How Light Works
A digital camera takes light and focuses it via the lens onto a sensor made out of silicon. It is made up of a grid of tiny photo sites that are sensitive to light. Each photo site is usually called a pixel, a contraction of "picture element". There are millions of these individual pixels in the sensor of a DSLR camera.
Digital cameras sample light from our world, or outer space, spatially, tonally and by time. Spatial sampling means the angle of view that the camera sees is broken down into the rectangular grid of pixels. Tonal sampling means the continuously varying tones of brightness in nature are broken down into individual discrete steps of tone. If there are enough samples, both spatially and tonally, we perceive it as faithful representation of the original scene. Time sampling means we make an exposure of a given duration.
Digital cameras sample light from our world, or outer space, spatially, tonally and by time. Spatial sampling means the angle of view that the camera sees is broken down into the rectangular grid of pixels. Tonal sampling means the continuously varying tones of brightness in nature are broken down into individual discrete steps of tone. If there are enough samples, both spatially and tonally, we perceive it as faithful representation of the original scene. Time sampling means we make an exposure of a given duration.
The eye is a relatively sensitive detector. It can detect a single photon, but this information is not sent along to the brain because it does not exceed the minimum signal-to-noise ratio threshold of the noise filtering circuitry in the visual system. It requires several photons for a detection to be sent to the brain. A digital camera is almost as sensitive as the eye, and both are much more sensitive than film, which requires many photons for a detection.
The image deposited on film or a digital sensor is only as good as the image that emerges from the lens.Photography is all about light—light bouncing off pigments and dyes, light shining through gels and filters, and the shadows and depth that come with the absence of light. Light is one of the basic influences in life.In fact, it brings life. Without light there would be no energy on the planet except that lurking deep in its bowels. And yet we’re not exactly sure what light is. The scientific answers at times contradict each other, and if you start to peer at it too closely, the physical nature of the universe develops cracks. So we’re not going to do that, but we will look at it in less intimate terms. Pinhole cameras aside, the image deposited on film or a digital sensor is only as good as the image that emerges from the lens. The use of glass or plastic, how many pieces of plastic or glass elements make up the lens, and the precision with which its focusing and zooming mechanisms work all determine the quality and price of a camera.