[L01] Light

photography literally means “to write light”
so, it only makes sense to start photography by understanding what light is, who is making the writing happen and what’s writing the light.

from a physics standpoint, light is a bit of a split personality if you will.
one avatar of light is that of a wave, with alternating electric and magnetic waves perpendicular to each other propagating through space
light, alternatively, can be teated as a sea of photons, which are little packets of energy
- this split-persona of light is called wave-particle duality
the speed at which light travels is the fastest anything in known existence can travel
- as it travels through space, it slows down in the medium it travels in
- when it collides with objects, it gets reflected from, or absorbed by them

from a living organism’s standpoint
- an optimal amount of light is necessary to observe its environment for survival
from the standpoint of a living organism that wants to take pictures with a camera
- light is necessary to illuminate the scene of photographic interest
from a camera’s standpoint
- light is the signal that it’s sensor captures and stores

human vision can see over a large range of brightness magnitude
- from very dark conditions of a new moon (scotopic)
- to the bright sunlight of the noon (photopic)
- and everything in between (mesopic)
this range spans 12 log magnitudes of brightness
- achieved by using rods and cones together
photoreceptors in the human eye are of two types
- rods
- cones
rods are for dim light conditions (scotopic)
cones are for bright conditions (photopic)
there is an overlap for mesopic conditions in both rods and cones

rods are extremely sensitive to light
- there is one (1) type of rod
rods do not aid in color perception
rods gather light from a larger field of the visual domain
- rods are for low light and broad picture vision

cones are less sensitive than rods to light
- in humans there are three (3) types of cones
- each has a preferred wavelength of light that it responds maximally to
- this enables colors to be perceived
cones enable color perception
under photopic conditions, we see vibrant colors
under mesopic conditions, we see muted colors
cones gather light from a small field
- cones are for focussed, bright light vision with fine details