Hardware and colour models

Question 1

The RGB model

Answer 1

regarded as the most
common digitally coded colour model and employs the three
primary colours of red, green, and blue
additive colour model
colours are specified on the intensity of the hues.
can be represented as a cube.

Question 2

additive colour model

Answer 2

meaning that the presented colours
are generated through combinations of the three primary colours

Question 3

Advantages of RGB model

Answer 3

relating nicely to the method of colour
production on graphic displays

Question 4

Disadvantges of RGB model

Answer 4

Common notions of hue, saturation, and lightness are not inherent in the model.
Steps in RGB color space do not correspond to equal visual steps.
An incremental change found in low RGB values typically represents a smaller visual difference than the same incremental change in high RGB values

Question 5

The CMYK model

Answer 5

consists of three secondary colours, cyan, magenta, yellow, and
black.
Subtractive primary colours
Printed maps create colour using a subtractive process they are based on reflected light.

Question 6

subtractive primary
colours

Answer 6

are formed by subtracting the primary colours from a white surface

Question 7

Disadvantage of CMYK

Answer 7

there is a lack of relation to common colour terminology, and equally spaced colours in the model will not correspond to equal visual steps

Question 8

The HSV model

Answer 8

allows users to work directly with hue, saturation, and value.
HSV colour space is represented as a hexcone based on RGB colour model, viewed in a hexagonal fashion.

Question 9

Hue

Answer 9

describe the colour and defines in a counterclockwise
angle from red

Question 10

Saturation

Answer 10

tells how much quantity of respective colour
must be added. Complete pure colour added means 100%
saturation while no colour is 0% resulting in grey scale

Question 11

Value

Answer 11

defined as the height along the central vertical axis, represent lightness concerning colour saturation. As the values
increase, hues become more saturated and brightness increases

Question 12

Munsell Models

Answer 12

using hue value and chroma (saturation), the same a sHSV except it is assymmetrical

Question 13

Advantage of Munsell Model

Answer 13

equal steps in the model represent equal perceptual steps.
A colour that is numerically midway between two other colours should appear to be perceptually midway between those colours

Question 14

HVC Model

Answer 14

Computer model of Munsell model
Both have irregularly shaped colour space.
hue is specified in degrees
counterclockwise from 0 (red)
No longer distributed model.

Question 15

CIE

Answer 15

imitates human perception of image colours.
careful colour specification in the CIE model means that anyone in the world should be able to recognize and reproduce a desired colour. Combination of three numbers is used.

• CIELUV is appropriate for graphic displays, and
• CIELAB is appropriate for printed material

Question 16

graphic display

Answer 16

describe the computer screen on which a map is displayed in soft-copy form
cathode ray tubes (CRTs), liquid crystal displays (LCDs)

Question 17

Vector

Answer 17

the hardware moves to one location and draws to the next location. Images are composed of drawn lines.

• The connected sloped lines are traced by the electron beam, which travels along a random route
• The beam skips the darkest regions of the image without stopping at their focal points

Question 18

Raster

Answer 18

The image is composed of pixels which are created by scanning from left to right and from top to bottom.
An image is subdivided into various horizontal lines, known as scan lines, which are then further divided into various pixels to help further process the image.
Raster scanning involves sweeping the electron beam across the display one row at a time from top to bottom.
The intensity of the electron beam is switched on and off as it goes over each row, resulting in a pattern of illuminated spots on the screen.
Collectively, the intensity values for each screen point, known as pixels, are stored in a memory section called refresher buffer.
Each pixel corresponds to a unique location in the image.
The refresher buffer stores an image definition of a raster scan.

Question 19

Resolution

Answer 19

the number of pixels in the frame buffer and
dictates how much detail you can see in the image

Question 20

frame buffer

Answer 20

the number of bits used per pixel.
determines properties such as how many colours can be represented on a given system
There is at least 24 bit per pixel in full-colour also known as true-colour or RGB-colour systems

Question 21

CRT

Answer 21

created by firing electrons from an electron gun at phosphors, which emit visible light when they are struck.
Monochrome only has 1 gun.
Colour have 3 guns -R,G,B.
Delta and in-line are two common arrangements of electron guns and phosphors.
A shadow mask or aperture grill (“Metal mask”) is positioned so that each electron gun can hit only one type of phosphor.
Different colours on a CRT screen result from the principle of additive colour - colour phosphors are visulaly added to create other colours.

Question 22

Advantages of CRTs

Answer 22

• affordable as compared to other monitors with comparable components
• CRTs run at the highest pixel resolutions generally available
• Produce a very dark black and the highest contrast levels normally available - suitable for use even in dimly lit or dark environments

Question 23

Disadvantages of CRTs

Answer 23

• bulky size and high energy consumption
• have a lower refresh rate than modern LCD screens, moving images will appear less smooth
• Subject to geometric distortion and screen regulation problems. Also affected by magnetic fields from other equipment including other CRTs

Question 24

LCDs

Answer 24

a complex sandwich of a light source, glass plates,
polarizing film, liquid crystals, a source of electrical power and colour filters.
The liquid crystals found at each pixel location initially are all in the same orientation.
When polarized light passes through the crystals, the crystals direct
the light so that it passes through another polarized filter, a resultant bright light is observed.
Colour is created by using red, green, and blue coloured filters.
If an electrical charge is applied to a liquid crystal, the crystal is bent and
some of the light does not pass through—the intensity of the light we see is a function of how strong a charge is applied.

Question 25

Advantages of LCDs

Answer 25

• LCDs are light weight, small depth (or small footprint)
• Absence of flicker
• Low power consumption
• Absence of potentially harmful x-rays and low-frequency magnetic fields

Question 26

Disadvantages of LCDs

Answer 26

• Smaller range of available colour, optimal performance at only one resolution.
• Difficulty of viewing from a wide angle (although this problem is disappearing).
• Degradation in performance due to changes in ambient temperature, and the greater expense of large-format displays.

Question 27

Limitations LCDs and CRTs

Answer 27

One limitation of both LCDs and CRTs is that they cannot handle large map displays (e.g., an entire USGS topographic sheet)
* The largest CRT and LCD screens generally do not exceed 21 inches diagonally
* Alternatively, pan, scroll, and zoom functions can be used to display an entire large-format map, however sometimes a map user would rather examine the entire map at once or compare a variety of maps simultaneously