Colour Science & Perception
what the eye settles, and what it cannot
Concept

Retinal position — where it appears

Where on the retina a stimulus lands, which decides how much macular pigment it passed through and how long a path it took through the cone outer segments. It is what a field size is a proxy for: the CIE's two standard observers differ because the fovea and the parafovea are two different filters, not because a large patch is looked at differently from a small one.

Named by 2 essays across one field — each of them below, with the objects they name alongside it.

The three cone absorptances at two settings of the field size. Solid and dashed are the same construction at the two ends of the CIE's own second observer. The curves are built from one pigment template through its ocular media, which is the same model its population of two hundred eyes is drawn from. The largest difference between the two sets is 16.0 per cent of the peak, and where it sits along the wavelength axis is what decides which stimuli the two observers disagree about — a departure concentrated in the blue is invisible on a sample with no blue in it.

A field size is two changes

The CIE publishes two standard observers and the difference between them is usually described as a field size. What actually differs is a macular pigment the light no longer passes through and a cone outer segment the light no longer travels the length of — two changes, in two places, with different signs and different sample dependence.

eye · Cones The three cone absorptances at two settings of the macular pigment. Solid and dashed are the same construction at the two ends of two standard deviations of the reported spread. The curves are built from one pigment template through its ocular media, which is the same model its population of two hundred eyes is drawn from. The largest difference between the two sets is 31.5 per cent of the peak, and where it sits along the wavelength axis is what decides which stimuli the two observers disagree about — a departure concentrated in the blue is invisible on a sample with no blue in it.

The macular is a band, not a filter

The lens absorbs everything below 500 nanometres with a long tail; the macular pigment absorbs forty nanometres either side of 460 and nothing else. The two have similar sizes and completely different distributions, and the reason is that one is broad and one is narrow — which is what decides whether a sample is affected at all.

eye · Cones

Named alongside it

The objects these essays reach for when they reach for this one.

EccentricityIndividual variationMacular pigmentStandard observerCone fundamentalsLuminaireObserver metamerismOptical densitySelf-screeningSpecificationSpectral structureStructural choice

All concepts