Sunday, 17 July 2011

Notes about light

I'm a beginner in the photography world. Since some days ago I've been watching some video-conferences about photography. They are a learning method made by José Benito Ruiz called "A year of photography", patronized by CAMON. 44 excellent sessions about photography (in Spanish).

Recently I've been studying the light. I'm physicist, so I know some things about light, but I've never studied the light in photography before. They are concepts new for me, and I would like write a brief note about I've learned.

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Types of Light

First of all: types of light. There are two types of light: hard and smooth.

  • Hard light: It produces hard shadows and a fast degradation (the way between white and black is very short).
  • Soft light: It produces smooth shadows. The degradation have a lot of middle tones (between black and white there are a lot of tones, and the transition is very progressive).

We have hard light when the apparent size of our source is much smaller than the object we are going to take the picture. When the source has a apparent size larger than the photographed object, we have soft light. We can have large sources when the light of a small source bounces in a large diffusive surface. The soft light have more details because it doesn't burn the scene.

Remember apparent size depends of the distance.


Direction

Different directions of the light have different effects. The light's direction is refer to the position of the camera. We have the below possibilities:

Gota a gota

  • Zenith light: It's the light from above the camera. It's natural, because we usually have the sun above us. It separates objects and background, because It defines the top of our silhouette.
  • Nadir light: It's when the light go from down to up. It is a unusual very dramatic light.
  • Frontal light: It's the light of our integrated flashes. It goes from the camera to the photographed object. It makes the object seems flat, without shadows. It enhances the colour but It destroys the depth.
  • Lateral light: It goes from left/right side to the opposite side. It produces a lot of shadows and It enhances the depth sensation.
  • Background light: It's when the light source is behind the object: the object is placed in middle, between the light source and the camera. It produces silhouettes and transparencies (when the object has transparent parts).

You can have middle cases between the above possibilities. You also can mix several light sources with different orientations.

Colour

The colour of the light is measured with the temp of colour. when a black body is heated, it emits electromagnetic radiation and its wavelength (the colour) depends of the temp.

Juncos reclamando la llegada de la primavera

Low temps (3000 K) are associated to low energies, i.e. long wavelengths (reds). High temps (8000 K) are for  large energies, i.e. short wavelengths (blues, violets).

The white balance is a camera attempt to force something to be white. When we set a white balance of 3000 K, we are telling to our camera that the scene is red, and the camera tries make it white: it applies a blue filter. If we set the white balance in 8000 K (blue), the camera applies a red filter.

When you mix several lights, you have to think in how they are going to be showed in your camera. The colour depends of the white balance. A yellow-red light (a hot light) can be white with a blue filter (cold white balance). When we take a picture there are lights that we can control (flashes, torch), but there are lights that we can't control (the sky illumination). We can change the sky's colour with the white balance, but all the scene will be showed with a colour filter, so we have to consider those filters when we are illuminating.

The coherence of all these qualities of the light is very important. We must know and use the light for build realistic scenes.

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