Anyone who has a minimum of familiarity with photography knows full well that being able to recognise and fully master various types of light allows you to achieve entirely different images using the same subject and lens. So much so that these can go from being considered, depending on the circumstance, lovely to look at and pleasing to the eye or unpleasant and insignificant.
Here are two physical parameters that the quality of the light depends on, and which it's necessary to know how to interpret in order to achieve the images we desire:
- The direction of the source of light
- The temperature of the light
Incident light and reflected light
As regards the first parameter, first of all it is necessary to distinguish between incident light, that is, the type that strikes your subject, and indirect or reflected light, which instead reaches the scene after being modified by diffusion, reflection and filtering.
The example of a person's face photographed or filmed in strong summer sunshine and then on a cloudy autumn day is the most direct and easiest to understand, and it clarifies precisely what the difference is between the two types of light: in the first case, the image will have large areas of strong lighting contrasts, with sharp, dark shadows under the nose, the chin and the eyes, contrasting with much lighter areas that reflect a lot of light; in the second case, the face will instead be lit much more evenly.
Hard and Soft Lighting
Instead, what determines whether the light is incident or reflected is the distance and size of the light source.
When this is very small compared to its distance from the subject, incident light is produced, causing sharp, well-defined shadows (therefore three-dimensionality): this is the so-called hard lighting.
On the contrary, when the light source is large compared to its distance from the subject, the shadows it casts are softened and not clearly defined: in this case it's called soft lighting.
The sun, the natural light source par excellence, although huge, is located so far away from the Earth that we consider its rays as parallel and therefore generated by a point source. For this reason, its lighting is classed as hard.
The Earth's spinning and rotating movements, its atmosphere and the variability of weather conditions are, however, all factors that constantly intervene and change the quality of sunlight.
The influence of the first two manifests itself in the changing angles of the sun's rays with the optical axis of the lens, even if the position of the subject and the position you're shooting from do not change. To make this clear, try taking the exact same photo at 8.00 in the morning and at 8.00 in the evening; or at the same time but on July 15th and then on January 15th. And then compare the photos...
In order to find the angle of incidence that best suits your shooting requirements, it's clear that the quickest and most direct system is moving the camera rather than waiting for the change in seasons ... But, in any case, the most important thing to keep in mind is the fact that by increasing this angle (that is, going from an alligned or frontal light – a 0° angle of incidence – to the other extreme of against the light – 180°), an increasingly large area of the three-dimensional subject will be in shadow and, consequently, less and less of the subject will be directly illuminated.
Diffusion, instead, is caused by the atmosphere and the variability of the weather. A ray of light that passes through a translucent substance will clash with the particles contained in that substance and will be forced to "bounce" in every direction. Obviously, the higher the number of particles impeding the ray of light, the more this process will be increased.
The atmosphere of our planet in itself already diffuses light, but if we add to this conditions of heavy cloudiness (or heavy smog...), the end result will be the great diffusion of sunlight which, as it reaches every part, will not produce shadows on the subjects photographed and will therefore give rise to a feeling of "softness".
It's a little as if the entire sky above us acts as a huge light source.