Sensors Simplified ObjecBves Cameras Sensors (and Film) where Rays - PDF document

Sensors Simplified ObjecBves • Cameras’ Sensors (and Film) where Rays of • Photographic Processes for Digital Capture Light become Pixels • The Five Simplified layers of a CCD • Two benefits of using the Camera Raw Reading: hHps://en.wikipedia.org/wiki/Charge-coupled_device Digital: ConverBng Light to Data Digital: ConverBng Light to Data • Micro lenses : Capture Light and direct it to the light sensiBve areas of the • CCD: Charge-Coupled Device, a device for sensor. converBng electrical – Added Lens layer charge, into a digital value • Hot Mirror : Simple Filtering. Lets visible light pass, but reflects lights in the • Pixels are represented by invisible part of the spectrum (depends capacitors, which convert on kind of light to capture –e.g., and store (accumulates) infrared , ultraviolet- UV camera). incoming photons as Also provides AnB-aliasing. electron charges • Color Filter: Bayer Array separate light • Willard Boyle and George into RGB. E. Smith, 1969 (Won a • Photo Diodes: Color Blind. But measure Noble Prize in Physics in intensiBes, and energy converted to 2009). electrons • Deple8on Layer : Where Electron Are collected (part of photo diodes layer) hHps://en.wikipedia.org/wiki/Charge-coupled_device Digital: ConverBng Light to Data Dual Microlens Designs Shrinks Pixel Size Sony CCD • Microlens Array : Capture Light and direct it to the light sensiBve areas of the sensor. – Added Lens layer

Bayer Filter Hot Mirror • Cuts IR light. • Bayer Filter on a • Hot filter, that Filters out sensor infrared light to miBgate • Pixel : sensors that are sensiBve to the infrareds (750nm – square of 4 color 1250), and contaminated squares. colors. • Lets only 1 color – E.g., Fires light through. • Cold Filter – Cold Mirror – 3 PaHerns one for filters IR into the pahtway each color (more common infront of Combine lens. – CombinaBon gives us the final image Convert Light to Data Convert Bayer to RGB • R = 200 • G = 170, 180 • B = 153 ? Raw input in Bayer 
 Convert Bayer to RGB Bayer Filter • R = 200 • G = AVG(170, 180)=175 • B = 153

Demosaic ½ Green • Combine Bayer Filter & Interpola8on to esBmate other colors from the incomplete sample by With this method sensor 1/4 Blue only captures Raw color Bayer Filter Mechansism data for 1/3 of the image. Use Demosaic in order 1/4 Red to esBmate the • Bayer Filter remaining 2/3 of the image. hHps://en.wikipedia.org/wiki/Demosaicing hHp://www.csee.wvu.edu/~xinl/papers/demosaicing_survey.pdf Other Filters • Foveon: stacks photodiodes to capture all light at a single locaBon. • Fujifilm Super CCD (more neighbors) à Claims more data to work with for interpolaBon hHp://www.vividlight.com/arBcles/2514.htm Camera RAW File Format • Contains minimally processed data from the sensor • Image encoded in a device-dependent colorspace • Captures radiometric characterisBcs of the scene • Viewable image from the camera's sensor data • Like a photographic negaBve – Has a wider dynamic range or color; preserves most of the informaBon of the captured image