Digital Images and Pixels

Question 1

What are pixels made up of?

Answer 1

• 3 dots - RGB.

- They are rectangular mosaic and all the same size and uniform.

Question 2

How many pixels in one mega pixel?

Answer 2

• 1 million.

Question 3

The more pixels the more …?

Answer 3

• Detail.

- Scene it can capture.

Question 4

What do grey levels do?

Answer 4

• Tell a computer how bright to make each pixel.

- Binary information.

Question 5

What is a bit?

Answer 5

• A single unit of information and this information is a physical thing.

Question 6

What is the function of a bit?

Answer 6

• To store a value.

Question 7

What is a single bit the result of?

Answer 7

• A single decision.
• Either 0 or 1 / Yes or No / On or Off.
• Stores the answer to a question.

Question 8

How are Bits read?

Answer 8

• As numerical values.

Question 9

What is a byte?

Answer 9

• A combination of 8 bits.

Question 10

What are “capture devices” capable of?

Answer 10

• How much colour is presented in any 1 given location.

Question 11

How many different levels of colour can be assigned to each pixel location?

Answer 11

• 256 different levels of colour can be assigned to each pixel location.

Question 12

What do the 3 colour channels provide?

Answer 12

• Full colour spectrum.

Question 13

What is each pixel assigned?

Answer 13

• 1 of the 256 different colour levels from each colour channel.

Question 14

Why are 256 different colour levels sufficient?

Answer 14

• Sufficient to create a smooth transition from light to dark.
• 8 bits per channel is compatible with the majority of input and output devices.

Question 15

What is bit depth?

Answer 15

• The number of bits describing and recording tonal and colour variation.

Question 16

What occurs if we increase the number of bits?

Answer 16

• The more shades of grey we get.

Question 17

What does the number of bytes and file size depend on?

Answer 17

• The number of pixels.
• The number of bits.
• Image compression.

Question 18

What is a fake image?

Answer 18

1. An image not created by a camera.

2. Image originating from a camera but altered to change the meaning.

Question 19

How can we identify fake images?

Answer 19

• Breaks the laws of physics.
• Differences in images themselves.
• Image lighting and shadows.
• Relationship between neighbouring pixels.

Question 20

Why is it difficult to make a fake image look real?

Answer 20

• A computer can’t always determine the grey levels.
• Antialiasing - edges of pixels adopt transitional colours.
• Displaying small - not detected with the naked eye.

Question 21

What is a colour channel?

Answer 21

• A mode where image information is stored.

- Present in programs such as PS.

Question 22

What is a capture device?

Answer 22

• Measures the amount of colour in 1 location.

Question 23

What are 8 bits sufficient for?

Answer 23

• A good quality image.

Question 24

What does a higher bit depth result in?

Answer 24

• Greater potential for colour accuracy.

Question 25

Give 5 image file formats.

Answer 25

1. RAW. 2. JPEG - point photographic experts group. 3. TIFF - tagged image file format. 4. PS document. 5. GIF - a lossless format for image files that supports both animated and static images.

Question 26

What is 1 byte?

Answer 26

8 bits.

Question 27

What is 1 KB?

Answer 27

1024 bytes.

Question 28

What is one MB?

Answer 28

1024 KB.

Question 29

What is one GB?

Answer 29

1024 MB.

Question 30

What is a RAW image?

Answer 30

- An image with more than 8 bits per channel. - Useful for extensive tonal / colour correction. - Is more mouldable than JPEG. - A raw file is the image as seen by the camera's sensor. - - Think of it like unprocessed film. Rather than letting the camera process the image for you, turning it into a JPEG image, shooting in raw allows you to process the image to your liking.

Question 31

What is a colour gamut?

Answer 31

- Range of colours within spectrum available to a particular device.

Question 32

What is a colour gamut dependant on?

Answer 32

- Paper quality. - Colourant used. - Gamut of document.

Question 33

What is resolution?

Answer 33

- Specifies size of a pixel (a dot of coloured light on monitor).

Question 34

What 2 resolutions are often in play in a document?

Answer 34

- Digital file resolution. | - Output device resolution.

Question 35

What is overall resolution dependant on?

Answer 35

- Capture size. - Image resolution. - Monitor resolution. - Printer resolution.

Question 36

What is meant by dpi and ppi?

Answer 36

Dpi - dots per inch. | Ppi - pixels per inch.

Question 37

Why might we rescale an image?

Answer 37

- For the intended output. | - Before retouching and enhancing.

Question 38

What is meant by constrain proportions?

Answer 38

- The height and width of a document is linked.

Question 39

What is meant by resampling?

Answer 39

- File size increases or decreases to accommodate changes. - Pixels are added. - This does not affect the pixel dimensions.

Question 40

What is meant by downsampling?

Answer 40

- Decreasing the number of pixels.