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A light source that contains a mixture of all wavelengths of the visible spectrum.
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Artificial light appears in a variety of forms - tungsten and fluorescent being two of the most widely used. Each type of lighting produces a different colour temperature that our brain compensates for to make everything appear as though it's neutral light. Digital cameras and film are not so forgiving and record the colour as it really is, so in tungsten light the picture comes out orange/yellow and fluorescent goes green. These colour casts can be corrected using filters on a film based camera, and digital cameras have a white balance setting to make the pictures look like the view our eyes see. Some models have manual white balance control where you select the type of lighting from a list, but most take care of the colour automatically.
The colour created when one of the three red, green or blue primaries is taken away from white light. Complementary colours are cyan, magenta or yellow and are also known as secondary colours.
Used in colour printing where various amounts of cyan, magenta and yellow filtration are placed over white light to subtract unwanted quantities of red, green or blue.
Chromatic aberration, also called "colour fringing" or "purple fringing", is caused by a lens not focusing different wavelengths of light onto the precise same focal plane and/or by a lens rendering a different magnification each of different wavelengths. These two different types of chromatic aberration can both occur in one and the same image. Chromatic aberration can be seen as colour fringing around the boundaries that separate dark and bright parts of the image. It most frequently occurs around the edges of the image, especially in wide angle shots. Despite begin called "colour fringing" or "purple fringing", chromatic aberration can also affect black and white photography. Although a black and white image obviously has no colours in it, chromatic aberration can blur the image.
Reciprocity law states that as you increase the intensity of light reaching the film you also need to decrease the speed it reaches the film by the equivalent amount. Most films work quite happily between exposures of 1/2sec and 1/1000sec, but go beyond these extremes with a very low intensity of light and a long exposure or a very high intensity of light and a correspondingly short exposure and the law fails an exposure increase may be required when the shutter speed is beyond these limits. At these extremes the law fails. Compensation is required to adjust for this, but there is no strict rule to correct the error. Most film and paper manufacturers provide technical details on request with a rough guide to exposure adjustments. As a rough guide for an exposure of one second you would increase the speed to two seconds, or open the aperture by one stop. A speed of 10sec would need to be increased to about 50sec or open the aperture up two stops. With black & white film you only have to worry about this exposure correction, but with colour film does not only suffer from exposure problems but also colour casts. A colour film is made up of three individual colour layers, each layer suffers from reciprocity failure at different levels. On an uncorrected film the shadows may have a magenta colour cast but the highlights may suffer from a cyan cast. To correct the cast not only would a longer exposure be needed but also the inclusion of a colour correction filter of a low value, care would have to be taken in choosing the correct filter otherwise an over corrected result may appear.
A filtered light thats used in a darkroom to allow you to see while handling light sensitive material. Orange is used for most black & white materials, red for ortho, brown for variable contrast papers and a very deep green for colour materials.
Black & white printing paper that changes contrast when exposed to different coloured light. A yellow filtered light produces lower contrast, while magenta increases contrast.
The three additive colours that mixed in digital imaging to create the large range of colours. Overlapping these colours in varying strengths creates cyan, yellow and magenta while equal proportions creates white. Computer monitors create accurate colour by firing light through red green and blue phosphors while digital cameras and scanners use RGB filters over the CCDs to create the colour information.
A colourless filter thats used to absorb UV light and reduce haze when shooting with black & white film.
This is how the camera adjusts the shutter speed and aperture to ensure the right amount of light reaches the film or CCD. Early cameras only had a manual mode (M) where the user had to select the aperture and shutter speed manually to ensure the correct exposure. Over the years cameras have become more sophisticated and now offer several automated modes including Program (P) - a fully automatic exposure mode that sets the aperture and shutter speed; Aperture priority mode (AP) where the user selects the aperture and the camera sets the necessary shutter speed; and shutter priority (SP, or Tv on some cameras) where the user selects the shutter speed and the camera sets the necessary aperture. Auto bracketing (AB) takes a pre-selected number of photographs, one at the suggested exposure and one to either side, so you can be sure of one accurate result. There are also several subject-based program modes that we haven't listed here that tailor the camera for particular subjects such as sports (action), landscapes, portraits, or flowers (close-ups). Some digital cameras have black & white and sepia modes. Buying advice A full auto program mode is ideal for point-and-shoot photography, but it's also useful to have some control over the exposure. The beauty with digital is that you can see whether the camera has got the shot right by previewing the image on the LCD. If not, you try again. If there is no manual control you can often preset the exposure using an auto-exposure lock or exposure compensation. The subject based program modes are often a waste of time and don't really bring much to the package. Special effects modes on digital cameras are also throw-away because all these can be created using the computer later.