Photographic Principles

The shutter is the device that allows light to pass for a determined period of time, for the purpose of exposing photographic film (or imaging sensor in a digital camera) to the right amount of light, to create a permanent image of a view.

Shutter speed is the time for which the shutter is held open during the taking of a photograph to allow light to reach the film (or imaging sensor). The time a shutter remains open, is called the exposure time.

To achieve the correct balance of light in a photograph a photographer or the automatic modes on the camera must control the exposure time and the lens aperture setting. Together, these settings determine how much light reaches the film (or imaging sensor). Additionally, the exposure time must be sufficient to minimise the effects of camera shake and motion-blur of the subject. For a given exposure, a fast shutter speed demands a larger aperture to avoid under-exposure, just as a slow shutter speed is offset by a very small aperture to avoid over-exposure. Long shutter speeds are often used in low light conditions, such as at night.

Most shutters also generate a signal to trigger a flash, if connected.

Shutter speed is measured in seconds. A typical shutter speed for photographs taken in sunlight is 1/125th of a second. In addition to its effect on exposure, shutter speed changes the way movement appears in the picture. Very short shutter speeds are used to freeze fast-moving subjects, for example at sporting events. Very long shutter speeds are used to intentionally blur a moving subject or to blur the background using panning, for artistic effect.

Whilst on the subject of Shutters, we must mention Shutter Lag. This term simply refers to the time between taken for the camera to respond and take the picture after the shutter button is pressed. Shutter lag-time varies greatly from camera to camera with the more expensive SLR cameras having much less lag than the point and shoot compact camera models. Shutter lag is very annoying to the photographer wanting to capture people or animals on the move and is an excellent reason to purchase a Digital SLR camera which is much quicker at focusing. Look for a camera with a shutter lag of less than 0.5 seconds and learn how to prefocus to reduce the problem. This is because shutter lag is exacerbated by the time the camera takes to focus on the subject.

The aperture of a photographic lens can be adjusted to control the amount of light reaching the film or image sensor. The aperture itself is a hole or an opening through which light is admitted. Look down your camera lens and you'll see a curtain-like device (called the diaphragm). The diaphragm forms an aperture (opening) and functions much like the iris of the eye—it controls the effective diameter of the lens opening. Reducing the aperture size increases the depth of field, (the extent to which subject matter lying closer than or farther from the actual plane of focus appears sharp). In general, the smaller the aperture (the larger the number), the greater the distance from the plane of focus the subject matter may be while still appearing in focus.

In combination with variation of shutter speed, the aperture will regulate the film's degree of exposure to light. As already mentioned in the section on Shutters, a fast shutter speed will typically require a larger aperture to ensure sufficient light exposure, and a slow shutter speed will require a smaller aperture to avoid excessive exposure. In the example photos shown above of the waterfall - the photo on the right with the faster shutter speed is also darker - at 1/350 sec, the aperture was f/4.5, while in the photo on the left with the slower shutter speed more light was able to penetrate with the f stop closed down to f/13.

The lens aperture is usually specified as an f-number, the ratio of focal length to effective aperture diameter. A lens typically has a set of marked "f-stops" that the f-number can be set to. A smaller f-number denotes a larger aperture opening which allows more light to reach the film or image sensor.

Aperture Priority refers to a shooting mode used in most semi-automatic cameras. It allows the photographer to choose an aperture setting and allow the camera to decide the correct shutter speed.

When you get to know how important aperture is to photography, you'll start to appreciate why professional photographers have so many lenses, and why there is a big variation in the price of lenses. The specifications for a given lens typically include the minimum and maximum apertures. These refer to the maximum and minimum f-numbers the lens allows, respectively. The maximum aperture tends to be of most interest and is always included when describing a lens (e.g., 100-400mm f/5.6, or 70-200mm f/2.8). Lenses supporting large apertures (for instance f/2.8 – remember, smaller the number, the larger the aperture), are often called “fast” lenses because they allow faster shutter speeds to be used for the required exposure. "Fast" lenses are valuable as they allow much more light to reach the film and therefore reduce the required exposure time, thus improving photo quality when in low light, or of fast moving action.

The selection of a quality lens is one area that makes a huge difference in photography and what you get is determined by how much you pay. Despite digital components coming down in price significantly, the laws of optics and the costs of producing high quality optical components for the lenses has not really changed at all.

Surprisingly, the middle of a sunny day is rarely the best time to take a photograph. If this statement comes as a surprise to you, then read this section carefully and take some time to read more on this subject to improve your understanding of the effect of light on photography.

Firstly, let's talk about natural light as we're assuming your interest in photography whilst travelling will often be outdoor scenes. Obviously, we cannot change the weather, but any kind of weather is suitable for picture taking and the worst weather may actually suit your subject best. The trick is to compose your picture by understanding the weather, learning to read the natural lighting, and the position of light in your photo. One of the greatest advantages of digital cameras is the ability to preview the photo you've just taken so you always have a chance to see if you've got something wrong before leaving the scene. Good photographers often take various photos of the same scene, each time changing the viewpoint or settings to alter the use of light. Consider the following light issues every time you aim your camera:

• Bright sunny days bring out the colours of a scene to the eye but to the unskilled photographer can create washed out photographs, and also great areas of contrast with harsh dark shadows, and extremely bright areas. Very high sunlight will create shadows on people's faces or may cause your subject to squint. A flash, when used as the only source of light, will also create hard light with bright subjects against dark backgrounds. In this sort of situation the quality of light affects the mood of the picture so use the dark shadows as design elements or soften them with fill flash.



• Overcast days are often preferable for portraits (photos of people), as there are no harsh shadows under eyes, nose and chins. Flowers are also best photographed on cloudy days. The soft light of a cloudy day is actually very friendly to novice photographers and to semi-automatic cameras, with few shadows to confuse your auto-settings. Of course with the lower light conditions, slower shutter speeds will be required, so wind motion can become a problem.

One of the biggest issues for travellers is timing. All light has colour, and early or late in the day, sunlight has a soft warm golden glow, sometimes emphasised by dusty atmospheric conditions. Since the Australian outback is best depicted by earthy red glows, this warm glow tends to show off most natural forms to their best advantage and you'll be rewarded with quality photographs if you take the time to be on location in the early or late hours. Obviously, this may affect your travel plans so wise photographers get involved in the travel plan. Why not select some photographic highlights that you know will be best achieved in the early/late hours and work out your daily driving plan to ensure you do not upset the rest of your travelling party by wanting to stay on to get "the perfect photo", when everyone else is wanting to push on to get a hot shower at the caravan park just 50km away. Taking advantage of “first light” – even before dawn, and the few moments around sunrise provides beautiful light conditions – this can mean getting up before anyone else is up, but will make fitting your photography passion into the travel schedule easier.

When it comes to the direction of light, there are 360 degrees of possibilities. When the light isn't working for you, change it by moving your position or your subject's position, or the light itself, if possible. Sometimes waiting for the right light is an option, or noting how the light might be at some other time of day, and then coming back at that time for the photography.

The reason everyone positions people in outdoor photos to look into the sunlight is to remove shadows from faces but this is just a method of moving the subject to achieve front lighting. Learning how to use flash will improve your control of front lighting and with practise you'll use it in many situations including daytime photography, and especially in portrait photography. Other techniques including putting the subject near a source of reflected light.

Side lighting is perfect when you want to emphasize texture, dimension, shapes or patterns. Side lighting sculpts a subject, revealing contours and textures. Use side lighting to exaggerate dimension an depth. At a 45-degree angle to the side, its one the most flattering types of portrait lighting.

Light that comes from behind your subject is by far the most difficult to use. Taking a photograph that is backlit means that direct light is reaching your camera's light sensor so any auto program will reduce the aperture, resulting in less light reaching the foreground of your picture. If you have placed a person in the foreground, such as a person in front of the sunset scene, the result will be a silhouette of their body outline. If that's not your intent, then you'll need to provide some sort of front or side lighting. Many digital cameras will have a backlight compensation button (or learn to use exposure compensation) that will help in this situation to properly exposure your subject, but you may end up washing out the background and lose the soft sunlight glow. Using fill flash in this situation is usually the ideal - as this will give your portrait a glowing "halo" of rim light and prevents the silhouette effect.

In the days before digital, you would buy film in different settings of "speed". Typical print film ratings were 100asa, 200asa, 400asa. In simple terms, changing the type of film enabled photographers to alter their camera's sensitivity to light, with the higher numbers of film rating (eg. 200, 400) being better suited to lower-light situations, and 100 being better for outdoor, sunny conditions.

These days, with digital cameras, we can change the ISO setting instead. And of course, we have full control over the ISO/ASA for every photo, rather than having a whole roll of film at a particular ASA.

ISO settings have some limitations for use in that the higher the setting the grainier the look of the picture quality.

The main point here is that ISO is a tool you can use to make sure you get the right shot. It is just as important as shutter speed, and aperture.