Physics of Digital Photography:


- The most important part of a camera is, arguably, its sensor and lens. These two systems are imperative when capturing and saving an image.

- Sensor:
- The digital camera sensor is made up of millions of 'photosites' which are light capturing devices used to measure and record all incoming light every time you press the shutter button.
- Each time the shutter is raised, even if it's only for a millisecond, the photosites will be uncovered and begin to collect light photons until the shutter is shut.
- The quantity of the photons in each photosite determines the intensity of the light and how bright your image will be. You can adjust how long your shutter is open for to obtain different levels of brightness depending on the light available.

Example of different sensor sizes
 Example of different sensor sizes in digital cameras. The bigger sensors produced better quality images. Image by: https://akiwiretrospective.files.wordpress.com/2014/06/sensor-chart.jpg


- Also, to get a color image there is a color filter placed over the sensor called a "Bayer Array." This is basically a chess board looking array of alternating red, green, and blue filters over the photosites.
- Each of the different colored filters will capture a different spectrum of light and when all of the spectrum's are put together, you get a fully colored image. There are twice as many green filters as there are red and blue, this is because the human eye is more sensitive to green than any other color.

Color Filters over the photosites on a camera sensor How your Camera sees and imge vs how you see it
Different colored filters sit over the photosites on a digital cameras sensor to capture color images. Image by: https://upload.wikimedia.org/wikipedia/commons/thumb/3/37/Bayer_pattern_on_sensor.svg/350px-Bayer_pattern_on_sensor.svg.png
 How you see an image vs how your camera sees it. Image by cambridgeincolour.com


- The bigger the sensor on your camera, the more sensitive to light your camera will be. Cameras with bigger sensors tend to cost more because they produce better results in lower light.

- After snapping the image and storing the light intensity into the photosites, the entire file is converted into an array of numbers which represent the intensity and location of each photosite so the image can be stored onto your digital storage for later reconstruction on a computer.

- Lens
- Lenses have always been an integral part of cameras, no matter how old. Without a lens, your camera would not have anything to 'guide' the light to the sensor or to focus on what you want to make an image of.
- A camera lens basically uses physics by being designed in a way to 'bend, refract, and focus' light so we can make the image we are looking for.
- Lenses are relatively simple in that they refract light and direct it towards the back of your camera, where the sensor is.
    - As light hits the front element of a lens, it starts to slow down and is directed to a certain angle. The lens is designed so that the light will always be directed at the same angle, no matter how it comes into the lens. The bending angle is the same throughout the lens, but it may differ for different lenses.

Example of how a camera lens bends the light towards the sensor
 Example of how a camera lens 'bends' and refracts light towards its sensor. Image by: http://www.rags-int-inc.com/phototechstuff/lens101/LensDiagram_1024.gif


    - This angle is important when focusing the beams. Light bending at different angle will converge at different points depending on how they enter the lens. The beams are all directed at the same angle, but they don't always converge at the same point. This affects your focus. Lenses compensate for this by having a focusing ring which will turn and essentially move the lens closer or further from your sensor until the light converges at the right spot making your image in focus.

Demostration on how distance affecs focusing
 The subject is only in focus at one point, where the light converges after being refracted by the lens. The lens compensates for this by allowing you to move the lens closer and further to the camera sensor, allowing to achieve the desired focus. Image by: http://electronics.howstuffworks.com/camera1.htm

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