As the social chairs, Sophie and Antonio are responsible for taking pictures during TV Club and posting them on their social media page. Sophie opens the camera app on her phone and asks Tania to take pictures of the group while they’re eating pizza and discussing the first episode of Finding Alyssa.
Converting Light into Data
When you take a photo with your phone, the lens of the camera focuses light onto the camera sensor. As continuous signals—like the gradual darkening of a shadow from its center to its edge or the slight variations in color caused by the wrinkles in a shirt—fall across the array of pixel sensors, each pixel sensor converts the light into values for red, green, and blue. The camera sensor then generates a large set of numbers (digital data) describing the values from all the pixel sensors.
Subject
The world is alive with analog signals: information that changes smoothly over time. When you hear sounds, you’re sensing continuous waves of changing pressure in the air around you. Your sight works by sensing light waves cast onto your retinas by the lenses in your eyes. But computers work with digital information: huge amounts of individual numbers. In order for computers to process analog signals, they have to digitize them—which involves converting them into a set of discrete values.
Camera Sensor
Digital photography is a good example of analog-to-digital conversion.
The camera sensor in a phone is a rectangle filled with tiny circuits that can measure the amount of light that hits them. Three circuits—one for each of the primary colors of red, green, and blue—are grouped together to make a pixel sensor. (“Pixel” is short for picture element.)
Digital Image
This process is called sampling. Computers convert analog signals to digital data by sampling them at discrete intervals to produce numbers. In this case, the intervals are the physical locations and dimensions of the pixel sensors, and the numbers represent colors and intensity of light.
The resulting information is an abstraction—an approximate representation of the real-world image that passed through the lens of the camera.
What Color is That?
Learn more about colors within an image.
Many of the images you see on your phone are compressed. Compressing an image doesn’t reduce the number of pixels (its resolution), it just reduces the data needed to store the image. Compressed images take less time to download and less space to store. How is compression possible? Compression strategies can be grouped into two broad categories: lossless and lossy. Lossless compression preserves all of the original data, so that it can be reconstructed at any time. Lossy compression creates an approximation of the original information, resulting in lower quality.
Lossless Compression
Watch this video and learn more about lossless compression.
Lossy Compression
Watch this video and learn more about lossy compression.
Using the shutter button, Tania captures a few great shots that are now saved to Sophie's photo roll on her phone. Sophie can’t wait to post them to social media after TV Club.
