Re: Colorimeters and third-party developer support
Re: Colorimeters and third-party developer support
- Subject: Re: Colorimeters and third-party developer support
- From: Bob Frost <email@hidden>
- Date: Tue, 23 Aug 2011 11:00:02 +0100
- Importance: Normal
Yes, they are being very loose and sloppy, to make their case seem
more impressive - typical marketing stuff.
The actual case of course is that our color vision varies with
the location on our retina. The central part has all the color
detectors, and the periphery has the low light, monochrome detectors
that have a different spectral response to the other three. Hence
the change in CMF's with different areas of interest (2 degree vs. 10
degree).
Hi Graeme,
You seem to be a "bit loose and sloppy" yourself with your statement on the
distribution of the color detectors (cones) and monochrome detectors (rods).
;-
Both types of photoreceptor are found throughout the retina, except for a
very small area at the centre of the fovea - the foveal pit - which is only
about 200 microns in diameter. That does just contain cones. Outside that
small area the rest of the macula (6 mm diameter) and the 'periphery' (which
is actually the bulk of the retina up to 22mm diameter) contains a mixture
of rods and cones in varying numbers. The macula/foveal area contains mainly
cones, while the rod distribution peaks at about 4.5mm (18 degrees) off
centre - around the edge of the macula/foveal area. Cones may make up about
5% of the receptors in the outer areas of the retina.
Strangely, the distribution of the three types of cones (L, M, and S) varies
considerably. S-cones for example, seem to make up only 3-5% of the foveal
pit cones, reach 15% in the rest of the fovea, and 8% throughout the
'periphery' of the retina.
So, although a '2 degree calculation' does coincide with the central foveal
pit, that area is mainly M- and L-cones, with more S-cones outside this
2-degree area. I wonder what effect this has on our color vision?
Bob Frost
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From: "Graeme Gill" <email@hidden>
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