Saturday, March 30, 2013

Exercise 32: Tungsten & Fluorescent Lighting

With this exercise we examine three light sources:  natural daylight at sunset/dusk, tungsten lighting (that provided by typical light bulbs), and fluorescent.

Before shooting, we are asked to gaze out a window at sunset in a room lit with tungsten light.  After one minute, we look back into the room, then again back out the window to note the difference in lighting.  What I noted is the outside light was blue, inside orange.  The eyes quickly adjust to these changes as you move back and forth between light sources.

We were then to shoot a series of photos combining different types of light sources. The first set was shot about an hour before sunset and shows tungsten to have an orange cast, fluorescent blue-green.  





The second set was made at dusk, under tungsten, with different metering and different WB options. The first is a set with spot metering on the wall between the lamp and statue.  




 The second is identical but with matrix metering.




Under Tungsten WB we get a heavy blue light outside, a pale white inside.  With Auto WB a little less blue, a little more yellow, and with Daylight almost no blue and a heavy orange.  

Finally, two images under compact fluorescent were made after dark.  


With Auto WB we get a slightly green cast, but with fluorescent far too much orange. Ideally, the color should be somewhere in between.  

Implications?  

Practice more with light and WB settings and for the time being when opportunity permits take multiple shots under different WB settings.

As might be noted, the highlights around the lamp tend to be blown out in many images, particularly those using Auto or Daylight WB.  What I have done below is modify one image to achieve a better balance in the blue-orange spectrum of cast.  I did this by increasing temperature and exposure while decreasing highlights. The original is at left, the edited version right.  



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