The Properties of Light

Light is created by a source and has five primary properties.

Light is created by a source and has five primary properties.

What you need to know about light

As photographers we use light all the time. Recording light is our way of capturing the world. Every single photograph is the result of a capture of some state of visible light. So just what is light?

Light is emitted by a ‘source’. Sources that create and emit light can be artificial or natural. The incandescent bulb in your room and the sun are both sources. ‘Visible light’ is the part of the ‘Electro-magnetic Spectrum” that we can see. The sensor on modern digital cameras focus on the same visible light as we do.

Every light source has five properties affecting the quality of its light.

  • Hard or Soft (or in between);
  • Intensity;
  • Direction of travel;
  • Colour;
  • Polarisation.

Each of these have special attributes that affect how we view or use light. Lets look at them in turn.

Hardness or softness of a light is related to its size and distance from the subject. A relatively small light which is distant creates hard light. A soft light source is relatively large and close. As light softens the shadows lose the hard edges and transition from light to dark widens.

Intensity is the amount of light emitted by a source. It’s measured in something called Lux External link - opens new tab/page. Photographers record light with an ‘exposure‘. The intensity of a light is similar to the brightness. In a bright light we can use a shorter exposure. Brightness is important because an intense light source may make the subject of our photograph very bright. Light intensity needs to be controlled in artificial lights. Too bright and we over-expose our shots. Too dark and the shot looks dark and dull. We can control intensity by using a less powerful source, turning it down or reducing its intensity by blocking it in some way using a whole range of light modifiers or reducers/diffusers.

The direction of travel of light is important because more direct light is harder. Direct light in the lens will tend to be brighter than reflected light too. When working with direct light you may need to consider using filters to prevent burning your sensor or at least blowing out your picture (losing detail in the bright spots). It is dangerous to your eyes to look at a direct light through the lens (avoid looking directly at any bright light). Since we tend to record reflected light we should consider the direction of travel of light from both the source(s) and the subject(s). The direction of travel determines our shadow/light relationship. It is this latter relationship that shapes the texture and contrasts of our scene. A shallow incidence of light creates longer shadows which is considered more atmospheric and better defines the subject. A full-on incidence of light will create few or no shadows making the subject look flat and lifeless.

Isaac Newton proved that white Light is composed of a range of colours – the visible light spectrum. Each colour can be separately produced by a variety of methods including filters, prisms, reflections, coloured translucent gels and atmospheric processes (dust or moisture in the air). The colours we see are the result of reflection. Plants are green because green light is reflected by the cells while other light is absorbed. Red paint reflects red light and absorbs the rest. The colour of light is important to photographers. It describes the scene we are photographing. Consequently we should be aware of the colour of the light reflecting from our subject(s) and the colour of the ambient light. Ignore ambient light and its ‘colour cast’ may affect the final picture. Reflected light is likely to create a colour cast – light picks up some colour off the surfaces it bounces off. Awareness of colour around us is one of the photographers primary considerations in composing a photograph.

Polarisation of light arises from the way light travels through a medium. Light is a wave External link - opens new tab/page. Its characteristics are quite technical. It is enough to know that when the waves line up the angle of the wave in the light creates its polarity. Polarising filters can filter out the lined up waves. Light scattered by our atmosphere polarises sunlight and creates the brightness and colour of a clear sky. Photographers can use a polarising filter to filter out the polarised light which darkens the sky, intensifying the blue colour. Polarised light is also created by other mediums. Glass and water both polarise light. Light reflected off water or glass can be filtered by using a polarising filter. The photographer with a polarising filter can see into the water or through the glass unhindered by reflection. Polarised light is not recorded as a component of the data in a digital photograph. So polarisation cannot be manipulated as a function of the recorded data in the picture. Therefore any ‘polarising’ software used in post processing is simulated polarisation. Reflections cannot be removed by this method.

The quality of a particular light is a result of all of these properties of light. Light is never ‘good’ or ‘bad’. It can only be a judgement call of the photographer to make the decision about the quality they see. Good quality light makes your shot what you want it to be. By understanding the different properties of light you can analyse some of the attributes that you want to use. Using the light appropriately can make or break a picture. So, become obsessive about studying light in all its moods.

By Damon Guy (author and Photokonnexion editor)

Damon Guy - Netkonnexion

Damon Guy (Netkonnexion)

Damon is a writer-photog and editor of this site. He has run some major websites, a computing department and a digital image library. He started out as a trained teacher and now runs training for digital photographers.
See also: Editors ‘Bio’.
See also: Profile on Google+.

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