How Do Cameras Work?

Marissa Schimpf

March 26, 2021

For the past year, talk of the COVID-19 pandemic has been inescapable, and I have only contributed to the Internet’s overwhelming amount of coronavirus-related media. While, of course, staying updated on this pandemic is crucial, I wanted to give the reader the opportunity to consume other scientific information. When trying to think of an interesting topic, I remembered the many Tik Toks I’ve seen of teenagers dumbfounded by today’s common technology, from speakers to cruise ships. I plan to explain how a piece of technology we take for granted– the camera– really functions. 

In the United States, around eighty percent of the population owns a smartphone, and that number grows constantly. Among the smartphone’s countless uses is the camera, meaning the majority of US citizens have easy access to a resource once considered revolutionary. Whether it be sending one’s daily Snapchat selfies or taking a panoramic photo of an amazing view, the camera has infiltrated our lives. However, I assume very few camera users know what happens when they take a photo of their brunch. I didn’t either, until a few weeks ago. 

Before examining the more complicated digital cameras such as that which is in your smartphone, we should start by talking about the historic film camera. You likely have heard of many of the most important parts of a camera, such as the shutter and lens. Essentially, a film camera can be compared to a one-story house with only one window, that window being the lens. On the back wall of this “house,” opposite the window, is a light-sensitive sort of paper covered by silver crystals. When photons (the energy particles associated with light) hit these crystals, they react with one another, and the crystals turn black, giving the impression that the paper itself is black. This “paper” is film. When light moves toward the camera, it passes through the lens and hits the film, which creates a photo! 

You must be wondering, “If light was constantly passing through this lens, wouldn’t all of the film just be black?” Good question! Yes, it would, and that is why the shutter exists. In keeping with the “house” analogy, the shutter of a camera is comparable to the curtain over the window or lens. The curtain, or shutter, is almost always closed– until you decide to take a photo. Then, it quickly opens, and the light travels through the lens or lenses (many cameras have a multi-lens system to improve the quality of the image) to meet the film. 

Additionally, inside the camera is a mirror that rests in front of the film when a photo is not being taken: the minute you take a picture, it flips away, allowing the film to soak up the light. The purpose of this mirror is to give the photographer an idea of what the photo will look like; the mirror reflects the image toward the top of the camera into a prism, which bounces the image around in a very complicated fashion (think of a mirror maze). Ultimately, the image is  projected into a small window so the user can see exactly what their camera lens is currently “seeing.”

Now you have officially read an oversimplified version of how the film camera functions. A digital camera, although much more technologically advanced, isn’t too much more challenging to comprehend. One major difference between a film camera and a digital camera is that a digital camera has a digital sensor, a flat, rectangular panel filled with millions of pixels, that can recognize light in place of film. When a photon of light hits one of the digital sensor’s pixels, the atoms in the pixel absorb the energy and eject an electron, which produces a negative charge. The more light that hits a certain area, the more electrons in that area, and the more concentrated the negative charge is in that area. A computer can detect this negative charge and use this information to produce a photo. A digital camera also has an electronic shutter, meaning that it can turn on and off the digital sensor whenever it needs to rather than physically covering it. Additionally, the digital camera lens can be shifted forward and backward electronically. Lastly, the camera has light sensors, which measure brightness, and a rangefinder, which measures the camera’s distance from objects in its frame. Needless to say, while some of this vocabulary may be familiar to you, the inner workings of digital cameras are much more complicated than those of film cameras.

I hope you have learned something new about the camera, a crucial feature of modern society yet a tool many do not deeply investigate. The next time you take a photo on your smartphone, you can say you have some semblance of an idea of how its technology works.