Tuesday, 12 January 2016

Studio Lighting Guide

It is essential to get the lighting right in a studio used for painting as it can affect the ability to accurately judge colour relationships and match pigments.

Natural Light

The ideal situation is to have natural light with characteristics that are consistent throughout the day and for this reason painters prefer North light.  It is not recommended to have direct sunlight because it will be subject to constant change throughout the day, according to the height of the sun in the sky and the weather conditions.

Ideally an artist would want roof lights in the form of Velux windows on a North facing pitched roof.  Avoid low windows because they can cause reflected light which occurs when the light comes in, then bounces off the ceiling, and bounces down again.  Velux windows positioned at a 35 degree angle from the canvas provide directional light without glare, which can be an issue when painting on an easel with oils.  The easel should be positioned opposite the light source so that the light comes in from behind and above as in Francis Bacon's studio pictured below.

Francis Bacon studio lighting

Artificial Light

Artificial light is important so that the studio can be used in the winter months and at night when the natural light is poor.  When designing a new artificial lighting scheme for an art studio it is important to take the following points into consideration before choosing your light fittings because the choices you make will determine your future ability to judge colour relationships and mix pigments accurately.

1. Correlated Colour Temperature (CCT)

The colour temperature of a bulb ranges from reddish orange via yellow and then to white and blueish white and is measured in the Kelvin scale.  Colour temperatures over 5,000 K are cool with a bluish white light.  The ideal range for an art studio is 5000 to 5500 K which gives a white light that is neutral enough not to interfere with the colour of pigments.

The most common colour temperatures of light are as follows:
  • A regular household incandescent bulb: 2,500K to 3000K and gives a warm glow.
  • Office fluorescent light: 4,000 K to 5000 K and gives a cleaner, cooler light.
  • Noon Daylight: 5,500 K.
  • North Light (blue sky): 7,500 K to 10,000 K.
A light fitting with a bulb that is too warm might have the effect of tinting your paintings a reddish yellow, whereas too cool a light can give a blue tinge.  For a good balance of warmth and coolness find a bulb with a CCT of 5500 K, the equivalent of midday sun. If you prefer cooler light, akin to north light, look for bulbs rated 6500 K.

2. Colour Rendering Index

The Colour Rendering Index (or CRI pronounced 'cree') measures the ability of a light source to render a full spectrum of colours perceptible to the human eye.  The CRI rating indicates the bulb's ability to illuminate colour.  Natural daylight is full spectrum and has a CRI rating of 100.  The ideal range for an art studio is 90 to 100.  It is really important that your light source is able to render colour so that you can mix pigments accurately so try to get as close to 100 as possible.  The the highest CRI rating lighting manufacturers produce with a 5000K – 5500K is currently around 98.

3. Lumen's

Lumen's refers to the brightness or luminosity of the lighting as perceived by the human eye.  Lumen's measures the amount of light which is emitted from the light bulb so the higher the lumen's rating the brighter the light.

lumens to watts chart

  • 40-watt incandescent bulb = 450 lumen's
  • 29-watt Halogen = 450 lumen's
  • 9-watt LED = 450 lumen's
  • 9-watt Compact Fluorescent Lamp = 450 lumen's
Lux  refers to the level of brightness at a distance in meters from the light source.  The recommended lux level for detailed drawing work is 1500 – 2000 lux.

4. Wattage

Wattage is the measurement of the amount of electricity a light source uses.  The lower the wattage the more energy efficient and therefore cheaper the lighting will be to run.

To achieve the consistent artificial illumination of the entire studio space and having taken all of the above into consideration, full spectrum fluorescent tubes have recently been the next best thing to natural North light.  Fluorescent tubes are described by the diameter of the tube.  The popular T12s have now been discontinued and even the T8s and T5s are being phased out in favour of more energy efficient bulbs.

LEDs are the latest on the market and offer the most energy efficiency but the range of designs of the fittings is currently limited.  Also, they do not currently fit all of the criteria discussed above.  I have struggled to find an LED that has a CRI over 90.  

5000-5500 100
1 Gardner & Scardifield Ltd Algebra LED 4000 >90
2 Gardner & Scardifield Ltd Floodline LED 4000 >85
3 Osram Colour Proof T8 5000 90

I couldn't find a T5 to match the specification and I was disappointed with  values of the LEDs.  Having enquired with three suppliers I decided that the Osram Colour Proof T8, which has been specified for use by graphic designers, photographers etc, has the best output performance. The downside is that it isn't as energy efficient but for me the lighting quality is essential.

No comments:

Post a Comment