This exercise is all about colour variation. As the wording to the exercise suggests the human eye, or maybe more correctly the brain compensates for the changes in light source to a degree so the colour change as a result of staring at a dusk sky is adjusted for and nd the yellow tinge of the lighting is gradually reduced.
For the first part of the exercise I shot in spare room . This is lit by two tungsten lights, and bedside lamp, and is very neutral in colour.
First I took some shots of the differentially lit areas of the room using spot metering:-
Under the desk .4 sec at F2.8 (widest aperture) ISO100
- Ceiling 1/15 at f2.8 ISO 100
Light 1/250 at F2.8 ISO 100
- Bedside light 1/200 at F2.8 ISO 100
Obviously the variance in shutter speed may be less if using a different metering method but these four shots do, I think, illustrate the variance of light in the room.
The exercise asks you then to shoot an image covering both the lit interior and the exterior at dusk using three settings of white balance, auto. daylight and tungsten.
Bedroom window with white balance set on auto. 1/15 @F2,8 ISO 100
Bedroom window with white balance set on Daylight. 1/13 @F2,8 ISO 100
Bedroom window with white balance set on tungsten. 1/13 @F2,8 ISO 100
As can be seen the auto setting as noted elsewhere makes a pretty good stab at the colour balance of the interior and is not too far adrift from the equivalent tungsten image. Daylight creates what is an overly orange cast to the picture but probably represents the sky better by toning down the blueness of it.
For completeness’ sake I took three shots at another angle for comparison.
Landing window with white balance set on auto 1/15 at F28 ISO 100
Landing window with white balance set on daylight 1/15 at F28 ISO 100
Landing window with white balance set on tungsten 1/15 at F28 ISO 100
This time there is a bit more variation between the auto and tungsten shots, the latter representing the interior more accurately while the auto is taking on a very slight orange cast which is significantly increased in the daylight shot.
The next part of the exercise asks you to find and shoot two areas lit by fluorescent lighting and use three settings Auto, Fluorescent and alternative fluorescent. My camera has four settings for fluorescent:- warm white, cool white, day white and daylight. I have to say I have not, until this exercise , looked into the differences of these settings but thought it would be useful to do a full comparison of all of them.
The first location I used was the extension, which I thought made a good subject as it was possible to get a bit of the late day sky in the frame.
Extension shot with white balance on Auto. 1/6 sec at F2.8 ISO 100
Extension shot with white balance on daylight. 1/8 sec at F2.8 ISO 100
Extension shot with white balance on Fluorescent (warm white) 1/6 sec at F2.8 ISO 100
Extension shot with white balance on Fluorescent (cool white) 1/6 sec at F2.8 ISO 100
Extension shot with white balance on Fluorescent (day white) 1/6 sec at F2.8 ISO 100
Extension shot with white balance on Fluorescent (daylight) 1/6 sec at F2.8 ISO 100
Note how the auto setting corresponds closest to fluorescent day white setting, and both give a reasonably balanced image colour. On the other hand the daylight setting and its fluorescent equivalent give too much of an orange caste. The fluorescent warm white gives, as a contrast so to speak, a blue cast which is particularly noticeable both in the sky and the reflected windows. The fluorescent cool white setting reduces the blue cast but it is still noticeable. The patch of light coming through the doorway at the right hand side of the extension is from a tungsten bulb and it is interesting to note how that colour of that patch varies in the series.
Similarly, in the following series, the room beyond the door is lit by tungsten lights. I did consider closing the door but thought that the wall and the wood would be an further indicator of colour change due to the white balance setting.
Kitchen with white balance set at auto. 1/4 sec at F2.8 ISO 100
Kitchen with white balance set at daylight. 1/6 sec at F2.8 ISO 100
Kitchen with white balance set at fluorescent (warm white). 1/8 sec at F2.8 ISO 100
Kitchen with white balance set at fluorescent (cool white). 1/8 sec at F2.8 ISO 100
Kitchen with white balance set at fluorescent (day white). 1/8 sec at F2.8 ISO 100
Kitchen with white balance set at fluorescent (daylight). 1/8 sec at F2.8 ISO 100
Notice how this time it is fluorescent (warm white) that most closely resembles the auto setting although of the two I think auto is closest to my (perceived) reality. I am unsure as to why daylight, and to a lesser degree, fluorescent (warm white) have a green cast (more pronounced in the former) has such a green cast but clearly the temperature the camera has chosen accentuates, and unrealistically so, the green already in the image. As indicated in the course notes I don’t think any of the fluorescent settings are perfect but they do come near.
What has come out of this exercise is that the auto white balance function does a pretty reasonable job of getting the colour temperature right. It’s certainly given me reassurance that if I leave the camera set to auto white balance its unlikely (except in extreme situations) to be too far out.