Wednesday, 31 August 2011

Tungsten and Fluorescent Lighting

This exercise is now increasingly difficult to do because of the changing law and the lack of simple tungsten lights available. All the lights in our house are now the long lasting compact fluorescent light variety or halogen lights.  I performed a similar exercise looking at the lights (CFL) in the hall and out the door. When my eyes had adjusted to the outside light and I looked back inside the light was definitely orange. Conversely, when looking back outside, the evening light appeared bluish.
On measuring the light inside the living room, which appears reasonably bright to the eye, at ISO 100, and f/4.5, the shutter speed varied between 4 seconds in the brightest part of the room and 3 minutes in the dullest part, clearly not holdable by hand, and unlikely to give a sharp photo of a person. I am certainly aware that reading by the artificial light without an extra ‘reading lamp’ is getting increasingly difficult.

Interior and Exterior.

As previously noted we do not have any tungsten bulbs, so this exercise was carried out in the living room which is lit by a ceiling fitting of 5 small CFL bulbs.

Trial 1.

On investigation my camera does not have and automatic - fluorescent setting for white balance - so I did some experimentation.


This image was taken using the camera's AWB setting. Both the colour and exposure are reasonable. The internal light was from a overhead fitting of CFL bulbs that are diffused though  opaque glass light shades.


Here the white balance was set to incandescent, this is clearly not at all the right setting for these CFL bulbs and gives an overall blueish tinge both to the area of the pot lit by the internal lights and the outside area. Not a success.

Trial 2.

I then decided to experiment a little and see if I could get a better result in camera, without relying on post-processing. By now it was later and there was less light outside.


Again the camera's AWB setting has done a reasonable job. The curtains and the orchids have a fairly accurate colour and there is no overt colour tint to the outside, the window frame is a little bit warm in colour (it should be grey).


This was taken using the camera's daylight setting. It gives a warmer glow to the picture, more pleasant although rather less accurate  colours.


As previously, the incandescent setting does not work for the light generated by these bulbs.

Set whit balance

For this image I choose a white balance that I had previously set to a white card. This gave a very similar effect to the 'daylight' setting, possibly slightly more accurate, but still slightly warm.

This was an interesting experiment. Previously I would almost certainly relied on the AWB setting of the camera. I would not have used the incandescent setting, but also probably not used the daylight one. When taking pictures in our living room, which will usually be of family, the rather warmer 'daylight' setting is likely to give a more pleasing effect than the 'cooler' AWB setting.

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