Photography, an art form that captures moments in time, is intrinsically linked with the principles of physics. Understanding the science behind how light behaves and how motion is captured can enhance your photographic skills and appreciation of this art. In this blog, we will explore the fascinating intersection of physics and photography, focusing on the behaviour of light and the techniques used to capture motion.
The Science of Light
At its core, photography is about capturing light. Light behaves both as a wave and as a particle, a concept known as wave-particle duality. This dual nature of light is fundamental to photography.
When light strikes an object, it can be absorbed, reflected, or transmitted. The light that is reflected from the object enters the camera lens, where it is focused onto a light-sensitive medium, such as film or a digital sensor. The sensor then converts the light into an image.
Reflection and Refraction
Reflection and refraction are two key principles of light behaviour in photography. Reflection occurs when light bounces off a surface. The angle at which the light hits the surface (angle of incidence) equals the angle at which it bounces off (angle of reflection). This principle is used in composing photographs, especially when dealing with mirrors or water surfaces.
Refraction, on the other hand, occurs when light passes from one medium to another, changing its speed and bending in the process. This principle is essential in lens design. Lenses are crafted to bend light in precise ways, focusing it onto the camera sensor to create sharp images.
The Role of Aperture and Shutter Speed
Two critical settings in photography that leverage physics are aperture and shutter speed.
Aperture refers to the opening in a lens through which light enters the camera. It is measured in f-stops (e.g., f/2.8, f/4, f/8). A larger aperture (small f-stop number) allows more light to enter, which is useful in low-light conditions. A smaller aperture (large f-stop number) allows less light, which is beneficial for achieving greater depth of field, keeping more of the image in focus.
Shutter speed controls the duration that light is allowed to hit the camera sensor. Measured in seconds or fractions of a second (e.g., 1/1000s, 1/60s, 1s), faster shutter speeds freeze motion, while slower shutter speeds can create motion blur, capturing the flow of movement in a scene.
Capturing Motion
Capturing motion in photography involves understanding the relationship between shutter speed and the movement of the subject. Fast-moving subjects require a fast shutter speed to freeze the action, while slower shutter speeds can be used to convey a sense of motion.
One technique to capture motion is panning. This involves moving the camera along with the subject’s movement while using a slower shutter speed. The result is a sharp subject with a blurred background, emphasising the motion.
Another technique is long exposure photography, where the camera’s shutter is left open for an extended period. This is often used to capture the motion of stars in the night sky (star trails), flowing water, or light trails from moving vehicles.