Are there four, six, or seven unique hues? by Christopher W. Tyler

Supplementary Material
The colors visible in the color circle are shown in the upper part of Fig. 1. The left-hand image shows the standard color circle, in which yellow, magenta and cyan colors appear as narrow ridges between large spans of red, green, and blue. When the whole image is pushed through a compressive nonlinearity (right-hand image), the color ratios change dramatically, with the yellow, magenta, and cyan zones expanding to become at least as wide as the red, green, and blue ones. This reconfiguration supports the concept of six fundamental, or unique, hues, consistent with the prediction of the complementary color system based on the three cone classes and their complements (see Pridmore, 2013, for a review of the neurophysiological support for this analysis).

Fig 1. Two versions of the color circle, with test disks for viewing their afterimages. View as close as possible for optimal effect

Fig. 1. Two versions of the color circle, with test disks for viewing their afterimages. View as close as possible for optimal effect

To view the afterimage colors, one black dot should be fixated for 10-20 seconds, and fixation then transferred to the center disk. It will be seen that the afterimage that appears emphasizes the cyan, yellow and magenta colors across the circle diameter (as shown by the data in Fig. 2), even for the Standard linear color circle but more strongly for the Compressive one. This demo validates that the complementary pairings are not red vs green, but red vs cyan (aqua), and green vs magenta (purple), consistent with the concept of 6 fundamental colors around the color circle.
Data for one subject with strong afterimages

Fig. 2. Data for one subject with strong afterimages, showing that tight adherence to the complementary direction in CIE space, passing through neutral gray (not the yellow neutral point of red-green opponency). Black circles: loci of the adapting stimuli. White circles: afterimage loci, connected to the respective adapting loci with white lines. Triangle: monitor color gamut.

 

Reference
Pridmore, RW (2013) Single cell spectrally opposed responses: opponent colours or complementary colours? J Optics 42: 8–18.

Now Online: Was Leonardo da Vinci’s World Map the First to Name America?

Was Leonardo da Vinci’s World Map the First to Name America? A Quincentennial Reappraisal

Leonardo da Vinci’s World Map, image

Abstract
In addition to his better known artistic, scientific and engineering talents, Leonardo da Vinci has an extensive reputation as a cartographer, drawing maps for a wide range of hydro-engineering projects for the rulers of Florence, Milan, Arezzo and the Vatican, amongst others. However, he is not generally acknowledged as authoring a world map (or mappamundi) spanning the globe, which was the domain of a few specialized cartographers of the era. Nevertheless, there is a world map among his papers in the Royal Library, Windsor, which has the correct overall configuration of the continents, including an ocean at the north pole and a continent at the south pole. Moreover, it has a unique cartographic projection onto eight spherical-geometry triangles that provide close to isometric projection throughout the globe.

This quincentennial anniversary year of his death in 1519 is an appropriate moment for a reappraisal of this contribution to global cartography. Although the authenticity of this world map has been questioned, there is an obscure page of his notebooks in the Codex Atlanticus containing a sketch of this precise form of global projection, tying him securely to its genesis. Moreover, the same notebook page contains sketches of eight other global projections known at that time (early C16th), from the Roman Ptolomaic conic section projection to Rossellli’s (1508) oval planispheric projection. This paper reassesses the dating of Da Vinci’s unique mappamundi to suggest that it predates that of Waldseemüller (1507), and may thus have been the first map to name both America and Florida.

Citation:
Tyler, CW. 2019. “Was Leonardo da Vinci’s World Map the First to Name America? A Quincentennial Reappraisal,” Calafia Journal, 2:7-12. PDF

Lecture: Was Leonardo da Vinci’s World Map the First to Name America?

Was Leonardo da Vinci’s World Map the First to Name America?

by: Christopher W. Tyler, Ph.D., D.Sc.  –  Saturday Sept 28 @ 3:00 PM

Christopher Tyler’s scientific interests are in visual perception and visual neuroscience. With regards to Leonardo da Vinci, Tyler’s interests extend from his youthful activities as an extempore singer and artist’s model in Florence to his architectural and anamorphic influences in the Court of Renaissance France.

image+%281%29.jpgIn addition to his better known artistic, scientific and engineering talents, Leonardo da Vinci has an extensive reputation as a cartographer, drawing maps for a wide range of hydro-engineering projects for the rulers of Florence, Milan, Arezzo and the Vatican, amongst others. However, he is not generally acknowledged as authoring a world map (or mappamundi) spanning the globe, which was the domain of a few specialized cartographers of the era. Nevertheless, there is a world map among his papers in the Royal Library, Windsor, which has the correct overall configuration of the continents, including an ocean at the north pole and a continent at the south pole. Moreover, it has a unique cartographic projection onto eight spherical-geometry triangles that provide close to isometric projection throughout the globe.

This quincentennial anniversary year of his death in 1519 is an appropriate moment for a reappraisal of this contribution to global cartography. Although the authenticity of this world map has been questioned, there is an obscure page of his notebooks in the Codex Atlanticus containing a sketch of this precise form of global projection, tying him securely to its genesis. Moreover, the same notebook page contains sketches of eight other global projections known at that time (early C16th), from the Roman Ptolemaic conic section projection to Rosselli’s (1508) oval planispheric projection. This paper reassesses the dating of Da Vinci’s unique mappamundi to suggest that it predates that of Waldseemüller (1507), and may thus have been the first map in history to name both America and Florida.

Selected Press for Eye centring in selfies posted on Instagram

MedicalResearch.com:
Interview

News 18:
More to the Art: Instagram Users Focus on Centre of Left Eye in Selfies, Says Study

Science Daily:
Do we tend to centre our Instagram selfies on our left eye?

AAAS EurekAlert!:
Do we tend to center our Instagram selfies on our left eye?

LiveMint:
Instagram users tend to snap selfies that centre on left eye.

News-Medical.net:
Eye-centring common in ‘selfie’ photos

University of Liverpool:
Do we tend to centre our Instagram selfies on our left eye?

Daily Mail:
Why selfies usually focus on our left eye: Asymmetry in the brain makes people’s right side less dominant in most Instagram photos, study claims”

Elmundo:
Un estudio explica por qué los selfies se suelen centrar en el ojo izquierdo

 

 

Recent Studies Updates

2019

Eye centring in selfies posted on Instagram. PLoS ONE 14(7): e0218663. (with N Bruno and M Bertamini) PDF (also see MedicalResearch.com interview here

Evidence that Leonardo da Vinci had Strabismus. JAMA Ophthalmol. Jan 1;137(1):82-86, 2019.  PDF (also see links to article coverage.)

Points of contact between the Stappian philosophy and Emergent Aspect Dualism. Activitas Nervosa Superior, 81:1-6, 2019.  PDF

2018

The emergent aspect dualism view of quantum physics: a new ontology to resolve the complementarity conundrum. J Res Phil Hist 1:166–182, 2018. PDF 

Development and validation of a new glaucoma screening test using temporally modulated flicker. 
Ophthalmic Physiol Opt. 38:617-628, 2018. (with Fidalgo BR, Jindal A, Ctori I, Lawrenson JG.) PDF

A Brücke-Bartley effect for contrast. Roy Soc Open Sci. 5:180171, 2018. eCollection 2018. (with Solomon JA) PDF

Rational approaches to correcting for multiple tests. Human Vision and Electronic Imaging (535) 1-8, 2018. PDF