Since that first camera did not capture very much light, it actually took eight hours to take a single photograph. The image was also quite blurry. So how are we able to take sharp images in milliseconds today? A camera lens.
While light bounces off of objects, it can also pass through objects — but, when it does, it can actually change direction. A camera lens takes all the light rays bouncing around and uses glass to redirect them to a single point, creating a sharp image.
When all of those light rays meet back together on a digital camera sensor or a piece of film, they create a sharp image. If the light doesn’t meet at the right point, the image will look blurry or out-of-focus. A lens’s focusing system moves the glass piece closer or farther from the sensor or film, allowing the photographer to adjust the lens so that the object is sharp.
Distance also plays a role in how camera lenses are able to zoom in. When the front piece of glass moves farther away from the camera sensor, objects become closer. The focal length is the measurement of the distance between where the light rays first hit the lens and where they reach the camera sensor. For example, on a lens with a 300mm focal length, the light takes 300 mm to be directed back into a sharp point on the camera sensor. A 300mm lens is considered a telephoto, or a lens that’s able to bring far objects to close.
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