Light and Digital Sensors

Light and Digital Sensors

The traditionalist

Anyone who has ever owned a traditional camera understands that light has an effect on the surface of the camera’s film.

When the shutter opens, it allows light to enter the camera. The lens reflects the image directly onto the film.

The reflected image tells the film how to record the light that came through the open shutter.

All of this is affected by the camera’s settings, including the film speed (ISO), aperture (F-stop) and shutter speed as well.

Digital

Digital photography has a great deal of the same language and also requires the use of the shutter, ISO and f-stop, as well as a special medium that is capable of recording the image in front of the camera accurately.

The digital age means that no film stock is placed into the body of the camera, and instead a sensor receives and interprets the data.

The same effects are created by the camera settings, with the exception of the interpretation of true colors, and only the recording of the image takes place in a different manner.

Currently there are two available devices that are installed within the bodies of digital cameras as a means of recording images – CCD and CMOS – both of which are referred to as sensor.

The CCD means “charge-coupled device” and CMOS translates to “complementary metal oxide semiconductor” and both result in the same process within the camera’s sensor unit.

What is a sensor?

Basically the sensor device is covered by a grid of miniscule electrodes known as “photo sites”. Every single digital photograph is composed of the data translated by photo sites, usually called pixels.

Path of light through a digital SLR camera

Before the camera allows the shutter to open it charges all of the photo sites in the sensor. When light strikes them they release some of their electrons and the software within the camera then measures each of the areas of the grid to record the locations of all of the electrons.

These are then converted through a special converter which ultimately translates to pixels and the photographic image that is stored on the camera’s memory card.

Additionally, the sensor and photo sites must be able to record or understand colours which is accomplished by a filter applied to the surface of the sensor, and which is capable of distinguishing a set range of colours within the recorded image.

Eliminating the mystery

Understanding how the sensor of a digital camera works is not as important as understanding the effects achieved through changing the settings, but it does help to eliminate any of the mystery around taking photographs in this popular and rapidly advancing format.

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