Page 18 - NyghtVision Boot Camp One Fill Edition

Question Three: What time is it?
By knowing what day it is (the answer to question
one), we know - or can estimate - the total hours of
light we will have in a given day. By knowing what
time it is, we can easily determine how much light is
left. As we shall see when we talk about question four,
this in turn will enable us to “fine tune” our unders-
tanding of light when we are working.
Question Four: What is the angle, direction,
and intensity of light?
Lets talk about the direction of light first. The earth
moves from east to west over the course of a day. In
the Northern Hemisphere, the sun follows the equa-
tor. This means sun never passes through the Nor-
thern Quadrant. In the Southern Hemisphere, the
sun never passes through the Southern Quadrant.
So, how can you determine where north is in
the Northern Hemisphere? There are two ways:
18 Boot Camp, Part 1
v Look at the shadows. In the Northern Hemisphere,
shadows point toward the north. In the Southen Hemis-
phere, the opposite is true.
v Also, look for moss or lichen on a tree near the ground.
Moss and liken generally grow away from the path of the
sun - in the Northern Hemisphere that would be north.
The angle of light is a function of the day of the year, the
location (longitude/latitude/altitude), and time of day.
(See diagram on the next page.)
The best way to understand the concept of the inten-
sity of light is to think of it in reverse terms: The more
diffuse the light, the lower its intensity. When the in-
tensity of light is high, the edges of shadows are sharp
and “clean.” Intense light can be a very serious problem
since as we shall see it can bleach color from an image
and can make shadows extremely dark and loss of detail
in brighter areas is a common problem.