![]() and additionally: White balance Exposure correction Tone mapping Noise suppression Sharpening. there were CRT monitors: brightness (voltage) which needed a gamma-corrected signal 1 (max) 1 (max) monitor brightness linear JPEG RGB (max) electric input signal (max) linear brightness (Raw) Also convenient for compressing into range 10/24 Axel Mellinger (Physics, CMU) Time Lapse Astro Image Processing June 10, / 24ġ2 Raw to JPEG Conversion To-do list De-mosaicing Gamma correction. Axel Mellinger (Physics, CMU) Time Lapse Astro Image Processing June 10, / 24 9/24ġ1 Gamma Correction From Raw to JPEG A long time ago. ![]() Free/open-source software: dcraw, RawTherapee, DarkTable. Gunturk et al., IEEE Signal Processing Magazine 44, Jan Problem areas: edges, repeated patterns Camera manufacturers use their own, proprietary algorithms Commercial software: Adobe Lightroom, Photoshop. Axel Mellinger (Physics, CMU) Time Lapse Astro Image Processing June 10, / 24 7/24Ħ Photograph Through a Bayer Filter Original image Image credit: Anita Martinz / Wikipedia 8/24 Axel Mellinger (Physics, CMU) Time Lapse Astro Image Processing June 10, / 24ħ Photograph Through a Bayer Filter Recorded by sensor Image credit: Anita Martinz / Wikipedia Axel Mellinger (Physics, CMU) Time Lapse Astro Image Processing June 10, / 24 8/24Ĩ Photograph Through a Bayer Filter Recorded by sensor (color coded for clarity) Image credit: Anita Martinz / Wikipedia Axel Mellinger (Physics, CMU) Time Lapse Astro Image Processing June 10, / 24 8/24ĩ Photograph Through a Bayer Filter Recorded by sensor (this is what gets stored in a Raw file!) Image credit: Anita Martinz / Wikipedia 8/24 Axel Mellinger (Physics, CMU) Time Lapse Astro Image Processing June 10, / 24ġ0 Demosaicing = De-Bayering Many algorithms See, e.g. ![]() Camera sensors are black and white only! For color images: Take 3 separate images through red, green and blue filters or Take single image through Bayer filter pattern Source: Wikipedia Twice as many green elements as red or blue to mimic the physiology of the human eye. Axel Mellinger (Physics, CMU) Time Lapse Astro Image Processing June 10, / 24 5/24ĥ How Color is Recorded Bayer Filter Named after its inventor, Bryce Bayer of Eastman Kodak. throws away image information) Reasonably small file sizes Example: Canon T2i (18 Megapixels): MB (depending on quality settings) each color (red, green, blue) is represented by an 8-bit number 2 8 = } 2 2 = 16,384 numbers 14 factors linear image format (doubling the light intensity doubling of the brightness value) But wait, there is more. JPEG JPEG (or JPG): A lossy compression format Nearly universal format for digital cameras Uses lossy compression (i. JPEG 2 How Color is Recorded: Bayer Filter and Gamma 3 Recording Twilight Time-Lapse Videos 4 RawTherapee Demo 5 Exposure Value Smoothing and Video Processing Axel Mellinger (Physics, CMU) Time Lapse Astro Image Processing June 10, / 24 2/24ģ Introduction: RAW vs. 1 Processing Time Lapse Astro Images with RawTherapee Axel Mellinger Department of Physics Central Michigan University & Sunset Astronomical Society JAxel Mellinger (Physics, CMU) Time Lapse Astro Image Processing June 10, / 24 1/24Ģ Outline 1 Introduction: RAW vs.
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