• Fiona McNeill

The unbearable lightness of makeup

I have spent parts of this week reading a textbook on ‘Measuring Colour’. At one point, my husband looked at me and said ‘You look like you broke your brain.’

I did rather feel that way! Colour is a very tricky thing. It depends on the physics of reflected light. It depends on the way our eyes detect light. It depends on the way our brains process the information.

We perceive a colour partly because of the wavelengths of the reflected light we see. The colour changes as the light intensity changes. Other factors can also come into play. For example, the colour you perceive can depend on the colour it is next to.

Over the years, people have found that when describing or matching a colour, a very specific and accurate system is needed. There are several different systems used to identify colours. If you have ever painted your walls, you will have probably come across the Pantone colour system. Pantone have systematically numbered an enormous range of colours. You may also have heard of the RBG (red-blue-green) colour model. This was the model developed for colour television. TVs used mixtures of red, blue and green light to create the colours seen on a screen.

To measure the colour of make-up, I have been using the L* a* b* colour system. The L* a* b* system allows you to plot colours on a red-green and blue-yellow axis simultaneously. The green to red axis is the ‘a*’ part of the L* a* b* name. The blue to yellow axis is the ‘b*’ part of the name.

To be honest, I started with this system because it was built-in to the spectrometer package. However, now I really like it, because it allows me to look at colour shifts from green to red and from blue to yellow very easily. If you read last week’s blog, you can see the shifts to the red and the shifts in yellow that show up often when looking at lead make-up.

However, there is also the ‘L*’ part of the colour system name. This stands for ‘lightness’. It is best explained by showing you the effect of the lightness value L* on colour. In the picture, I have shown what happens to three colours as you decrease or increase the measured lightness value L*. I chose blue, red and white. Each step going up or down in colour is an equal step in L* value. L* is larger at the top.

Last week, I showed you the makeup I measured just before Christmas. It shifted the colour of pigskin to less yellow and more red. It also lifted the ‘lightness’ of the pigskin the equivalent of one L* step size. In makeup terms this means the pigskin moved to a lighter shade. We’d also probably say it looked ‘brighter’.

The lead make-ups we have tested so far would have lightened the complexion. The skin would have been a light colour, with the lightness varying with the thickness of the makeup. It would have been a slightly pinky yellow tint, not pure white.

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