Category Archives: 19a-Tungsten and fluorescent light

Tungsten and fluorescent lighting

Tungsten and fluorescent lighting

This exercise involves looking at the different colours of tungsten and fluorescent lighting so that I am able to identify which light is which.

Tungsten light

Tungsten lamps work by heating a filament until it glows. Ordinary household bulbs are tungsten lamps and are sometimes described as incandescent, which simply means glowing. They look orange or yellow to the eye but can photograph reddish. Digital cameras have a tungsten White Balance (WB) setting (called incandescent on my Nikon D5100) which can be used for shooting under tungsten lights which cools down the color temperature in photos

However, Präkel (2007, p77) notes that photographers should not seek to over-correct the yellow quality of tungsten light in domestic scenes, as viewers tend to associate yellow warmth with domestic interiors.

1. The first part of this exercise requires a room lit brightly by tungsten lamps and then waiting till just after sunset. You then look out of the window into the diminishing light for one minute before turning to look at the room light. Note what colour the room light appears. Look again out of the window and think what colour does the daylight appear?

I carried out this task and found that the tungsten lights in the room appeared very yellow, far more so that I recalled them to be. When I looked back outside the window the light looked to be blue. This helped illustrate the fact that our eyes have the ability to quickly adapt to light qualities.

2. The second part of the exercise asks that I measure the light levels in the tungsten lamp lit room. Will the camera at full aperture and the ISO set to 100, I took readings from various parts of the room. An area close to a lamp with a 40W tungsten bulb measure at a shutter speed of 1/10s. A plant in a corner read at 1.5s, as did a darker area leading to a hallway. This was too slow for handheld shooting and the resulting images were blurred. A bookshelf in a corner read at 1/4s and a vase of flowers near to the window measured at 1/8s.

This illustrates two things, the spread of tungsten light across the room was uneven and varied enormously depending on location and also that the quality of tungsten lighting is much weaker than that of daylight, around 2900K for a 40W household light bulb compared with approximately 5500K for daylight.

3. Part three asks that I compose a photograph in which an interior lit by tungsten lamps and the exterior at dusk are visible. When the light levels inside and out are roughly equal, take three photographs adjusting the WB as follows: Auto, daylight and tungsten. Compare the results.

I took these photograph to show both tungsten light and daylight in one image.

Auto WB

Auto WB

Daylight WB

Daylight WB

Tungsten WB

Tungsten WB

The Auto WB shot has given the image an orange tone, more to the objects inside than the buildings in the background outside. The colours do not reflect the original scene.

Daylight WB has given the interior a slight orange colour cast. However, the colours outside are a good match to those in the original scene.

Tungsten WB has captured the colour of the cardigan well and helped to pick up the navy blue of the stripes. The rest of the scene however, has a strong blue colour cast, which looks artificial.

It would seem that there is not one WB camera preset (on my camera) that can accurately balance a scene such as this, with light from differing sources and qualities. Perhaps this could be remedied to some degree by experimenting with a Custom WB setting?

Fluorescent light

Fluorescent light appears white to the eye but can photograph as greenish or yellowy. Präkel (2007, p78) explains that the reasons for this is that fluorescent light does not produce a continuous spectrum of colours, instead, it is a mixture of colour spikes. The quality of light also varies between manufacturers, the age of the light and the cost and application of the light.

Digital cameras usually have one or more WB setting to offset the cool shades of fluorescent by making them brighter and warmer. However, as the temperature of fluorescent lamps is so variable the fluorescent WB preset cannot be the ‘right’ balance all the time.

1. Find two different interiors lit by fluorescent lights. If possible, one should be lit by small CFL (compact fluorescent lights). Take two or three photographs in each location varying the WB from Auto to fluorescent. Compare the results.

The corridors in my apartment building are lit with, what I think are, CFLs therefore I took a photograph along its length with the different WB settings, Auto, which automatically adjusts the white balance and Cool-white fluorescent, the only fluorescent WB setting my camera has.* see note below

Auto WB

Auto WB

Fluorescent WB

Fluorescent WB

Auto WB has given the image a green colour cast while the fluorescent WB has compensated for the perceived coolness of fluorescent by adding‘warmth’ to the image. However, it has over-compensated and the results are very orange.

This basement car park is lit with fluorescent strip lighting.

_DSC1545

Auto WB

_DSC1547

Fluorescent strip lighting

The Auto WB image seems to contain a lot of blue with the green of the parking bays appearing very pale. The white car closest to the camera also appears bluish, as does the ceiling. The Fluorescent WB seems to have done a better jog at balancing the colours but it still not accurate, as there seems to be a slight pink colour cast to the ceiling.

This has shown me how varied fluorescent lights can be and because of this it is difficult to predict how they may light a scene.

Conclusion

Before this exercise I have tried to take photographs indoors under fluorescent lighting, with varying degrees of success in balancing colours. Now I understand a little more about how these lights differ from tungsten lights, I can appreciate why this would have been the case. Of course, unwelcome colour casts can usually be removed when editing however I think it is of interest to think of what feeling uncorrected light can evoke in an image, such as in Nightmare by Karl Fakhreddine, shown in Präkel (2007, p79).

* Since carrying out this exercise I have discovered that my camera (Nikon D5100) does actually have more than one preset for fluorescent WB. When exploring the shooting menu I found that there were seven fluorescent presets listed as follows-

Sodium-vapor lamps, Warm-white fluorescent, white fluorescent, Cool-white fluorescent, Day white fluorescent, Daylight fluorescent, High temp. mercury-vapor. 

The problem I now have is now trying to recognise these types of lights accurately. However, it is nice to know the meantime that if I take a photograph with fluorescent WB and it doesn’t look ‘right’, that I have other options to experiment with. 24/09/13

Präkel, D. (2007) Lighting. Lausanne, AVA

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