2015, Autumn Visualization with 3D CG Masaki Hayashi Color theory & Digital camera

Today’s contents Color theory (break) Digital camera

2014, Autumn Visualization with 3D CG Color theory

Light Light is electromagnetic wave.

Electromagnetic Wave Wavelength X Frequency = c (speed of light) nm ～ 1km 300,000,000 meters/second (This is constant) 3x10 20 Hz ～ 30kHz n : nano nano : 10 -9

Visible light Radiation( ɤ ) X-ray Ultra-violet Visible light Infra-red Microwave Radio wave

Color Light Object Eye Wavelength Intensity Spectral energy distribution 400nm 700nm 400nm 700nm

Color matching Obvious If this perceived as 400nm 700nm 400nm 700nm this perceived as Isometric color matching When this perceived as 400nm 700nm 400nm 700nm this could also be perceived as

Photoreceptor cell Rods and Cones Rods: Brightness Red cones: Red color Green cones: Green color Blue cones:Blue color

Color matching experiment Red Green Blue Test light Matching Test field Reference field Any color can be made from 3 primary colors (R, G, B)

Law of Trichromacy "Any color can be made from 3 primary colors" Experimental result i.3 colors are arbitrary but have to be independent each other ii.2 colors cannot work iii.Color value may become negative value When the test light is too vivid color matching cannot be done Add a color to the test light to get a matching C = R + G + B C + R = G + B C = -R + G + B C R G B negative value

From the biological point of view Any color can be represented by minimum three different colors. Only two colors cannot do this. R G B Cone Rods

RGB Color System 400nm 700nm 400nm 700nm r 1, g 1, b 1 r 2, g 2, b 2 r 3, g 3, b 3 r 4, g 4, b 4 r 5, g 5, b 5 r 6, g 6, b 6 R, G, B Sum RGB color system Line spectrum Spectral energy distribution

Color matching functions Line spectrum r = g = b = nm color matching functions

Color space R B G (1.0, 1.0, 1.0) (R, G, B) White Given test color Any color can be plotted in RGB 3D space

Color triangle R B G (r, g, b) White Given test color

Chromaticity diagram R B G White 1 1 R G B Given test color (r, g) Chromaticity diagram Presented by 2 values: r, g

0 700nm 550nm 510nm 490nm 400nm Color matching functions on the chromaticity diagram 1 1 R G White

CIE XYZ color space 0 700nm 550nm 510nm 490nm 400nm 1 1 R G White Avoid negative value Any color visible to average human eye is represented within this shape

Color representation When you choose RGB colors like this You can represent the color within this triangle and You can NOT represent the color outside of the triangle Green Red Blue

RGB color spaces sRGB (Rec. 709) (TV, HDTV, Web,...) Adobe RGB (cover CMYK color printer) Rec (Super Hi-Vision)

Some points There exists the color which cannot be displayed on a monitor. (emerald green sea, pure orange, etc.) However, the most of the color is within the color space triangle. Reproduction of intermediate color rather be more important. (linearity, gamma, monitor measurement,...) It is important to establish the pipeline from camera to monitor (color management system,...)

ClothFood_Chart Xmas_Box Lagoon Lagoon 提供：インフォーツ ( 株 ) 笠井享氏 Wide color gamut

Color which is out of "sRGB" ClothFood_Chart Xmas_Box Lagoon Lagoon 提供：インフォーツ ( 株 ) 笠井享氏 Wide color gamut

Pointer’s real-world surface colors Wide color gamut Rec can cover 99% of Pointer's colors. sRGB Adobe RGB

sRGB Monitors CS270-CN (EIZO) 10,000SEK ～ Ordinary monitor, TV set 1,000SEK ～ LV K Monitor (Sharp) 1000,000SEK Adobe RGB Rec. 2020

Some points There exists the color which cannot be displayed on a monitor. (emerald green sea, pure orange, etc.) However, the most of the color is within the color space triangle. Reproduction of intermediate color is rather more important. (Linearity, gamma, monitor measurement,...) It is important to establish the pipeline from camera to monitor Color Management System

Digital camera

Spec of digital camera Resolution Bit depth Color space

Resolution 8 megapixels (=8,000,000) :iPhone 18MP :Consumer digital camera 60MP :Hasselblad Consumer: approx. 16MP to 24MP Hasselblad : 40MP to 60MP 8M: 3465x M: 4896x M: 8944x6708 Requires good lens for high-resolution

Lens Focal length Fixed or Zoom human eye sight ≒ 50mm (35mm film equivalent) Ghosting Flare

Lens Optical aberration BarrelPincushion Lens distortion

Bit depth 8-bit e.g. Compact consumer: JPEG, TIFF 12-bit, 14-bit e.g. High-end consumer: RAW 16-bit e.g. Hasselbad: RAW

Color space sRGB e.g. Compact consumer Adobe RGB e.g. Consumer digital camera ～ High-end Rec Not so many Note: Natural color representation is not so much relevant with wide color space.

RAW data RAW + JPEG or JPEG You can choose Sensor RAW Digital process JPEG Sensor RAW Digital process JPEG Compact consumer Consumer, high-end JPEG Digital process RAW PC software

RAW data With RAW data, you can adjust: Dynamic range (lightness) Color temperature (white balance) Edge enhancement Compression ratio (uncompressed image) etc. on a PC afterward.