Available Light - Tungsten and Fluorescent (4.4a)

Requirement

• 3 images - Tungsten Light (1 scene x 3 WB settings) 
• 4/6 images - Fluorescent Light (2/3 scenes x 3 WB settings)

Purpose

• To learn how to minimise, if not avoid, colour casts from artificial light sources

Technical learning

• 2 distinct types of artificial light: (a) available light and (b) photographic light (e.g. flash)
• 'Available' light is artificial light used to illuminate interiors, buildings, etc, which is not specifically designed for photography
• It is of 3 types: (a) tungsten, (b) fluorescent and (c) vapour discharge 
• Tungsten - used as domestic lighting, it looks orange or yellow to the eye and reddish to the camera. Most cameras have a setting to correct this type of colour cast
• Fluorescent - commonly used to light public areas. It appears white to the eye and an uneven mixture of colours to the camera.  Most cameras also have a setting to correct this type of cast 
• Vapour Discharge- used mostly for street lighting, building or stadium floodlights. These are of several types: (a) Sodium Vapour lamps look yellow to the eye and photograph yellow or yellow-green. Since this light source has no blue, it cannot be corrected by adjusting White Balance. (b) Mercury Vapour lights look bluish white and photograph blue-green, requiring a red filter to correct. (c) Multi-Vapour lights also look bluish white but actually photograph as white light.

Exercise instructions

Part 1 - Interiors lit by Tungsten Light

• Wait until immediately after sunset (i.e. when the light outside is less intense than inside the room lit by tungsten bulbs)
• Stand close to the window and look outside for a minute until your eyes become adjusted to the external light. Then turn back towards the room. (a) What colour does the interior light seem to be (i.e. before your eyes adjust)? Then, when your eyes are adjusted to the light in the room, look outside again. (b) What colour does the exterior light seem to be?
• Next, measure exposures around the room using your camera's meter, particulalrly close to a reading lamp as well as in the darkest part of the room. At ISo 100, what are the shutter speeds between the brightest and darkest areas of the room?
• Now compose an image which includes the brightest and darkest parts of the room and the external view, and shoot 3 times with the following White Balance settings: Auto, Daylight, Tungsten
• Compare results

Part 2 - Interiors lit by Fluorescent Light

• Find 2 different scenes lit by fluorescent light
• Take 2/3 image at each location with the White Balance set to (a) Auto, (b) Fluorescent and, if possible, (c) and alternative Flurorescent
• Compare results (note: colour quality in all should look in some way unsatisfactory)

Images and review

Part 1 -  Tungsten Light

Didn't do this exercise

Part 2 - Fluorescent Light

Shop Window

Auto WB = 4,950k
Over yellow

Fluorescent 1 = 3,100k
Over blue

Fluorescent 2 = 3,800k
Close to human perception of
the colour of the light as it was
when image was taken