Developing a good eye for tone is essential to skilful use of contrast. To develop your tonal perceptiveness and your understanding of how lighting creates tones, pay attention to the different visual effects created by bright sunlight, subdued sunlight of a rainy day, thick cloud cover and moonlight. Make quick black and white tonal sketches in a notebook to see how many tones you can see in each case, and how clearly you see them. Take particular notice of how different light sources effect   shapes by flattening them or making them more fully rounded. If you have no confidence in your drawing or observational skills (which require some practice), create a tonal strip on a piece of paper (like that on pg 17 of this subject guide, and use the strip to identify the different tones observable under different lighting.

Contrast can be divided into three areas:

• Subject Contrast
• Lighting Contrast
• Brightness Range

Subject Contrast
Different types of surfaces will reflect different amounts of light. Light colours reflect more light than dark colours. Shiny surfaces can reflect more than dull surfaces. When there is a greater difference in the amount of light reflected, there is a greater subject contrast. This is also called the ‘reflectance range’.

Lighting Contrast
This is the difference between highlights and shadows. If harsh, directed light (eg. a strong narrow beam) hits a subject; the overall contrast increases. Shadows do not reflect much more than they did without the extra light, but well lit areas reflect a great deal more … hence lighting contrast increases. The overall contrast in an image is a result of the combined affects of ‘reflectance range’ together with ‘lighting contrast’. This overall contrast is sometimes called the “luminance range”, which is determined by considering the following combined factors:

• luminance of the darkest and lightest objects
• luminance of selected middle-range object  (midway between darkest and lightest)
• overall effect
• incidental light.

If directional light or key light refers to the dominant light source, and fill light refers to any light that illuminates shadows, lighting contrast is the difference between the level of directional light and fill light. This difference can be measured in “stops” and recorded as the “lighting ratio”.

Brightness Range
Subject Brightness = Reflectance range X lighting ratio. Example: If a subject with a reflectance range of 32:1 (ie. a high subject contrast), is placed in strong directional light with a lighting ratio of 4:1, the overall contrast or subject brightness range (SBR) can be recorded as 128:1

EXPOSURE COMPENSATION
When the camera lens is pointed towards the light contrast will greatly increase. To help create the desired lighting, the photographer must identify the darkest part of the subject where detail is required and the lightest part of the subject where detail is required, and determine how to achieve that detail. Changing the exposure allows the photographer to compensate for insufficient contrast in either case. Increasing exposure will show more detail in shadows or dark coloured subjects. Decreasing exposure will show more detail in bright tones or lightly coloured areas.

Another way to compensate for excessive contrast is to have light-toned surrounding behind the camera reflect light back into the frame. This diffused light will reduce darkness and reveal more detail in the subject while preserving the effect of backlight. White paper or other reflectors and fill flash can be used to bring light into the frame.

Ways of Assessing Compensation
While experience photographers can determine exposures based on experience, most amateur photographers rely on exposure tables provided with the film, or a calculator on the camera. Where artificial light is used, most exposure calculations make allowance for the type and power of lamps, reflector efficiency, distance and direction of lamps. However, the calculations are still not very reliable, since so many factors can be at work, and the photographer might use ‘bracketing’ or other methods to ensure correct exposure. While learning, it is useful to keep a record of the exposures used for different pictures; experience will gradually make it easier for correct exposure to be determined.                  

Bracketing: This procedure involves making three exposures, one at the most likely value or meter-indicated exposure, and one on either side of that value (an over exposure and an under exposure). 

Grey Card: This is a contrast and exposure reference that reflects only 18% of the light that strikes it, and is used to help determine necessary exposure and shutter speed.

Polaroid: If using polaroid film with the same ISO and a similar contrast range to the film in your main camera, you can take comparable photos and see immediate results to get an indication of how lighting conditions might show up in a final print from the main camera.

Caucasian Skin: A light reading taken on normal Caucasian skin in the main light source is approximately one stop lighter than a mid tone of 18% reflectance.

Re-framing: This involves taking a reading quickly from a scene of average reflectance close to the intended subject.

Compensating For Lens Flare
Lens flare is re-reflected light from the lens, or light spill. It can cause tones to bleed or merge, especially in shadows, and may cause flare rings or images on the film that create an unclear final image. Lens flare can be reduced by using an appropriate lens hood, by multi-coating the lens, and by keeping the lens free of fingerprints and dust.