What happens inside a Digital Camera
The processes inside a digital camera can be grouped sequentially – before, during and after the exposure:
Before exposure the digital camera shows a preview of the image either on the camera monitor or a viewfinder.
Additionally three basic things happen as already during decades before photography became digital:
- Focusing = setting the lens to a distance that will get best possible sharpness – the task of autofocus
- Exposure metering and exposure control determine the exposure.
- A camera automatic or you decide about flash mode – if the picture will be taken with flash, when the flash will be fired – the flash synchronization – and how bright the flash will light up. The latter can be adjusted with a flash compensation.
During exposure light passes through the lens and to the image sensor.
On this way image defects occur, e.g. distortions that make a straight line slightly bended.
The photo is captured by the exposure, i.e.
- for the duration of the exposure time
- light falls through an opening in the lens – the aperture – onto the image sensor
- and is amplified depending on its required sensitivity to light – the ISO sensitivity.
Nowadays it is common that cameras apply some kind of technical tricks to compensate camera vibrations during the exposure time to reduce picture blurs.
After the exposure the image sensor delivers raw data of the image.
Depending on your camera and its settings you may get this data as a file on its own or not. If so, this RAW file needs additional processing and specialized software to view it.
Additionally the camera internal image processing can create a file for viewing with any common program – usually in JPG format.
The steps to get it are:
- Bayer interpolation – a rather technical step that combines the three basic colors red, green and blue which are captured at slightly different locations next to each other into pixels with all three color components
- white balance = correction of color rendition
- image optimization = fine tuning of contrast, color saturation, sharpening, brightness and noise reduction
- Depending on your camera model additional image processing may happen for additional improvement, special effects or marketing gimmicks.
- Finally the image data has to be converted into a JPG file. Doing so the level of data compression has to be defined and the image size may be reduced.