When I was photographing eyes a few weeks ago I came across a fascinating phenomenon:
The human iris and especially blue irises produce rainbow coloured gradients under cross polarization.
I used the cross polarization technique to cancel out harsh reflections of the speedlight that I used to illuminate the eye, which I was photographing, when I discovered rainbow gradients in the blue eye of my sister.
I had previousely noticed some rainbow coloured highlights in my own (brown) eyes, but not really quite enough to leave stumped and fascinated as when I looked at the image above on the back of my viewfinder.
After a bit more research and some testing with two sets of brown and two sets of blue eyes I was certain, that this effect related to the colour of blue eyes. Brown eyes have an additional layer of the pigment Melanin which sits on top of the iris. The darker the colour of the iris, the more of the pigment is present. This additional layer is the reason why such gradients won’t show up in brown eyes.
But why do blue eyes produce such gradients? Good question, next question please…
Even though I have a basic idea as of what the reason of this phenomenon might be, I am admittedly not quite certain of the physical process that causes these colours to show, so if you can explain the science please share you’re knowledge and I’ll add it to this post.
What I can share however is the process and the set-up that I used to take the image above:
About the Author
Maximilian Simson is a macro photographer based in London, Ontario. You can find more of his work and creative ideas on his website and YouTube channel, and follow him on Instagram and Facebook. This article was also published here and shared with permission.