The light
All light is formed by many
different waves but only a very few of them are visible to humans.
The ligh sprectrum:
Radio----Microwave------Infrared------Visible
light-----Ultraviolet-----x-ray-----Gamma rayor by using image processing
software.
---------long
wave length-----------------------------------------short wave
length-----------------
---------low
frequency--------------------------------------------high
frequency---------------------
---------low
energy------------------------------------------------high
energy------------------------
Ulraviolet
light can affect film and digital sensors.
Infrared
light can be used for creative photographic effects, it’s possible by fixing an
opaque filter front of Lens.
UV Filter block the uv light
which although invisible for human is
recorded by photographic colour film and less so by digital sensors. Uv light
is most prevalent at high attitude and by the coast and causes an excessive
blue colour cast.
The colour temperature varies throughout
the day from warm reds and oranges in the early morning and late afternoon
trough to cold blues around noon. Like sunrise: red, early am:red, mid am:
yellow, late am:blue, noon: clear, early pm:blue, mid pm:yellow, laepm”red,
sunset:red.
The
light effects
The intensity of light depends on
the distance between the light source and he subject and the size of the light
source. The close the light source is to the subject the greater of
illumination. A direct light source produce harder, more intense light than a
larger light source, which typically produces softer, less intense lighting.
Natural lighting is harder to
control than artificial one but you can alter the size of the light source by
using natural diffusers such as clouds or artificial diffusers. The inverse
square law is a mathematical equation to measure the effect of changing the
light to subject distance. When halving the distance between the light and the
subject the level of illumination quadruples. The quality of light refers to
how hard or soft the light is. When light is from an unobstructed point source
referred to hard lighting as it produces a greater degree of contrast and
well-defined hard-edged shadows. When the light is diffused it produce les
contrast in the scene and less well defined shadows with softer edges. The direction
from which light falls on a subject will determine where and if shadows appear.
Side lighting is less suitable for revealing detail in therefore it’s typically
used for portrait, is often considered the best direction for lighting and
should be used when you want to reveal form or depth, also it’s the best for
creating landscape images with three-dimensional appearance. .Front lighting is
more suitable when photographing a building for revealing details, for record purposes.
Backlighting will produce silhouettes exposing for the highlights or will
produce rim lighting exposing for the shadows. Backlight is ideal for creating
atmospheric images of subjects such as people, animals ,landscapes.
The light
meters and exposure
The camera has a light meter, a
through-the-lens (TTL) meter, which mesure the intensity of reflected light
entering in the lens. It is calibrated to see everything in the world as 18%
grey and will provide an exposure calculation based on the subject being 18%
grey whether it is or it isn’t. For example when photographing snow using auto exposure function it will
typically appear grey in the final
image, because the camera thinks snow is 18% grey. The manufacturer had to set
a line in the sand, so 18% - medium-tone is exactly the half way between film’s
ability to record detail in shadows and highlights. When the subject is medium-tone then the
camera will produce a technically accurate exposure. However if the subject is
lighter or darker then the camera is liable to under-expose(lighter subject) or
over-expose(darker subject) because it is always trying to archieve a
medium-tone, 18% grey result.
Film and digital sensors have
limited ability to record detail across a broad range of brightness.
------------------------------------digital
sensor
----------------------------
negative film
--------------------
positive film
The TTL light meter can be set by
measuring the level of brightness in different sections of the viewfinder
screen to assess, the multi-segment is ideal to spend little time about
exposure, the centre-weighted metering calculate an exposure value(about75%)
from the centre circle, is considered ideal for portrait when the subject fills
the centre of the frame and the background plays a less significant role in the
composition. Spot-metering mesure the intensity of light from a tiny area
usually 3-5% and is used when calculating the difference in stops between the
lightest and darkest areas of the scene, typical for landscape.
Therefore exposure compensation
can be used as snow is around two stops brighter than medium tone by applying
+2 EV(exposure value) he camera will add 2 stops extra brightness to the scene.
The
Lighting ration
refer to the level of contrast and are a
measure of the difference in stops between the brightness of the shadows areas
compared to the highlights. Ex: a model lit on her left side by a direct light
and on her right side by a soft light then the lighting ration si 2:1. This
will help to visualize exactly the strength of shadows in the final image.
