I’m up late tonight because I have a Zoom meeting for ISO Photography Standards, beginning at 11pm. I’m on a special ad-hoc committee to consider the issue of skin tone colours on photographic test charts. We specify various International Standard printed test charts that people can use to test camera colour reproduction. And of course skin tones are of crucial importance because of how sensitive we are to when they don’t look quite right, so many of the charts include patches of colours meant to represent skin tones. But the issue is that many of these were designed decades ago, and the representation is mostly based on European, light skin tones, with few or no darker tones.
So we’ve assembled a group of experts from around the world to consider how we specify these going forward, in a more inclusive way. We need to think about and discuss what range of colours to specify, how they should be reproduced and displayed, and how their reproduction should be quantified and measured. It’s complicated by the fact that our visual system is very finely attuned to skin tones, not just as flat colours that might be printed on a chart, but also by spectral reflectance, lighting and metamerism effects, subsurface scattering, angular effects, and salience effects caused by our brain’s innate ability to recognise the difference between an actual person and a patch of colour.
Some of the group members have been discussing in email the potential need to specify test charts with fully three-dimensional models of human faces with synthetic skin that includes translucent layers, which is a far cry from the traditional methods of testing camera colour reproduction with a printed flat chart with square patches of solid colour. So… I expect this Zoom meeting is going to be concentrating on what exactly the scope of our problem is, and how complicated we should go in addressing the fundamental problem of expanding the range of skin tones in our standards.
In other happenings, I basically spent all day today writing my lesson plans for this week’s new Outschool ethics classes, on the topics of Candy for the younger kids, and Fossil Fuels for the older ones. I also made quiche for dinner, using cauliflower leaves as the vegetable in the filling, which turned out pretty good. I’m pretty stoked to discover that the leaves on cauliflowers are not only edible, but yummy.
New content today:
Those test charts are interesting! Are the standards public or would I need to pay for them?
A long time ago I worked in a project making a mobile phone camera application. We experimented with some face-recognition libraries and ran into just that kind of problems. They worked fine with light skin tones, but anything more dark started to fail quickly.
I think we didn’t use them in the end. Still made a good product, though.
The standards are available for purchase from ISO, so public but not in the sense of available free of charge. But you can see a sample image of what some of these old test charts look like here: http://www.3nhcolor.com/product/205-323.html
You can see the colour patches, with a couple of “skin tones” in the lower left. This chart is more designed to measure camera resolution though, so doesn’t concentrate on colours so much. There are other charts with more colour patches on them.