Photography 1: TAOP, Ex Tungsten & Fluorescent Lighting

Project: Available light.
Exercise: Tungsten & fluorescent lighting.

Part 1.
For the first part of this exercise I found a room that was fairly brightly lit by tungsten lamps.  I turned off any fluorescent lamps.  Just after sunset, when there was only a little daylight left that was weaker than the room lights, I stood close to the window and looked out for about a minute, until my eyes became adjusted.  I then turned around and looked at the room light.  The room light seemed yellow.  After my eyes adjusted for a couple of minutes, it seemed less coloured.  I then quickly looked out of the window again.  The daylight outside seemed blue.

I next measured the light level at various points in the room with my camera's meter.  I took several readings including close to a reading lamp, and in the darkest corner.  I set the aperture to the largest available, F4.5 and recorded the shutter speed:

1/10s; 1/15s; 1/20s; 1/8s (darkest part of room); 1/10s; 1/10s; 1/30s (near reading lamp).

None of these readings would be good enough for hand-held shooting.

I next composed a photo in which both the interior lit by tungsten lamps and the exterior at dusk were both visible.  I waited until the light levels inside and outside were approximately equal, and took 3 photos, as follows: with the white balance set to Auto, with the white balance set to daylight and with the white balance set to tungsten.  The three photos are shown below:

5569.jpg; F11; 1.5s; Auto WB

5570.jpg; F11; 1.5s; Daylight WB

5571.jpg; F11; 1.5s; Tungsten WB

With the white balance set to Auto, the camera has made a reasonable compromise with the colour balance with neither the interior or exterior completely correct.  With the WB set to Daylight, the colour of the daylight is good but the interior light is too yellow.  With the WB set to Tungsten, the interior light is good but the daylight is too blue.

Part 2.

For part 2, I found two different interiors and lit them by compact fluorescent lamps.  I took four photos of each location each identically composed.  The first image was taken with the WB set to Auto, the second set to Daylight Fluorescent, the third set to Neutral Fluorescent and the fourth set to White Fluorescent.  The photographs produced are shown below:

5572.jpg; F11; 1/2s; Auto WB

5573.jpg; F11; 1/2s; Daylight Fluorescent WB

5574.jpg; F11; 1/2s; Neutral Fluorescent WB

5575.jpg; F11; 1/2s; White Fluorescent WB

5576.jpg; F11; 1/3s; Auto WB

5577.jpg; F11; 1/30s; Daylight Fluorescent WB

5578.jpg; F11; 1/30s; Neutral Fluorescent WB

5579.jpg; F11; 1/30s; White Fluorescent WB

In each location, the White Fluorescent WB setting gave the best colour rendition.  This uses a colour temperature of 4200K, the closest to that of the CFLs used  which are calibrated to 2700K, (the colour temperature of a tungsten incandescent lamp).

What have I learned from this exercise?

Tungsten lighting is much weaker than daylight and in most rooms it is very uneven.

Many commercially available fluorescent tubes include a continuous spectrum as well as the bands of light produced by the fluorescent coating to give a more pleasant light.  This means that they can be given an equivalent colour temperature although they can still produce a green colour cast without adjustment to the white balance on digital cameras.