Ocular media transmittance doesn't seem to get much attention. Most researchers (myself included) simply ignore it when simulating the PSF of the eye for example. This assumes that the eye has 100-percent transmittance which is clearly not true. I recently came across a plot of transmission spectra; it can be found on page 9 of "Field Guide to Visual and Ophthalmic Optics" by Jim Schwiegerling. Upon some closer scrutiny, it just seems very hard to believe that only about 50-percent of the light (around green so 550 nm or so) incident on the cornea makes it to the retina. Is a typical healthy eye that un-transparent? There seems to be very little rigorous work on this subject. The only paper I can really find is that of Boettner and Wolter published in 1962 in IOVS. I think we should pay more attention to this topic and require its incorporation in our models.
Dear Kaccie Yiang Li
In reply to your suggestion, I start from the response to light stimuli in human colour vision; which has been shown to be characteristically three-dimensional. And that it may thus be successfully modelled by means of three broad band (R G and B) sensor-response functions. The above additive sum is successfully modelled with worldwide acceptance in ‘CIE Standard Observer Tristimulus Colorimetry’ , thus enabling the design and production of coloured products. It follows that the spectral detail you refer to is obscured by additive sum in the human visual response. Many individual combinations of these spectral components thus generate the same additive product and therefore look exactly the same colour. The result is a valuable genetically evolved simplication of our senses that allows us to analyse, colour match and assess the possibility of danger in our visual surroundings or perhaps locate some edible food.
The individual members of the above sets of visually identical colours have distinct Spectral Power Distributions (or SPDs); they are referred to as ‘metamers’; and the visual property thus characterised is referred to as ‘metamerism’. The study of metameric or ‘conditional’ visual equivalence is a complex but well-studied topic in Colour Science, see if you will Google Scholar using the key "metameric visual equivalence".
David Oulton - you're talking about visual sensitivity which is at the retinal level and beyond. The discussion here is purely optical through each refractive (and a bit scattering media) and have almost nothing to do with CIE curves. Please reread carefully...@
modern sources show a much higher transmittance, yet measured in rabbits and not humans.
it seems there is large differences from cadaver to living eyes:
Article Measurement of transmission of ultraviolet and visible light...
https://iovs.arvojournals.org/article.aspx?articleid=2179100
further if you carefully read Better and Wolter you see they also find >80-85% for the visible spectrum
http://ec.europa.eu/health/scientific_committees/scheer/docs/sunbeds_co240n_en.pdf
http://contrails.iit.edu/reports/7448
https://apps.dtic.mil/dtic/tr/fulltext/u2/663246.pdf
Chapter Human Vision and Perception
The assumption is not of 100% transmittance, it is an assumption of spectral constancy that is a metameric property of an an essentially three dimensional response. As described above and in some detail in my Nov 2016 RG post.
David, what you're saying I'm sure is applicable to vision, but I still don't what it has to do with my post. Nobody's talking about the retina here (and definitely not visual sensitivity) - I'm just addressing the refractive components of the eye from cornea to vitreous. Please stop posting irrelevant comments. David Oulton
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