Exercise 7: Tungsten and fluorescent lighting.

"Find a room lit fairly brightly by tungsten lamps, wait until just after sunset, when there is only a little daylight left.  With the curtains open, stand close to the window and look out for about a minute, until your eyes become adjusted.  Turn and look into the room light, what colour does it seem to be in the first instant that you see it?  After your eyes become adjusted to the room light, about a couple of minutes, turn back, now looking out of the window at daylight, what colour does it seem to be.  It is important to do this test when the daylight is weaker than the room light".

I did the above test and found that after looking out at the daylight, for a brief moment the room looked quite yellow.  The reverse happened when I then looked back outside the daylight was blue and cold looking.  The effect is similar to images taken in tungsten light with the white balance set to daylight and of course the opposite, with the white balance on tungsten taken outside in daylight.  Using the camera's light meter I measured the amount of light within the room.  I set the lens at it's maximum aperture of f2.8 and the camera to ISO 100, the average reading within the room was 1/20th sec.  As I was hand holding the camera and wanted to avoid blurred images, I adjusted the ISO to 1600 which enabled a shutter speed of 1/60th sec at an aperture of f5.6.

This is an example that no matter how good camera's are, they can be fooled.  The first image where the white balance was set to auto has been influenced by both light sources, the outdoor brickwork has a blue cast, the inside, lit by tungsten lights has a slight yellow tint.  The second picture has the correct colour outside but a pronounced yellow tint to the room.  Last taken with tungsten white balance, this image is very blue outdoors in daylight, however the colours inside the room look about right.

"For the second part of the project find two interiors lit by fluorescent lamps.  If possible make one of these an interior lit by small CFL lamps, take two or three photographs identically composed in each location.  The first image should be with the white balance set to auto, the second to fluorescent, compare the results and note the differences.  One thing should be obvious, the overall colour quality in all of them looks in some way unsatisfactory, fluorescent lamps do not emit a full colour spectrum".

The first pictures were taken at Jack & Irene's small holding where we buy our fruit and veg, I've taken photographs there before and knew that in Irene's shop and Jack's workshop they had fluorescent lighting, perfect for this exercise.  There are more than the required photographs, because I have included images from both the shop and workshop for comparison, also, there is a picture taken with daylight white balance.

As expected none of the images are exactly correct as far as colour is concerned.  The fluorescent lighting is responsible for this but also the fact that I had to use a high ISO of 12800 might have made a difference, it is certainly the cause of noise in the photographs.

The next three images were taken in my kitchen, where I believe we have CFL lamps fitted in the ceiling.

The photographs of the kitchen taken using the camera's white balance settings have various degrees of a yellowish colour cast to them.  The image taken with Auto WB was adjusted using the white balance correction in the raw converter of Photoshop. I used the eye dropper tool to sample the sink knowing this to be white.  I've included the finished photograph above, for comparison.