How the Eye Perceives Light

PHOTOPIC AND SCOTOPIC LIGHT

Luminous efficacy

Ellipz Lighting products are unique because they are manufactured with an understanding of how the human eye perceives light.

A short explanation might be in order:
The eye sensitivity curve V(λ) is based on measurement at photopic light level with a 2° view angle (faveal). (CIE standard 1931.)

Diagram 1 shows that our eye can see light from blue to deep red with the highest sensitivity in the green/yellow area.  1 Watt converted into light with 100% efficiency results in 683 lumen.

Diagram 2 shows that during the day (at Photopic light levels) our vision is the best at 555 nanometers. In the night (at Scotopic light levels) our visibility is best at 505 nanometers

Diagram 3 shows that the best day vision is at 555nm (Yellow – Green) and at night vision is at 505nm (Green – blue). With LED, light composition can be chosen with more accuracy than with conventional light sources, for instance: green at 509 nm (with 2 nm deviation). Light with a green component gives best sight in street lighting at minimum illumination levels: our visual perception mainly relies on our sensitive rods.

Studies have shown that the ratio between Scotopic (night) and Photopic (day) vision (so-called S/P ratio), is a base which can be used to multiply the lumen with the S/P ratio to express the real light perception and it also indicate how comfortable the atmosphere and the perceived brightness is.

The Hazards of Blue Light
 

Light of any kind can suppress the secretion of melatonin, but blue light does so more powerfully. Harvard researchers and their colleagues conducted an experiment comparing the effects of 6.5 hours of exposure to blue light to green light exposure of comparable brightness. The blue light suppressed melatonin for about twice as long as the green light and shifted circadian rhythms by twice as much. Many of us spend many hours per day under blue lights, including computer monitors. Is it any wonder our mood and sleep patterns are severely disrupted? Read more here about the Harvard Medical School Research on blue light.

Lens Damage
Lens yellowing is a natural occurrence. By the age of 20, the lens becomes a natural absorber of wavelengths between 400 and 320nm. The lens helps protect the retina from damage by near UV radiation and also provides partial but imperfect protection to the retina from blue light. In early studies it was thought that UV B was the only wavelength band responsible for cataracts.  

Young people under the age of 20, and especially very young children, have little or no yellowing of the lens. Therefore any UV or blue light that enters the eye is unfiltered and strikes the retina at full strength exposing not only the retina, but also the lens to damage.  Nancy Quinn, a registered nurse and an expert on blue light emissions wrote: “Blue light wavelengths and part of the blue spectrum are focused in front of the retina, while green and yellow are focused on the retina, and some red spectrum is focused behind. Thus blue light contributes little to visual acuity and visual perception loses sharpness as the blue light component adds significantly to the eye's energy expenditure for focusing, and if reduced can greatly reduce eye strain without loss of acuity." 1

Ellipz LED lights do not use blue diodes to create white light!
Using our knowledge of pupil control with high energetic wavelength light results in the choice of a combination of colors and as little as possible blue for optimal nighttime vision without damage to the eye or melatonin suppression.

• The eye is served with additional visual flux.
• The 498 nm peak sensitivity of the rods is closer to Cyan (505 nm) than to Blue (450 nm).
• The effect of blue on the eye is reduced by age but reduction is less with Cyan.

Strengths of Ellipz Technology
• Understanding the Spectral Power Distribution (SPD)
• Understanding the eye response with SPD
• Creating the highest S/P ratio at the black body curve
• Ellipz lights have the best color sensation
• Integrating cyan in standard white light (less blue light)
• Longest lifetime by color mix
• The result is high quality light (and a better night's sleep!)