Sunday, 16 January 2011

Exercise: Tungsten & Fluorescent Lighting

In this exercise we are first asked just look out of  a window in a room lit with tungsten lighting after sunset for a minute then to turn and look inside the room. When I did this the room was immediately a very yellow shade. After my eyes had stabilised looking outside gave a bluer impression.

We were then asked to meter the room at various points, it was quite obvious that the room varied considerabley in available light by several stops, from the brightest parts around the lights to the corners of the room in the shadows; this is consistent with indoor tungsten lighting. In fact at f2.8 I would could only manage a shutter speed at 1/6 second at 100 ISO and the images in this exercise had to be taken at 1600 ISO as I did not have a tripod handy.

The next part of this exercise was to take three images through a window showing both the inside and outside. The three images were to vary by auto, daylight and tungsten white balance settings, all shown in that order below:

Firstly it can be seen that the daylight and auto white balance settings have given similar results, probably as the camera was focussed outside of the room. Here the white balance of the room is too yellow and incorrect, whereas the outside is perfect, similar to that of the first part of this exercise.

In the image where the white balance was set to Tungsten, the white balance of the room has been corrected but at a cost of the outside becoming too blue. 

The final part of this exercise is to take images inside a room lit with fluorescent bulbs, varying the images with  Auto and Fluorescent White Balance Settings. I only had access to a room with small CFL lamps and took the following images.

If I have to be honest there is very little difference in these two images, looking at them on the monitor the Fluorescent image has more colour and a little richer, but not much to speak of. I can only assume that the AWB setting on my camera has worked well. As stated earlier in this exercise I did not have opportunity for repeating the final part in a room with long fluorescent bulbs, but I do have a RAW image taken in a squash court full of fluorescent lighting and I am able to convert the RAW image with the required two white balance settings.

Here there is a difference in the colour of the walls, sadly though I think that the AUTO setting has actually taken a better image than the lower and bluer Fluorescent setting. In the first image the walls of this particular squash court are yellow, I am sure that this would have influenced the processing of the image too.

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