Light: Project – Available Light; Exercise 34 – tungsten and fluorescent lighting

This exercise in the OCA’s Art of Photography  module on light deals with the challenges posed by tungsten and fluorescent lighting. We know from colour temperature theory (see Light – Science, Magic a core text for this programme and reviewed here) that equal amounts of red, green and blue light will give ‘colourless light – that which we see in a cloudless day in the open.  The colour temperature of colourless light 5500 degrees Kelvin. We also know from the same theory that light that derives from different artificial sources has  different temperatures and will, therefore not appear colourless, particularly to the camera sensor – which will not adjust in attempt to ‘normalise’ the colour in the same way our eyes/brain will.  In practise, where the light being used to illuminate a scene is not ‘colourless’ daylight there is a good chance that the image captured will have unusual casts unless there is a correction made in the camera (if possible) by adjusting the white balance or unless the light itself is ‘daylight’ balanced.

In this exercise two sources of artificial light are considered in two parts.

Part 1

In this first part tungsten lighting is considered, specifically its appearance at dusk when compared to daylight – as in the images below.  The first and most immediate affect is that if the two sources of light (outside daylight and tungsten lamp) are compared without sufficient time for the brain to adjust then the tungsten light is both less bright and more yellow in appearance. In the three images below the same scene is captured with white balance set at Auto, Daylight and Tungsten.  The effect of adjusting the white is clearly seen below.  in the first and second images the camera adjusts predominantly for the daylight and the colour of the scene outside is reasonably faithfully replicated.  in the third image, the tungsten setting applied adjusts the tungsten lighting more closely to colourless light but in so doing turns the light outside blue.

Auto

Daylight

Tungsten

Part 2

In the second part of the exercise the effect of lighting an interior with fluorescent lighting is considered.  In the first two images standard industrial fluorescent tubes light the interior of a garage.  The distinction between Auto and Fluorescent settings is not immediately obvious although there is a hint of a slightly bluer cast on the Fluorescent setting. It should be notes that the temperetaure of tubular fluorescent lights is quite close (5000) to daylight (5500) therefore any cast will not be immediately obvious.

Auto

Fluorescent

In the second pair of images an interior is lit with compact fluorescent lights (CFL).  CFL lioghts have a colour temperature of 3000 degrees k (quite different fro daylight) unless they are specifically daylight specified.  It is very noticeable in the two images below that the colour cast is very obvious.  The fluorescent setting does not deal with the warmer yellow while the auto converts to a ‘colourless’ daylight setting.

Fluorescent

Auto

Colour casts originating from the nature of the light source may or may not be acceptable depending on the artistic decision of the photographer.  For example, the fluorescent setting in the image lit by the CFKL gives a warm glow that is pleasant on the eye.  In contrast images such as this of a garage workspace might wish to show a slightly colder light to emphasise efficiency, etc.

Light: Project – Available Light; Exercise 35 – Outdoors at night

This exercise in the OCA’s Art of Photography Light Module deals with the subject of using available light outdoors at night.  The images were all made in or around my home town (Sligo) in north west Ireland.  in scouting for the locations a number of things became obvious.  First there were few floodlit public buildings.  Second, the town has few shopping centres.  Third, a great variety of light sources and colours are used in the town to light shops, shopfronts, and streets.  This generated a variety of challenges to the way in which the light was managed.  About 100 images were made of which 5 have been used in the sequence of images below.  Managing colour balance occupied my attention for most of this exercise and a systematic approach was used to making the first three sequences of images (floodlit building, lit store front and a large interior) as follows.

1. A set of images was made using the Auto white balance setting.
2. A set of images was made using the appropriate preset white balance setting (e.g. tungsten, fluorescent, etc).
3. A third set of images was made after the colour temperature function on the camera’s white balance menu (Nikon D7000) was manually adjusted in live view to as closely as possible match the scene.

In each case below the images that most faithfully resemble the colour of the scene are presented. The images were generally exposed to avoid large areas of blown highlights although in small areas of the images this was unavoidable if detail in the darker areas was to be captured. In all cases, the image that most closely resembled what was present was that in which the colour temperature was adjusted manually using the camera’s live view facility to check.  The images in which the Auto function was used tended to be normalized towards a ‘daylight’ setting.  This tendency was particularly marked in the case of the floodlit exterior and this image is shown at the end of the sequence.  The difference between the first and third images is obvious.  Despite the fact that the Auto Setting appears most correct it was the manual setting of white balance that was correct.

During the course of the exercise it did occur to me that it would be easier simply to shoot in RAW (as I do for all my underwater photography) and then adjust later.  However, if I did this without manually checking on live view  I would not know what the ‘correct’ colouration was. The belts and braces approach might be to shoot in both RAW and JPEG with the JPG image having been manually adjusted for white balance.  This would allow correctly a coloured image to be used in any RAW post capture processing.

Floodlit, Colour Temperature Adjusted Manually

Interior, Colour Temperature Adjusted Manually

Shopfront, Colour Temperature Adjusted Manually

Floodlit, Auto

The final image in the sequence above is the floodlit building shot on Auto white balance and it is clear how the setting has attempted to normalise the colour to a daylight setting. However, the image that is first in the sequence above shows the correct colouration.  The final image was set up to catch the streaks.