Exploring Light in London: The Science Behind Sun, Shadow, Fog and Rain

Light Behavior in Sun and Shadow

The interaction of sunlight with the Earth’s atmosphere and surfaces creates a variety of optical phenomena. The angle at which the sun illuminates an object, known as its altitude, determines the length and direction of shadows cast by that object. Using the equation L = h / tan(alt), where L is the shadow length, h is the height of the object, and alt is the solar altitude, one can calculate how long a shadow will be at any given time and date.

Understanding these principles helps in predicting and interpreting shadows in different weather conditions. For instance, during fog or rain, light scattering changes, affecting both the visibility and the appearance of shadows.

Fresnel Mirrors: Rain's Refractive Effects

Raindrops act as tiny prisms, refracting sunlight into a spectrum of colors. This phenomenon is known as dispersion. When light passes through raindrops, it bends (refracts) and splits into its constituent wavelengths, creating the familiar rainbow effect. In the simulation, you can observe how different angles of incidence affect this refraction, turning wet streets into natural spectacles.

The intensity and visibility of these effects depend on the angle at which light hits the raindrops and the observer’s position relative to them.

Koschmieder Fog: Dimming the Skyline

Fog, particularly when dense, can significantly reduce visibility by scattering light. The Koschmieder law quantifies this effect, stating that the extinction coefficient of fog is proportional to the fourth power of its density. This means that as fog becomes denser, it absorbs and scatters more light, effectively dimming the surroundings.

In the simulation, you can adjust the fog density to see how it impacts the visibility and brightness of distant landmarks.

Balancing Exposure: Aperture, Shutter Speed, and ISO

Photography involves balancing three key elements: aperture (the size of the lens opening), shutter speed (how long the camera’s sensor is exposed to light), and ISO (sensitivity of the sensor). The exposure value (EV) combines these factors into a single number, making it easier to adjust settings for different lighting conditions. In the simulation, you can manipulate these variables to achieve the perfect exposure in various weather scenarios.

For example, on a foggy day with low light, increasing the ISO and slowing down the shutter speed might be necessary to capture clear images.

Frequently asked questions

Try it live

Everything above runs in your browser — open London Landmarks Photo Quest: Sun, Shadow, Fog and Rain Light and change the parameters while it is running. Nothing is installed, nothing is uploaded, the whole model lives in one tab.