How Surfaces Change With Artificial Light
In a previous article we broached the topic of reflectance and how light is calculated and quantified when estimating the amount of illumination required in a space. We focussed on an often overlooked factor ‘Surfaces’ and the variety of ways they perform under certain lighting conditions.
We will now look in more detail at how a surface in a space is likely to respond to artificial light and the factors that we should be aware of as specifiers when selecting light sources and fixtures for our projects.
I am sure we have all taken a swatch of fabric or tile, outdoors of the showroom in order to gauge how our selection might appear without artificial interior lights. It seems that daylight becomes our control source when we want to be discerning. However this a mistake!
How Light Reflects
Firstly a quick reminder on lighting theory: Naturally, without light, we would not see anything. The colour of an object is the reflectance of light emanating from the surface of the object. Essentially, the nature of the light shining on that surface will be a factor determining what type of light is ultimately sent to your eye. Therefore, we need to be careful with the selection of that all-important element – light.
Paint Mix Analogy to Explain Reflected Light
As an example, let us imagine mixing up watercolour paint. If we use water that is clear and fresh, your colour mix would be untainted. Take the same mix, but this time use water that has already cleaned a blue brush, the blue in the water now influences the result. If we have a yellow tinted water, the result is different again.
This paint analogy can be helpful when thinking about direct lighting or specifically light that shines directly from the source onto the surface. It will alter the colour of the surface material. The fresh water to mix the paint would represent a neutral white light which we could classify as a 4000K colour temperature – a neutral white. The blue dyed water we will label as daylight 6500K and the yellow as a warm 2700K.
How to Control Reflected Light
The lower the colour temperature, the warmer the white light – the higher colour temperature, the bluer the white light becomes.
Under controlled conditions, this is how we should view the ‘mix’ of light, as it plays upon the surface and how our eye will see it. We should keep this in mind as we estimate how the chosen surface will look in situ.
Naturally, the real world is a more complicated combination of direct light, reflected light and shadows. So our directly lit surface is also influenced by light bouncing off other surfaces, where the light is tinted just like the coloured paint water and coming from different directions.
Controlling Reflected Light
OK – this is helpful to know but let’s get real, how many of us can really calculate what is actually going to happen?
Reflected Light Case Study in a Bathroom
Lets take a look at a real life case study. Thank you Gloria of Tailored Living for allowing us to use this. She had designed and chosen the finishes for a bathroom, we had supplied the lighting using trimless downlights with 3000K GU10 LED lamps and 3000K LED IP66 Flexi tape in a frosted aluminium low profile extrusion. Gloria sent us a follow-up query regarding the interaction between the tiles seen in natural daylight compared to under LED light.
Hi Andrew, could you have a look at these tiles in the bathroom currently being installed. When seen in daylight the tiles match (see pic A panel above) but now they are on the wall they look a different colour (see pic B panel above). Is this a function of the LED and is there anything that can be done to remedy this?
Gloria’s intention was to match a flat surfaced tile with a partner tile from the same range – that featured a relief pattern. Under her ‘habitual’ conditions of daylight testing they matched – but once installed they appeared differently.
Why Do Bathroom Tiles Look Different Once Installed?
The query was raised during the refurbishment with the lighting already installed. Side by side (picture) you can see the colour of the tile looks different with the flat tile appearing darker than the one with the 3D pattern.
At this juncture of the project, the bathroom was part tiled so the illumination was very ‘strong’ from the downlight, emphasising the form of the 3D tile; the tops of the form were highlighted creating shadows underneath. This made the reliefed tile appear brighter in comparison to the flat tile whose surface was vertical. You wouldn’t think it would make a major difference but it was this contrast that was the nub of the problem.
Solution: To bring the colours of the tiles closer we would need to reduce the contrast.
I assured Gloria that once the whole bathroom was tiled, the walls themselves would help the fix. A tiled wall is shinier than a matt unfinished plaster wall present during the install, boosting the reflectance performance. The light from the ceiling would go further and add an ingredient to the mix of direct light with the reflected light from the tiles – picking up some colour from the tile itself. It’s all very subtle but sufficient to be akin to putting a watercolour wash over all the walls balancing the variations with a uniform colour of light.
Once the all important mirror in a bathroom was installed, it operated as a fantastic reflector of light – back into the space and with the floor installed the light bounced back and upward more efficiently too.
Lighting Reflectance Reduces Contrast
After improved reflectance from the walls, the light would then be directed from more directions and effectively reducing the contrast of the lights and darks of the relief pattern. The walls themselves become effectively light sources so the pattern is lit more perpendicularly, further decreasing the shadow. This could also be achieved by adding wall lights that would throw light across the room rather than mostly downward from the bathroom downlighters.
The end result of the bathroom was stunning with the ‘natural’ contrast of the tiles reduced once the installation was complete. We all need to remain aware of the nuances of reflected light to inform our lighting design choices.
Remember – if things go wrong with the essential look of a scheme under your chosen lights – don’t panic all is not lost! Just call the team at Orange Lighting and we will be happy to advise on a solution to even the most thorny problem.