Getting the colour right can be the most difficult part of photo editing but a little knowledge of how the colours are made will make this much easier. On the right we have a ‘colour wheel’ to help illustrate the concepts that you need to grasp.
All colours are made from three primary colours – red, blue and green. Forget what you learned in Art at school we are now dealing with light not pigments.
Where the three colours overlap in the middle of the colour wheel we get a neutral grey (somewhere between black and white depending on the intensity of the colours). I have faked it here slightly for the purpose of illustration.
Where two of the colours overlap they form other colours known as ‘subtractive primary colours’. Another way of looking at it is that if you remove one colour from the middle of the wheel you will get a new colour. For example, if you remove red from grey you will be left with a mixture of blue and green, this colour is called ‘cyan’. If you remove or subtract green from neutral grey you are left with a mixture of red and blue known as ‘magenta’. Red and green combine to make the third ‘subtractive primary colour’ – yellow. Knowlege of these six colours and how they relate to each other will enable you to correct any colour cast in a picture.
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Introduction
Until a couple of years ago compact digital camera manufacturers were happy to admit that small, high resolution sensors lacked the sensitivity to offer high ISO modes – anything over ISO 400 was very rare indeed. This is unfortunate because there are many times when the ability to shoot in low light without flash is either essential or at the very least highly desirable. From low-light landscapes to atmospheric portraits to high speed sports there are endless situations where a higher sensitivity setting offers huge benefits (something SLR users take for granted).
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Faced with strong sunlight, the professional photographer will reach for his reflector. These actually fold up quite small for carrying around but not quite small enough to stick in your pocket on the summer holiday, also you need an assistant to hold it in place for you.
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It’s useful to know a little about the inverse square law especially when using flash or studio lights. Basically all the inverse square law says is that an object that is twice the distance from a point source of light will receive a quarter of the illumination. So what it means to us photographers is that if you move your subject from 3 metres away to six metres away, you will need four times the amount of light for the same exposure. This can most easily be achieved by opening the lens aperture two f-stops (see aperture for an explanation) or using a flashgun that is four times as powerful.
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