Monday, 17 September 2012

Tungsten and Flourescent Lighting - Part 1

Part 1 - Tungsten Lighting

For the first part of this exercise take 3 images composed indoors under tungsten lighting at dusk when the light levels indoors and out are approximately even. Take 1 image with the white balance (WB) set to auto, another at  daylight WB and the third set to tungsten WB. Compare the results.

Comparing the indoor tungsten to the outdoor lighting shows that tungsten lighting produces a warm yellow/orange colouring to a scene. The outdoor lighting appears blue in comparison. All 3 images were taken using spot metering and aperture f/5.6. ISO640 was used to increase the shutter speed and allow the images to be taken handheld.

Image 1 - Tungsten WB
Tungsten WB
The first of these 3 images was taken with the camera WB set to tungsten. Interestingly this recorded the colour temp of 3000 kelvin. This is lower than I expected as I believe tungsten light to be generally regarded as between 3200 and 3400 kelvin. However the scene has recorded much as I remember. The warm yellow colouring indoors created by the artificial light contrasting with the cooler outdoor light. Further reading on the kelvin scale in relation to tungsten lighting indicates that the colour temp of a tungsten light source can be anywhere between 2500k and 3500k depending on the wattage of the light source.

Image 2 - Auto WB
Auto WB
The second image shows an auto WB setting in camera. This recorded a colour temp of 3300 kelvin. Again the auto setting in camera has done a good job and recorded the scene quite accurately. There is only a subtle difference between the two images and I would say either are acceptable.

Image 3 - Daylight WB
Daylight WB
The final image in the series was taken on daylight WB. This recorded a colour temp of 5200 kelvin. This shows a much stronger yellow colour cast resulting in an unnatural colouring of the scene. The added yellow has resulted in the outdoor light moving from a blue tone towards green. If you concentrate on the window frames in the image which are actually white you can see how well the tungsten WB and auto WB in camera has dealt with the light conditions when compared to the daylight WB setting.

The results of this exercise show that both the tungsten and auto WB are fairly close in appearance and in this case either would have been acceptable with the daylight WB being the most inaccurate and giving a yellow/orange colour cast.

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