This week we learned about a concept that our readings call “color constancy.” I find this absolutely fascinating, because it changes the way we define color completely. Normally, one might claim that an object’s color can be measured by the wavelengths of light that it reflects back to our eyes. However, we saw very clearly from the optical illusions that Prof. Conway showed us in class that the way we label colors depends on more than the wavelength of light being physically reflected. It also depends on the colors surrounding the point we are trying to define; specifically, it depends heavily on the color of the illuminant.
As discussed, our brain recognizes that the light illuminating a scene has a certain color to it, and uses this knowledge to figure out what the scene would look like under white light. That way we can recognize objects under any kind of lighting; for instance, we know a red apple is red regardless of whether it’s physically reflecting the wavelengths available from white light, blue light, or any other color of illuminant.
I found it interesting that this subconscious pattern in our brain is very similar to how many scientific instruments are designed. Essentially, our brains are subtracting the background so that we can see only the significant data. This is how zeroing a scale works: if there is nothing sitting on the scale and you zero it, then add 1 g, the scale tells you there is 1 g present. If you put 5 g on the scale, then zero it, then add 1 g, the scale will still tell you there is only 1 g present. Zeroing the scale to take into account what was already there is just like our brain “zeroing” the color of the illuminant to take into account that there was already a color present before the object of interest came into the picture.
Another example is GC-MS data, which stands for Gas Chromatography and Mass Spectrometry. The GC part of the equipment separates a solution into the individual parts that were dissolved in it, much like the syringe in our kool-aid experiment from our first lesson on color. The MS equipment reads the masses of the substances coming out of the GC equipment. When looking at the MS data for the particular component you’re interested in, one has to subtract the background MS readings first. This is because the solution your stuff of interest was dissolved in also has a certain set of masses associated with it. If you get the MS reading without subtracting the background from the solution, you’re not actually reading data on your stuff of interest. You’re reading data on the stuff and the environment it’s currently in, much like without our brain’s calculations we would see the color of an object as altered by a colored illuminant. This information is useless, because you can’t tell if the readings are actually caused by your stuff of interest or not. If you subtract the background MS data, then you now have useful, relevant information (data for the stuff itself), just like how our brain’s calculations give us useful information (what the object’s color is regardless of illuminant).
I would assume these instruments were designed independently of findings on how our brain interprets color, so it is interesting that this incredibly useful system for analyzing information came to exist in different scenarios and in different ways. Apparently the need to dismiss background information in order to obtain relevant information is indeed that basic and universal.