enricosavazzi wrote:
I would not exclude the possibility that the observed phenomenon is in part caused by axial chromatic aberration of the lens. If the lens displays this type of chromatic aberration, it focuses red and green (or often green and purple) on slightly different planes.
A possibility. The objective lens is a Olympus UMPlanFl 10X/.3NA. I use a Pentax 200mm telephoto as the prime. I do not observe axial chromatic aberration on other subjects.
enricosavazzi also wrote
Then there is also a possibility that the lenses of the ommatidia produce axial chromatic aberration, which would give the observed result.
General thinking is that the eye color results from multi layer interference filters on the cornea of the ommatidium lens, and that the reflected light is colored by differentials between the filters on the surface. I think this would be in front of the refractive errors of the lens.
A PDF of Miller and Bernard's paper on corneal interference filters can be downloaded here...
http://iovs.arvojournals.org/article.as ... id=2166697
enricosavazzi also wrote
A third possibility is that the orange and green ommatidia are structurally different and have similar internal structures but placed at different depths (which by the way might also be an adaptation to compensate for different axial chromatic aberration in the two types of ommatidia).
I think that there may be structural differences also. I have not figured out exactly what they may be. Some critters use colored liquids in their eyes to provide color filters for the optical sensors. I am starting to wonder if that may be the case here also.
Another possibility is that this is a "blur" phenomena. I notice in the stacked images that the "green" ommatidium look more yellow with a blue border. Perhaps the out of focus green is a combo of the blue border with the yellow center. I may be able to laser print a test subject with yellow centers and blue borders and try some experiments...
Keith
