Properties of light (11)

Requirement

None specifically

Purpose         

To consider some basic concepts of light important to landscape photography

Technical learning

The crucial element

• Light has the single greatest impact on a landscape image
• In considering light in the landscape, see it as a large outdoor set, with lights (the sun), reflectors (blue sky and clouds) and diffusers (clouds and, depending how reflective it is, the land, e.g. sand, snow vs grass fields)

Light and weather

• Weather controls light and also determines the appearance of the sky. (Being able to predict weather conditions is a key skill for the landscape photographer.)
•  Light changes constantly. The angle of the sun changes, so do the clouds and shadows and so on
•  The landscape photographer must work with and use changing light. Patience is a virtue. Sometimes the most important decision is when to shoot (and when not to avoid becoming snap happy and losing focus)

5 types of light in 2D image (see also separate page)

• Specular highlight - gives a mirror like reflection of the light source based on the positioning of the eye
• Diffused light - shows the true texture and colour of a subject
• Shaded side -  shows part of object sheltered from direct light
• Reflected light – light reflected from the surface of another object
• Shadow – absence of direct light surrounding object
• First 4 types of light give information in the 2D of an image about the colour, texture and shape of an object. 
• The fifth value (shadow) shows where an object lies in its surroundings as well as the shape and texture of these surroundings

Natural light in landscapes

• Important to make mental separation between the physical elements and light
• Natrual light has 4 variables: (a) sun’s position, (b) atmosphere, (c) weather and (d) surroundings    
• Sun’s position in sky – depends on the time of day, season and latitude 
• Atmosphere – softens light, especially when sun is low (i.e. light has to pass through more atmosphere), and scatters it (blue the most, hence the usual colour of a clear sky)
•  Weather -  filters and reflects light in numerous ways (clouds, haze, fog, mist, dust, rain, snow, pollution)
• Surroundings  - block light as well as reflect it

Colour of daylight (see Images below)

• Human eye, unlike digital sensor, adjusts for colour differences in light with a bias towards ‘white’ daylight (chromatic adaptation)
• Colour temperature, using the Kelvin scale,  describes the main colour differences of light, following what occurs when metal is heated
• It is used (a) to identify filters to adjust colour or tones and/or (b) to adjust the white balance of a digital camera, say, to remove the orange colour of tungsten light.

Images and Review

Experiment in using Camera Raw Colour Temperature adjustment

• Temperature control sets the image white balance to a custom colour temperature
• Decrease the temperature (i.e. increase blue, reduce yellow) to correct a photo taken with a lower yellow biased colour of light, such as candelight (1930k) or domestic tungsten (2500K)
• Conversely, increase temperature (i.e. increase yellow, reduce blue) to correct a photo taken with a higher bluer colour temperature of light, such as blue sky (10,000K),  shade under blue sky (7,500k), daylight deep shade (6500K) or overcast sky (6000K)

As shot in camera with digital
camera set to Auto White Balance
for a midday summer scene
with shadow in foreground and
sunlit middle and background

As adjusted in Camera Raw using
the highlight of metal rail in the foreground
to set the image's neutral grey. Reduces colour
temperature (increases yellow) by 650K

As adjusted in Camera Raw making
the maximum reduction in colour temperature.
Gives the image a yellow colour cast

As adjusted in Camera Raw making
the maximum increase in colour
temperature.
Gives the image a strong blue cast