03Lecture

 

03Lecture / Week Three (print this document)

 

 

TECHNICAL

 

COMPONENTS OF LIGHT

 

There are three BASIC COMPONENTS OF LIGHT we will study in this class.  [click in the link for definitions]

 

  1. Specular Highlight
  2. Diffused Highlight
  3. Shadow

 

There are two basic QUALITIES OF LIGHT we will learn to identify.

 

1.     Specular Light (sunny day); also called Hard Light.  Characterized by hard shadow-edges transfers. 

1.    This light source is small in relationship to the subject (ex: the sun on a cloudless day is very small in relationship to the subject).

2.     Diffused Light (overcast sky); also called Soft Light.  Characterized by soft shadow-edge transfers.

1.    This light source is large in relationship to the subject (ex: an overcast sky; the entire sky is the size of the source).

3.     THE PRIMARY COMPONENT THAT DICTATES QUALITY OF LIGHT IS THE SIZE OF THE SOURCE IN RELATIONSHIP TO THE SUBJECT.

1.    The largest light source you will ever use is the SUN; but because it is so far away, it is small in relationship to the subjects you are photographing and is therefore a very specular light source casting very hard shadows.

2.    A relatively small source of light is a portable flash unit that fits in the palm of your hand; but if it is very close to a subject (like the flash unit your dentist uses to photograph inside your mouth), it will be large in relationship to the subject and therefore very diffused and cast very soft shadows or produce no shadows at all.

 

We use RATIOS to compare the difference between highlights and shadow. To hold detail in photographs in both highlights and shadows there must be no greater than 3 stops difference between these two values. We need to understand what film sees vs. what our eyes can see in order to control visible detail within our images.

 

  1. A 1 stop difference between highlight and shadow is called a 1:2 RATIO which means the shadow is 1/2 as intense as the highlight; or inversely, that the highlight is two times more intense than the shadow.
  2. A 2 stop difference between highlight and shadow is called a 1:4 RATIO which means the shadow is 1/4 as intense as the highlight; or inversely, that the highlight is 4 times more intense than the shadow.
  3. A 3 stop difference between highlight and shadow is called a 1:8 RATIO which means the shadow is 1/8 as intense as the highlight; or inversely, that the highlight is 8 times more intense than the shadow.
  4. More than 3 stops difference is called a 1:8+ RATIO.
  5. A heavily overcast day presents a diffused light quality which is described as a 1:1 RATIO.  In this light condition there are no shadows cast and the light is very even and flat.
  6. When exposure is based on the highlight, a 1:8+ ratio will have no visible detail in the shadows even though our eyes can easily see detail in the scene. 
  7. Open shade on a bright sunny day is typically 3 stops less light in the shadows.  There will be detail but just barely.  Think how well you can see into the shadows in open shade and examine how visible they appear on film.  It is quite different.

 

Additional Information:

  1. A bright sunny day presents a specular light quality and a ratio of 1:8.
  2. A light overcast can have sunlight visible through the overcast.   This condition will cast light shadows.  This condition could be described as somewhat specular since it casts a shadow, but probably would be considered more diffused than specular in nature.
  3. A cloudy day will present both qualities, specular and diffused, as the sun passes behind clouds and emerges again.   Exposures will have to change rapidly to accommodate the different amounts of light energy.  These are good times to rely on our automatic exposure features built into most of our cameras.

 

There are three KEYS OF LIGHT we will learn to identify.

 

  1. High Key Photographs ­ when the subject and background are predominantly light pastel or white color values.
  2. Low Key Photographs­ when the subject and background are predominantly dark or black color values.
  3. Normal Key Photographs­ everything else.

 

 

 

DIGITAL

 

THE BASIC ELEMENTS

Just as all photography is based on a factor of 2, all digital information is based on 0ıs and 1ıs.