How Photographic Film Works

The Basics

­­What does it really mean when you “take” a picture with a camera? When you click the shutter, you have frozen a moment in time by recording the visible light reflected from the objects in the camera’s field of view. In order to do that, the reflected light causes a chemical change to the photographic film inside the camera. The chemical record is very stable, and can be subsequently developed, amplified and modified to produce a representation (a print) of that moment that you can put in your photo album or your wallet, or that can be reproduced millions of times in magazines, books and newspapers. You can even scan the photograph and put it on a Web site.

To understand the whole process, you’ll learn some of the science behind photography — exposing the image, processing the image, and producing a print of the image. It all starts with an understanding of the portion of the electromagnetic spectrum that human eyes are sensitive to: light.
How Photographic Film Work

Light and Energy

­Energy from the sun comes to the Earth in visible and invisible portions of the electromagnetic spectrum. Human eyes are sensitive to a small portion of that spectrum that includes the visible colors — from the longest visible wavelengths of light (red) to the shortest wavelengths (blue).
Microwaves, radio waves, infrared, and ultraviolet waves are portions of the invisible electromagnetic spectrum. We cannot see these portions of the spectrum with our eyes, but we have invented devices (radios, infrared detectors, ultraviolet dyes, etc.) that let us detect these portions as well.
Light is neither a wave nor a particle, but has properties of both. Light can be focused like a wave, but its energy is distributed in discrete packets called photons. The energy of each photon is inversely related to the wavelength of the light — blue light is the most energetic, while red light has the least energy per photon of exposure. Ultraviolet light (UV) is more energetic, but invisible to human eyes. Infrared light is also invisible, but if it is strong enough our skin detects it as heat.
It is the energy in each photon of light that causes a chemical change to the photographic detectors that are coated on the film. The process whereby electromagnetic energy causes chemical changes to matter is known as photochemistry. By carefully engineering materials, they can be chemically stable until they are exposed to radiation (light). Photochemistry comes in many different forms. For example, specially formulated plastics can be hardened (cured) by exposure to ultraviolet light, but exposure to visible light has no effect. When you get a sun tan, a photochemical reaction has caused the pigments in your skin to darken. Ultraviolet rays are particularly harmful to your skin because they are so energetic.

For more detail: How Photographic Film Works


About The Author

Ibrar Ayyub

I am an experienced technical writer holding a Master's degree in computer science from BZU Multan, Pakistan University. With a background spanning various industries, particularly in home automation and engineering, I have honed my skills in crafting clear and concise content. Proficient in leveraging infographics and diagrams, I strive to simplify complex concepts for readers. My strength lies in thorough research and presenting information in a structured and logical format.

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