode is often used to control depth of field; large apertures produce shallow depth of field, while small apertures make everything sharp from close to the camera to the horizon.

The S mode is used to freeze action or produce intentional blurring in shots of moving subjects. Select fast shutter speeds to freeze action, as shown in the illustration to the left. Slow shutter speeds can be used to 'liquefy' flowing water, as shown below.


Flowing water photographed with a shutter speed of 1/1000 second at f/7.1, showing the effect of 'freezing' the motion of the water.


The same subject photographed with a shutter speed of 1/6 second at f/18.

Manual ('M') mode gives photographers full control over both aperture and shutter speed. The A, S and M modes provide full access to all camera settings (except exposure compensation in M mode).

Camera manufacturers have differing approaches to mode dial design, some of which are shown below.

The mode dials on Canon's entry-level and pro-sumer DSLRs are split into two zones: the Basic Zone containing the Auto setting (green rectangle) and the various scene pre-sets and the Creative Zone with the P, Tv (shutter priority), Av (aperture priority) and M settings. Canon adds an 'A-DEP' shooting mode, which sets the camera to record a wide depth of field in the shot. The camera uses data from nine AF sensor points to determine the nearest and most distant parts of the subject then selects a lens aperture that ensures they will be sharply imaged. This mode is handy for landscapes and group shots.



The mode dial on Nikon's entry-level DSLRs uses a grey background to distinguish between the P, A, S and M shooting modes and the Auto mode and scene pre-sets.



The latest Pentax DSLRs include two additional modes: a dedicated 'Sv' mode that prioritises ISO settings and enables the camera to adjust other parameters automatically and a 'TAv' mode, which lets photographers set both the aperture and shutter speed while the camera will adjust the ISO setting. The User mode denotes a custom memory bank where photographers can store groups of camera settings. The B setting is for Bulb exposures in which the shutter remains open as long as the shutter release is held down. The three icons below the mode dial are for metering pattern settings.



The mode dial on Sony's A200 and A350 models are identical and contain the standard Auto, P, A, S and M shooting modes and a selection of frequently-used scene pre-sets. Use of icons for the scene modes is the only distinction between them and the P, A, S and M settings.



Scene Pre-sets
Entry-level DSLRs (and some 'pro-sumer' models) provide a variety of pre-set 'scene' modes that help novice users to choose the appropriate camera settings for different subject types. The most common scene mode settings are portrait, landscape, sports, close-up and night portrait. Other modes may include: fireworks, sunset/sunrise, night scene, beach & snow, children & pets, candlelight and document/text.

Interestingly, the adjustments used by one manufacturer may not be the same as those used by another - although they will be similar for the same scene type. Cameras from the same manufacturer may also vary when new models are introduced.

The table above shows how the more popular scene modes work and when to use them. Use them with discretion because some of the subsidiary adjustments (such as increasing saturation or boosting blue and green) may not be appropriate for your subject.



Image Tone Adjustments
Most DSLRs have a special set of 'picture styles' that enable users to fine-tune the sharpness, contrast, colour saturation and colour 'tone' (or hue) settings in their digital images before shooting. As a rule, these controls can only be used in the P, A, S and M shooting modes. Up to five levels of adjustment are provided for each parameter and some cameras can 'memorise' up to three sets of parameter adjustments and store them in Custom memory banks for future use.

Sharpness adjustments work mainly on edges and allow photographers to sharpen or 'soften' their shots. Contrast and saturation (colour vividness) adjustments are similar, with the minus settings reducing and the plus settings increasing the selected parameter.

Colour tone adjustments are used mainly for tweaking the camera's colour reproduction system to produce better-looking skin tones. The minus settings in this parameter make skin tones a little redder, while the plus settings bias them more towards yellow.






The pictures above show the effect of sharpness adjustments. The top image is the original photograph, while an enlarged section of a sharpened version of the image can be seen in the middle image and a softened version immediately above. (Adjustments have been exaggerated to demonstrate the effects of each setting.) 

Canon's Picture Style system is a variant of parameter adjustments, which allows photographers to match image colour and tonal reproduction to certain requirements.

The table below shows the adjustments made to saturation and sharpness in each of the Picture Style settings.



The Monochrome setting has been designed specifically for recording B&W or sepia-toned pictures. Raw images captured with this setting can be converted back to colour with the bundled software - although JPEGs can not.


The Monochrome setting discards colour information when it is used for shooting JPEGS.

The main problem with all parameter adjustments is that the adjusted settings are locked into the image file (unless you shoot raw files). The adjustment range is also somewhat limited, compared with the adjustments available in image editing software - including raw file converters. For this reason, we advise photographers to use these in-camera controls judiciously.

It is usually better to make most of these adjustments on your personal computer. The computer's processing system is much more powerful than your camera's microprocessor. Your monitor is also much larger and more colour accurate so it's easier to be discerning when tweaking image files. Finally, if you don't like the changes you have made, it's easy to go back to your original (unadjusted) image and start again.

Custom Functions
Further extending the ability for photographers to customise their cameras, almost all DSLRs include one or more Custom memory banks where a large number of pre-determined camera settings are stored. Settings in these memory banks let you choose from a range of options or make selective adjustments to a particular control or shooting parameter. A typical entry-level DSLR may have as many as 20 separate settings that are controllable through the Custom Function, while a professional DSLR will have 60 or more.

Parameters that can be adjusted in the Custom Function menu include allocating particular button controls to adjust settings like image size and quality, exposure compensation, image tone pre-set, exposure or flash adjustment, autofocus mode, or AF point selection. The Custom Function menu can also be used to switch noise reduction on and off and/or control the level of noise reduction processing.

Other Custom Functions may include controlling the flash synchronisation speed, AE and AF lock functions, AF assist beam, flash metering, shutter curtain synchronisation for flash shots and exposure level increments (1/3, ½ or 1EV steps). Mechanical controls like mirror lock-up (for sensor cleaning or very long exposures), are usually covered in the Custom Function menu as well, along with power management and LCD display settings.

Some cameras also include bracketing settings for exposure, focusing and white balance in the Custom Function menu. Extension of the ISO sensitivity range may also be provided. Other cameras provide controls for matching the image sensor and processing control to a selected lens. For professional DSLRs that accept interchangeable focusing screens, the correct Custom Function must be set to match the exposure correction to the screen in use.

It is worth reading through your camera's instruction manual to see which functions can be adjusted through the Custom Function menu. Check the default settings to ensure the camera is adjusted to meet your own requirements before you embark on a shoot.

Colour Space Settings
The colour space setting on a digital camera delineates the range of colours it can reproduce. The default setting on all digital cameras is sRGB, which covers the colours that can be displayed on a computer or TV monitor. Most enthusiast and all professional DSLRs offer an additional colour space setting, known as Adobe RGB, which can record a wider range of hues and tones.

Landscape photographers who plan to print their best shots usually find the Adobe RGB setting gives them more colour information to work with and produces prints with a wider colour and tonal range. It's also suitable for photographers who like to shoot raw files and edit them before making prints. However, it's less relevant for portraiture and images captured with this colour space setting may look a little flat on many computer monitors. Many entry-level and multi-function printers can't reproduce all the Adobe RGB tones.

The default sRGB colour space setting will generally give the best results for most normal photography, especially shots of people. It should also be used for shots that are destined for online applications (emails and websites) and photos that will be displayed on a TV screen.

 USEFUL URLs
The following websites provide additional information on the topics covered in this article. 
en.wikipedia.org/wiki/Shutter_speed provides useful general information on shutter speeds.
en.wikipedia.org/wiki/F-number provides complementary information on lens apertures.
web.canon.jp/imaging/enjoydslr/index.html is an online tutorial covering shooting with a DSLR camera.