Which is the Pink Pen?

Here is the Pink Pen

(Example taken from http://www.colourblindawareness.org)

Light and Colour

The Solar Cell

Converts light into electricityThe stronger the light the more electricity

Measure the Current to Measure the Light Levels

Voltage

Light

Analogue to Digital Conversion

To store three volts we need 2 bits00 = 001 = 110 = 211 = 3

0 3

Light

Analogue v Digital Data

How to represent 10 hours and 15.34567890 minutes?

Quantisation Error

White 15% Grey 30% Grey0 0.3 0.4

White White White0 0 0

Our analogue source gives us

The digital representation becomes

When Applied to an Image

Create an Array of Digital Detectors

Project the Image onto the Array

Using 1 bit per Pixel

Increase the Image Resolution

Increase the Colour Resolution

Colour Resolution and Image ResolutionColour Resolution relates to the depth of

colour the image reproduces. The more bits we use to represent a single pixel the greater the number of colours may be stored in that pixelColour resolution is not related to the size of the

imageWe could have a 1 x 1 pixel image and still have a

colour resolution of 16 million colours – 24 bit colour! (Not that there would be a lot of point.)

 Image resolution relates to how many pixels make

up the height and width of the image per inch – dots per inch. Image resolution is an issue when it comes to the

size of the image in dpi

Low Image Resolution Images Don’t Re-Size Well

Both images have high colour resolution

Colour Representation - RGB

Combine Red Green and BlueAlso referred to as 24 bit colourVery common in computing

Black rgb(0,0,0)Red rgb(255,0,0)Green rgb(0,255,0)Blue rgb(0,0,255)Yellow rgb(255,255,0)Cyan rgb(0,255,255)Magenta rgb(255,0,255)Grey rgb(192,192,192)White rgb(255,255,255)

CMYK (Cyan, Magenta, Yellow & Black)

Subtract RGB by mixing Cyan Magenta Yellow and BlackCommon in printing industry and computer printers

The Scanner

InterpolationHow can a 600dpi scanner scan at 1200 dpi?

Without Interpolation With Interpolation

Digital to Analogue ConversionThe Display Adapter / Monitor – Device Resolution

In the case of a monitor, the quality of the equipment is called the dot pitch.

The dot pitch is the distance in millimetres of dots of the same colour.

In the case of a typical monitor the dot pitch is .28, meaning there is .28 mm between the red dots (green dots or blue dots). 

The smaller the dot pitch, the higher the quality of the equipment.

The Output from the Graphics CardImagine we scanned in an A4 document at a

resolution of 600 dpi.Displayed on a monitor with a 72dpi graphics

adaptor

Very Common in Student Work

More important when we design for mobile devicesDesign for liquid layout

Displays with Lower Colour ResolutionQ. “How do I view a 16 million colour image

256 colour display?”A. Dithering

A is the original unchanged image B is 1 bit monochrome with dithering C is 1 bit monochrome without dithering

– note the loss of detail D is 8 bit colour with dithering

– note the speckled effect which is common to this process

Gamma CorrectionImages do not display the same across

different hardware platforms

Becomes