{[ promptMessage ]}

Bookmark it

{[ promptMessage ]}

lecture7 - CSE472 Computer Graphics Light and Color Light 1...

Info icon This preview shows pages 1–12. Sign up to view the full content.

View Full Document Right Arrow Icon
1 CSE472 Computer Graphics Light and Color Light…
Image of page 1

Info icon This preview has intentionally blurred sections. Sign up to view the full version.

View Full Document Right Arrow Icon
2 CSE472 Computer Graphics Achromatic Light Achromatic light   light represented by shades of a single color.   A B&W TV is an achromatic device.  Light is described with a single parameter Intensity or luminance  (physical properties) Brightness (perceived) 
Image of page 2
3 CSE472 Computer Graphics Monitors (CRT’s) Cathode Ray Tubes - Phosphor Attractor Grid + Control Voltage Deflection Magnets Electron Beam Control Grid
Image of page 3

Info icon This preview has intentionally blurred sections. Sign up to view the full version.

View Full Document Right Arrow Icon
4 CSE472 Computer Graphics Monitors (LCD’s) Polarizer Polarizer Liquid Crystal Backlight Viewer
Image of page 4
5 CSE472 Computer Graphics Gamma A CRT electron gun does not have a linear  relationship between voltage and intensity.  The   relationship is: k -  constant of total intensity N - number of electrons falling upon the phosphor.   I - intensity.   The value  γ  is a parameter of the CRT and varies in  the range 2.2-2.5 for most CRT’s.  This is called  gamma   LCD’s have a similar property I = kN γ
Image of page 5

Info icon This preview has intentionally blurred sections. Sign up to view the full version.

View Full Document Right Arrow Icon
6 CSE472 Computer Graphics Gamma Correction If gamma is not corrected for, a non-linearity  will appear in the output.   Gamma Correction K and  γ  are functions of the monitor design.   Real systems do this (c in range [0,1]): V = (I / K) 1/ γ γ / 1 * 255 c I =
Image of page 6
7 CSE472 Computer Graphics Gamma Correction Curves 0 0.2 0.4 0.6 0.8 1 1.2 0 0.2 0.4 0.6 0.8 1 1.2 Gamma 1.3 Gamma 2.2
Image of page 7

Info icon This preview has intentionally blurred sections. Sign up to view the full version.

View Full Document Right Arrow Icon
8 CSE472 Computer Graphics Gamma Correction Values Monitors typically range from 2.2-2.5 Correction values are often more like 1.3 Why? Where should gamma correction be done? When do we need it?
Image of page 8
9 CSE472 Computer Graphics Intensity Levels Graphics systems are typically discrete Fixed number of intensity steps How many do we need? Dynamic range Ratio between largest and smallest value If min=light of one candle and max=light of the sun, even 65536 steps will be very perceptible
Image of page 9

Info icon This preview has intentionally blurred sections. Sign up to view the full version.

View Full Document Right Arrow Icon
10 CSE472 Computer Graphics Common Bit Sizes Used Computer graphics 8 bits = 256 steps You can see the steps Commercial television 10 bits = 1024 steps Motion pictures 10-12 bits = 1024-4096 steps Generally imperceptible
Image of page 10
11 CSE472 Computer Graphics Chromatic Light Color Perception Hue  - Hue distinguishes colors in the spectrum. 
Image of page 11

Info icon This preview has intentionally blurred sections. Sign up to view the full version.

View Full Document Right Arrow Icon
Image of page 12
This is the end of the preview. Sign up to access the rest of the document.

{[ snackBarMessage ]}

What students are saying

  • Left Quote Icon

    As a current student on this bumpy collegiate pathway, I stumbled upon Course Hero, where I can find study resources for nearly all my courses, get online help from tutors 24/7, and even share my old projects, papers, and lecture notes with other students.

    Student Picture

    Kiran Temple University Fox School of Business ‘17, Course Hero Intern

  • Left Quote Icon

    I cannot even describe how much Course Hero helped me this summer. It’s truly become something I can always rely on and help me. In the end, I was not only able to survive summer classes, but I was able to thrive thanks to Course Hero.

    Student Picture

    Dana University of Pennsylvania ‘17, Course Hero Intern

  • Left Quote Icon

    The ability to access any university’s resources through Course Hero proved invaluable in my case. I was behind on Tulane coursework and actually used UCLA’s materials to help me move forward and get everything together on time.

    Student Picture

    Jill Tulane University ‘16, Course Hero Intern