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Fundamentals Of Imaging > Short Answer Questions > Flashcards

Short Answer Questions Flashcards

1
Q

What are the features of a GIF file format?

A

Smaller file size
8 bits per channel
Block graphics not photographs

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2
Q

What is the principle of JPEG compression?

A

Lossy compression
Most commonly used file type
Physically removes pixels
Doesn’t preserve layers
Very small file size
Works well for big complex pictures that use a lot of gradients
Not ideal for images with solid lines or text

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3
Q

What colour conversion does JPEG carry out?

A

RGB to YCrCB

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4
Q

What does YCrCB stand for?

A

Luminance, Chroma; Blue; Chroma; Red

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5
Q

What does JPEG stand for?

A

Joint Photographic Expert Group

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6
Q

What are the positives of JPEG?

A

Portable
Compatible with almost every imaging application and ah hardware devices
High resolution and fast moving images = no blur
Used on a camera
Suitable for over internet transfer
Down to 5% of original file size

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7
Q

What are the negatives of JPEG?

A

Lossy compression
Quality reduction
Doesn’t support layered images
High resolution cameras support higher resolution

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8
Q

What are the advantages of describing colour using language?

A

Universally understandable
Portrayal of emotions
Creative variation
Colour space based on the human visual system
Symbolic uses
20-100 colour description terms can cover most possible needs

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9
Q

What are the disadvantages of describing colour using language?

A

Not numerical
Subjective
Colour blindness
Difficult to replicate colour spaces reliant on binary
Emotion = difficult to portray numerically
Population dependant
Different meanings across different cultures

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10
Q

What are 2 colour ordering systems based on human perception?

A

CIELAB + Munsell Colouring System

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11
Q

Describe CIELAB

A

Colour space by CIE (International Commission of Illumination)
Expresses colour in 3 numerical values
L* = lightness
a= green-red
b= blue-yellow
3D colour space
Integer space with digital representation
Colour differences that you perceive correspond to distance when measured colour metrically

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12
Q

What does each axis represent in CIELAB?

A

Vertical Axis - extends from 0 (Dark) up to 100 (Light)
Diagonal from Left down to right -a* = green +a* = red
Diagonal from Left up to right -b* = blue +b* = yellow

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13
Q

What is the Munsell colour system?

A 
Colour space based on 3 properties 
1. Hue
2. Value (lightness)
3. Chroma (colour purity)
Differences from grey at given hue, lightness.
Based on perceived "equidistance"
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14
Q

Describe the Munsell colour system?

A
  1. Constructed around a circle with 10 segments arranging colours at equal distance
  2. Opposing pairs result in achromatic mixture
  3. Irregular cylinder with value axis (light/dark) running up and down through it
  4. Dark colours at the bottom and light at the top measuring 1 (dark) to 10 (light)
  5. Horizontal slice of cylinder across axis in a hue circle divided into 5 principles.
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15
Q

What 5 principles is the hue circle in the Munsell colour system divided into?

A
  1. yellow
  2. red
  3. green
  4. blue
  5. purple
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16
Q

What intermediates are the 5 principles in the hue circle in the Munsell colour system divided into?

A
  1. yellow-red
  2. green-yellow
  3. blue-green
  4. purple-blue
  5. red-purple
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17
Q

How is colour specified in the Munsell colour system?

A
  • Specified by selecting one of these 10 hues - referring to the angle inside them fro 0-10.
  • Chroma measured out by centre of the wheel w/ lower chroma = less saturated
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18
Q

Why are CMY primaries used in colour printing?

A
  • Subtractive colour mixing.
  • CMY colours are often in the form of pigments and inks.
  • More colour range.
  • More vibrant.
  • Important for creating sharper text.
  • Better shadow detail.
  • RGB can sometimes give an image a pink hue.
  • Covers most colour ranges quite easily - compared to using RGB.
19
Q

Provide two economic reasons why K is often used in conjunction with CMYK inks.

A
  • Cheaper than combining all 3 inks to create black.

- Printer won’t be working as hard - uses less energy and won’t need to be serviced or re-profiled as often.

20
Q

How does a bi-level printer work?

A

Process called “dithering” to distribute dots of black and white ink in a pattern varied to simulate different shades of grey.

on/off dot can only be black or white

21
Q

What 4 factors influence the colour gamut of an inkjet printer?

A
  1. Paper type 2. Ink levels 3. Gamut of document 4. Rendering intent used
22
Q

Why is the quality of an image taken on an SLR camera better than one taken with a compact camera?

A
  • Bigger and better sensor - pixels on a compact camera suffer from interference (noise).
  • Can export in RAW format (more bits per channel).
  • RAW format allows greater level of detail and allows more flexibility when editing photos earlier on.
  • Good for a sequence of moving photos.
  • Focuses on the subject more quickly.
  • Manually controlled.
  • Autofocus settings.
23
Q

What does SLR stand for?

A

Single Lens Reflex.

24
Q

Describe what is meant by the terms “device dependant” colour space.

A
  • The way in which a device renders information is entirely dependant on the device itself.
  • E.g. RGB colours (a device dependant colour space) can be different across different displays or output devices.
  • Resultant colours depend on equipment or set up used to process it.
  • Will alter if you change the display of your computer for e.g.
25
Q

What is meant by “device independent” colour space?

A
  • Colour space where colour fidelity and quality will be consistent from one device to another - so independent to any device.
26
Q

What is a device independent colour space useful for?

A
  • Producing accurate copies and colour matches
  • Industry standard
  • Transfer across a wider range of devices
27
Q

Give examples of device independent and dependant colour spaces.

A

Independent: CIELAB
Dependant: RGB

28
Q

What advancements have been made in modern digital cameras have been made since the 1975 Kodak prototype?

A
  • Developments of wireless cameras.
  • Kodak “Easy Share camera” 2001 - easy to snap pictures then download to a computer.
  • 2000: Sharp JSH04 - first digital camera in mobile phone = more portable and accessible to the public.
  • 2007: iPhone Camera - shot in different lighting conditions easily.
  • Improvements in memory technology.
  • Better zoom.
  • The Casio QV-10, released in 1995, was the first camera to incorporate an LCD screen on the back that would preview images for the user.
29
Q

How does the Bayer filter work?

A
  • The Bayer Filter splits the amount of mega pixels available on their sensor into green, red and blue.
  • Interprets this information into the information missing from the image.
  • Only have some information for each of the pixels - so essentially averages the information from either side.
  • Exploits the fact we don’t see colour that well - good luminance makes up for poor colour quality.
30
Q

What is the Bayer filter?

A
  • A CFA (a colour filter array) that tells the camera how much light has hit a certain position.
  • Arranged in a grid format.
  • Each position represents a pixel in our image.
  • A physical set of elements that intercept certain wave lengths.
31
Q

Why are there more green elements than red or blue?

A
  • We distinguish luminance much more in the green channel, so more green will look sharper to us - good luminance makes up for poor colour quality.
32
Q

What is demosaicing?

A
  • Used to determine complete values of green blue and red from a CFA.
  • Converts the mosaic into an equally sized mosaic of true colours.
  • Each coloured pixel can be used more than once.
  • Averaging the values from the closest surrounding pixels.
33
Q

What is meant by lossy compression?

A
  • Reduces image size by removing parts of the image - can reduce up to 4% of original size.
  • Enables greater space saving at the price of losing image detail.
  • Redundant information is removed.
  • Take advantage of known limitations to the human visual system.
34
Q

What two statistical properties of image compression might be exploited to reduce data storage?

A
  • Resolution.
  • File size.
  • Pixels.
35
Q

What are the differences in acuity in cone and rod cells?

A
  • Cone: High spatial acuity.

- Rod: Low spatial acuity.

36
Q

What is meant by spatial acuity?

A

The ability to discriminate fine details of the visual scene.

or

Detection of the shape of a test object. E.g. noticing subtle differences in similar shapes.

37
Q

Where are colour matches determined?

A

at CONE level.

38
Q

How are colours matched?

A
  • People can match any colour using a test stimulus by adjusting the intensity of 3 superimposed light sources generating 3 different lights.
  • Match cone response = matching colour.
39
Q

Provide 2 adaptations of the human visual system in response to the lighting present in the scene.

A
  1. Iris: sphincter muscle which allows it to expand or contract - pupils get larger or smaller control amount of light able to enter.
  2. Retina: contains light sensitive cells that can determine light, dark, colour to assemble images of the world.
40
Q

What is meant by simultaneous contrast?

A

When 2 colours are side by side interact with each other and change our perception accordingly.

41
Q

Apart from copyright describe 2 other types of intellectual property and suggest an example for each.

A
  1. Trade mark - symbol used for brands. Word or words legally registered or established by the use of representing a company or product. Can be a sign that identifies you as the owner of your goods or services. E.g. NSB, IBM. E.g. brand names: Apple.
  2. Patents - used for an invention - protect the function and processes of an object.
42
Q

What 3 things must an object have in order to qualify for a patent?

A
  1. NEW.
  2. Made or used.
  3. Inventive - not just a simple modification.
43
Q

Explain what is meant by copyright and can it be applied to an idea?

A
  • Applies to: music, art, layout, literature, drama.
  • Something that can be bought or sold.
  • Automatic right.
  • Prevents people from knowingly and deliberately copying your work.
  • Belongs to the creator.
  • Form of intellectual property.
  • Ideas cannot be copyrighted - has to be expressed in a material form.

Fundamentals Of Imaging (10 decks)

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