Starting off with your DSLR
STEP OFF THE GREEN SQUARE! Taking control…
As the photographer – the picture taker – deciding what to take a picture of is your very own, personal decision and so it makes perfect sense to be in control of how the picture looks. OK then, this is how:
Firstly – photography starts in your head: get a picture in mind, think about what should be in the image and how to get it there and then use these tools:
- Composition. Describes what visual elements are contained within the picture space or frame. E.g. subject, foreground, background, and the manner in which they are arranged.
- Focal Length. This is the actual length of the lens arrangement in mm (for a single element lens. Lenses today are multi-element devices and so focal length stated is a bit different to actual). Focal length determines how greatly the subject is magnified. Focal length will also affect the angle of view. The human eye sees in the range 35 – 50mm: longer than this and the lens is called a telephoto lens. Less than 35mm and the lens is called a wide-angle lens.
- Focus. This refers to the control of the plane in which the picture is at its sharpest. Focus is achieved by moving the elements in the lens relative to each other until the light from the subject is focused precisely on the camera sensor.
- Aperture. The aperture is hole within the lens that can be varied in size to alter the amount of light reaching the sensor. Large apertures allow lots of light through, but make for a shallow depth of field. Vice versa is also true. Aperture is measured as a fraction of the focal length. So f/4 is a bigger opening than f/32. Focus is only achieved in a flat plane, but depth of field refers to the rate at which clarity changes with distance from this plane, in front and behind it.
- Shutter. This is the curtain that starts and ends the exposure of the sensor to light arriving through the lens. Slow shutter speeds allow a lot more light to reach the sensor than do fast shutter speeds. Fast shutter speeds can “freeze” action and movement and thereby lead to a sharper image.
- Exposure. This refers to the amount of light captured in an image relative to that illuminating the subject or scene. Hence the twrms over- or under-exposed. (Image vs actual).
- Modes. These are simply pre-selected arrangements of some of the parameters above combined with some extra settings including exposure modes.
- Exposure Modes. Most pictures have a subject within a picture space. The exposure modes on a digital camera allow the user to determine which part of the image has priority when the camera computes the exposure.
Taking a digital image is all about capturing light in a given composition. Imagine the pixels on the sensor are a massive 1 Million-dozen egg box. When you open up the egg box the sensor is the array of cavities that the eggs sit in. Take the eggs out! Now the cavities, or pixels, are empty.
Firstly if we don’t put any light in the pixel it stays black – and you have a dark black, empty, picture.
In contrast, if you fill all the egg-box-cavity-pixels up completely they will go completely white – like a sheet of paper. Not that interesting either, unless you are into modern art.
A Histogram is a bar graph with black on the left and white on the right, and we want our image (in general) to have only a few empty (black) pixels and handful of full (white) ones. The rest we want as a spread of grey. The camera uses coloured filters to work out the RGB (Red, Green, Blue) balance and applies that to the final image using software – turning a grey/black/white image into a coloured one. Look at the histogram on your camera – it is very useful. A good histogram is usually evenly spread out and showing a good spread of tones stretching from left to right.
There are a handful of tools on the camera for controlling the exposure of the sensor. I.e. filling the pixels:
- The shutter (speed)
- The aperture (size)
- The ISO setting (sensitivity)
- Flash duration (amount and speed of light)
The Shutter is a curtain that opens to allow light to hit the sensor and closes to turn the light off. The longer the shutter is open the more light passes through it. Fairly obvious, but the shutter speed will also have a major effect on the image quality if it is too slow and the camera is unstable.
The Aperture is the hole in the lens through which light must pass to reach the shutter and then the sensor. The smaller the aperture the less light can pass through it –like turning a tap off reduces the flow of water. The aperture (expressed as a fraction of the focal length of the lens) also has an impact on the Depth of Field and the quality of the out of focus areas (called bokeh).
The ISO setting of the sensor determines the sensitivity of the pixels. A low ISO requires a lot of light to fill a pixel and vice versa. So ISO is used as an assistant to shutter speed. High ISO allow fast shutter speeds, but ISO setting also has an impact on image quality as high ISO can lead to increased image noise, usually seen in darker areas of an image.
Flash duration is used in combination with the shutter to manage the exposure of the sensor to light. The light flash – on sophisticated flash guns – can be regulated in time and intensity. Flash is also used to alter the appearance of an image or subject.
So that is all there is to it – get to know your camera and of course practice, practice, practice!
A mantra to remember:
Subject, Focus, Exposure, Composition:
Subject: The eye-catching part of your image.
Focus: The art of getting the subject, or part of the subject, crisply outlined so it is pleasing to look at.
Exposure: Ensuring the image is correctly lit for what you are trying to portray.
Composition: The arrangement of the subject(s) within the picture space and the elimination of distractions such that the resultant image is pleasing to the viewer.
Discuss: The Rule of Thirds, The Golden Ratio, The golden Triangle etc
It is often said photography is the art of exclusion which requires the photographer to work at eliminating unsightly distractions from an image, whilst painting is the art of inclusion where the painter decides what to add to the canvas.
Either way, thinking about the image and altering your point of view before taking it will help your composition. Unless of course it is a once-in-a-lifetime event, when you don’t want to be hanging about waiting to discover your creative streak!