Selective yellow

From Wikipedia, the free encyclopedia

Selective yellow (desaturated approximation)
— Color coordinates —
Hex triplet		#FFBA00
RGB^a	(r, g, b)	(255, 186, 0)
HSV	(h, s, v)	(44°, 100%, 100%)
a: Normalized to [0–255] (byte)

Selective yellow is a colour for automotive lamps. Under UNECE Regulations, headlamps were formerly permitted to be either white or selective yellow — in France, selective yellow was mandatory until 1993.

Current UNECE Regulations require headlamps to be white. However, selective yellow front fog lamps are still permitted.

The intent of selective yellow is to improve vision by removing shorter, blue wavelengths from the projected light, as these wavelengths are difficult for the human visual system to process properly, as well as causing perceived dazzle effects in rain, fog and snow and problems with glare.

[edit] Formal definition

The UNECE Regulations formally define selective yellow in terms of the CIE 1931 color space as follows:

Limit towards red	$y \ge 0.138 + 0.580 x$
Limit towards green	$y \le 1.290 x - 0.100$
Limit towards white	$y \ge 0.966 - x$
Limit towards spectral value	$y \le 0.992 - x$

For front fog lamps, the limit towards white is extended:

Limit towards white	$y \ge 0.940 - x$
	$y \ge 0.440$

There are currently competing proposals before UNECE to redefine selective yellow to include this extended range, and to eliminate selective yellow altogether from all lighting regulations.

The entirety of the basic selective yellow definition lies outside the gamut of the sRGB color space — such a pure yellow cannot be represented using RGB primaries. The color swatch above is a desaturated approximation, created by taking the centroid of the standard selective yellow definition at (0.502, 0.477) and moving it towards the D65 white point, until it meets the sRGB gamut triangle at (0.478, 0.458).

Here are images of a race car equipped with selective yellow headlamps and driving lamps, a set of fog lamps designed to produce selective yellow light, and of the light beam emitted from the same lamps:

[edit] References

[edit] External link

What is Selective-Yellow Light?

				Shades of yellow
Amber	Beige	Buff	Corn	Cream	Dark Goldenrod	Ecru	Flax	Gamboge	Golden

Goldenrod	Khaki	Lemon	Lemon Cream	Lime	Mustard	Navajo white	Old Gold	Olive	Papaya whip

Peach-yellow	Pear	Saffron	School bus yellow	Selective yellow	Tangerine yellow	Yellow	Apricot	Metallic Gold	Chartreuse yellow

Golden yellow	Golden poppy	Green-yellow