Wednesday, 5 October 2011

Part 4 Light–Project: Available Light

Exercise: Tungsten and Fluorescent Lighting (Digital Camera)
Objective: By using different types of lighting coupled with camera white balance settings, I have aimed to demonstrate the variation in the colour of different types of light and how the camera settings can be used to compensate for them.
I completed the comparison test at the start of this exercise and noted that the room appeared yellow in the first observation  as did the outside in the second observation. I’m not sure if this is what was expected but there was a definite yellow cast outside from residual light of  the sunset on a clear evening. While I am prepared to accept that the eye could see what the brain expects, I’m not sure how objective this test can be.
I set my camera’s meter to ISO100 and the range of shutter speeds at full aperture (f3.5) was from 1/5 to 1/10 second. Not fast enough to hand hold.
I had to change the lamps to tungsten for this exercise and produced these three images using these camera settings:1/1.6s f5.6 18mm ISO100 tripod mounted
8139: White Balance: Auto
8140: White Balance: Daylight
8141: White Balance: Incandescent (Tungsten)
Including the lamps in the image has introduced burnt out highlights in all of them. The Auto setting has produced an almost identical image to the incandescent image with the exterior showing very blue. The daylight setting is very orange but the outside scene appears to  be normal daylight with just a hint of the late evening orange mentioned earlier.
For the second part of the exercise, I put the energy saving CFL lamps back into their holders. My camera has 5 different fluorescent white balance settings which include: white fluorescent, warm white fluorescent, cool white fluorescent, day white fluorescent and daylight fluorescent. I have shown images for Auto white balance, the fluorescent setting which shows the most accurate colour balance and an edited version in an attempt to correct it.
8190: 4s f11 18mm ISO100 (tripod mounted) WB: Auto

8192: 4s f11 18mm ISO100 (tripod mounted) WB: White Fluorescent unedited

8192: WB: White Fluorescent edited
My editing application (Capture NX2) has the ability to edit camera settings in RAW post production. There was not a satisfactory image so I have applied changes to 8192 as follows: Standard Fluorescent, warm white 3000K and a tint adjustment (magenta/green) of –2. You can see that the Auto setting is distinctly yellow.

My second scene is lit by a single white long fluorescent tube.
8196: 1s f11 18mm ISO100 WB: Auto

8199: WB: Cool White Fluorescent (unedited)

8199: WB: Cool White Fluorescent (edited)
I have edited the settings for this image as follows: Standard Fluorescent 3970K with a Tint setting of –1.

As indicated in the notes, the colour casts generated by fluorescent lights are wide and variable, although the range of camera settings available in increasing, fine adjustment with editing software becomes necessary to achieve a realistic white balance.

Conclusion: I have been aware of the colour temperature of light and used correction filters with film for many years. From this exercise with a digital camera, I now have a better understanding which settings to use and the fine fine tuning now available make corrections instantly or even retrospectively.

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