Photopic Vision
Photopic Vision is the term for human colour vision under
normal lighting conditions during the day. In the range above
3.4 cd/m2, the human eye uses three types of cones to sense
light in three respective bands of colour. The pigments of
the cones have maximum absorption values at wavelengths of
about 445 nm (blue), 535 nm (green) & 575 nm (red). Their
sensitivity ranges overlap to provide continuous (but not
linear) vision throughout the visual spectrum. The maximum
efficacy is 683 lumens/W at a wavelength of 555 nm (yellow).
Mesopic Vision
Mesopic Vision Is the term for a combination between photopic
vision and scotopic vision in low but not quite dark lighting
situations. The combination of the higher total sensitivity
of the rods in the eye for the blue range with the colour
perception through the cones results in a very strong appearance
of bluish colours, like those in flowers, around dawn.
Scotopic Vision
Scotopic Vision is the term for human vision "in the
dark", below 0.034 lm/m2. In that range, the human eye
uses rods to sense light. Since the rods have a single absorption
maximum of about 1700 lumens/W at a wavelength of 507 nm,
scotopic vision is colour blind. The sensitivity range of
the rods makes the eye more sensitive to blue light at night,
while red light is almost exclusively perceived through photopic
vision.
Light Therapy
Light Therapy and treatment using light is being thoroughly
researched and pursued as a new and rapidly growing area of
study and application. Particularly when seeking to manage
circadian rhythm’s, proper and qualified instruction,
which is not available on this web site, should be taken.
Most likely the best light sources, for effect, peak at and
around 460nm, sometimes known as actinic blue.
As much as possible, light "treatment" should be
administered on an individual prescribed basis, we all have
differing needs and bio compatibilities. We certainly don't
claim an "All-in-One” solution from using sulphur
plasma lighting. However, until we work out how to pipe sunlight
to the dark side of Earth, we do our best to provide information
that will be useful and helpful.
Perhaps we should question the real usefulness of contemporary
measurements in Lumens (photopic brightness), Kelvin (colour
compared with heating Carbon), CRI (Rendering compared with
a Tungsten lamp from the previous millennium) and Lumens per
Watt (efficiency and efficacy are not the same). The relevance
of any measurement is very dependent upon the intended application
and the way the user interprets the meaning or significance
of the measurement or definition.
Much has been written about Continuous Full Spectrum Lighting
(CFSL), sadly, nearly all refers to using Fluorescent Mercury
or Metal Halide or Xeon lamps. Most articles written, even
by experts and professional practitioners, no matter if “For”
or “Against” CFSL, could not be much further from
the truth. All too often, they have never even seen sulphur
plasma light, they don’t know what it is and are quite
ignorant of Far Eastern research and practices taking place
during the last decade. |
