Colour Vision Experiments in the Grant Museum of Zoology
By Dean W Veall, on 26 January 2017
Lighting in museums is a curious thing. It can make or break an exhibition. It can make a dismal space beautiful, or vice versa. At the same time, subtle changes in lighting can have a meaningful effect on the amount of time that we’re able to display objects before they deteriorate past the point of no return. An example of one such subtle change might be the colour of the light. A barely noticeable change in colour could have a drastic effect on the damaging power of the light depending on the technology being used.
One unknown factor, however, is what exactly the visual impact of such a change might be. We’re still not entirely sure how the human visual system is able to adapt to changes in the colour of lighting, and that’s where I come in. During the course of my PhD I want to improve our knowledge of this process, and then work out what we’re able to do with museum lighting as a result of this knowledge.
This was the motivation behind an experiment I recently conducted at the Grant Museum of Zoology. Before we can start thinking about the mechanisms in play that allow humans to adapt to different colours of ambient light (we call this process chromatic adaptation), we need a reliable measurement tool for measuring how any one person is adapted at a particular time. A person’s state of adaptation is thought to primarily reflect the colour of the ambient lighting that they’ve most recently been exposed to.
Equipment for measuring this in controlled lab environments exists, but I was keen to design a tool that could be used in real environments that could be flexibly deployed wherever and whenever. Enter: the tablet based spatial achromatic point setting apparatus, or SAPS for short. SAPS consists of a tablet which displays a perceptually uniform colour-field (perceptually uniform: a distance in any direction equals the same level of colour difference)*, where a participant can be instructed to select the grey-est or least colourful point on the screen. This is repeated a small number of times and an average grey is calculated.
After each run, the participants got to see what colours they’d selected. While there’s no right answer, it was exciting to be able to see each individual’s different bias, and different levels of spread in the points selected.
We need to do future work to test whether SAPS is a viable tool for exploring chromatic adaptation in museum spaces, but this was a very valuable exploratory experiment, and the results were presented at AIC2016 conference (Association Internationale de la Couleur) in September.
* For the nerds in the room: it was a CIELAB chromaticity space, computed to account for display linearization.
Danny Garside is a PhD candidate based in the Department of Civil, Environmental and Geomatic Engineering at UCL, working on the subjects of museum lighting and human colour vision.