Effect of resolution and colour depth on image quality and file size

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Quick Questions

Shade in the A or B circle for each question.

1. A student increases the resolution of an image from 400 x 300 to 1600 x 1200 pixels. What happens?

A The image has more pixels, so it shows sharper detail and the file gets larger

B The image has more pixels, so it shows sharper detail and the file gets smaller

2. Which image is most likely to look pixelated (blocky) when enlarged?

A A low-resolution image with few pixels

B A high-resolution image with many pixels

3. An image uses a very low colour depth, and the sky shows visible stripes of colour instead of a smooth blend. What is this effect called?

A Sampling

B Banding

4. What is the effect of increasing the colour depth from 8 bits to 24 bits per pixel?

A Smoother colours, but a larger file

B Smoother colours, and a smaller file

5. Which statement about image quality and file size is correct?

A Higher quality usually means a smaller file size

B Higher quality usually means a larger file size

Match the Pairs

Draw a line connecting each item on the left to its match on the right.

Left column		Right column
1resolution: 640x480 -> 1920x1080		AMore bits per pixel, so colours look smoother but the file is larger
2colour depth: 4 bits -> 24 bits		BMore pixels in the image, so it shows sharper detail but the file is larger
3A low-resolution image has too few pixels, so it looks blocky and pixelated when enlarged		Ccolour depth = 2 bits -> banding, small file
4A low colour depth has too few colours, so smooth gradients show visible bands of colour (banding)		DIncreasing colour depth gives smoother colours and uses more bits per pixel, so the file gets larger, not smaller.
5Higher resolution = fewer pixels = sharper image		EHigher resolution means MORE pixels, not fewer. More pixels give sharper detail but also a larger file.
6Increase colour depth -> same quality, smaller file		Fresolution = 32x32 -> pixelated, small file

Definitions

higher resolution and colour depth

Fill in the Blanks

Complete each line of code by filling in the missing parts.

IF resolution _ oldResolution THEN OUTPUT "Sharper detail, bigger file" ENDIF

IF colourDepth > oldDepth THEN fileSize ← fileSize _ extraBits ENDIF

IF colourDepth _ 4 THEN OUTPUT "Banding appears" ENDIF

IF lowResolution = ____ THEN OUTPUT "Pixelated image" ENDIF

IF highResolution ___ highDepth THEN OUTPUT "Sharp, smooth, larger file" ENDIF

Spot the Error

Shade in the letter of the line that contains an error.

Question 1

A image = 'photo'

B resolution = 'low'

C look = 'sharp'

D print(image, look)

Question 2

A depth = 'low'

B colours = 'few'

C sky = 'has banding'

D file_size = 'large'

Question 3

A pixels = 'many'

B detail = 'sharp'

C print('Sharper and smaller')

Question 4

A depth = 'high'

B gradients = 'banded'

C file_size = 'larger'

Question 5

A if resolution = 'high':

B detail = 'sharp'

C else:

D detail = 'pixelated'

Answer Key

Effect of resolution and colour depth on image quality and file size

Section A: Quick Questions

A — The image has more pixels, so it shows sharper detail and the file gets larger

A — A low-resolution image with few pixels

B — Banding

A — Smoother colours, but a larger file

B — Higher quality usually means a larger file size

Section B: Match the Pairs

resolution: 640x480 -> 1920x1080 → More pixels in the image, so it shows sharper detail but the file is larger

colour depth: 4 bits -> 24 bits → More bits per pixel, so colours look smoother but the file is larger

A low-resolution image has too few pixels, so it looks blocky and pixelated when enlarged → resolution = 32x32 -> pixelated, small file

A low colour depth has too few colours, so smooth gradients show visible bands of colour (banding) → colour depth = 2 bits -> banding, small file

Higher resolution = fewer pixels = sharper image → Higher resolution means MORE pixels, not fewer. More pixels give sharper detail but also a larger file.

Increase colour depth -> same quality, smaller file → Increasing colour depth gives smoother colours and uses more bits per pixel, so the file gets larger, not smaller.

Section C: Definitions

higher resolution and colour depth — Raising either one improves image quality (sharper detail, smoother colours) but stores more bits, so the file size gets larger.

Section D: Fill in the Blanks

IF resolution > oldResolution THEN
  OUTPUT "Sharper detail, bigger file"
ENDIF

IF colourDepth > oldDepth THEN
  fileSize ← fileSize + extraBits
ENDIF

IF colourDepth < 4 THEN
  OUTPUT "Banding appears"
ENDIF

IF lowResolution = TRUE THEN
  OUTPUT "Pixelated image"
ENDIF

IF highResolution AND highDepth THEN
  OUTPUT "Sharp, smooth, larger file"
ENDIF

Section E: Spot the Error

C — A low-resolution image has few pixels, so it looks pixelated and blocky, not sharp. Line 3 should be look = 'pixelated'.

D — A low colour depth uses fewer bits per pixel, so the file is small, not large. Line 4 should be file_size = 'small'.

C — More pixels give sharper detail but store more bits, so the file gets bigger, not smaller. Line 3 should say the file is bigger.

B — A high colour depth has more possible colours, so gradients look smooth. Banding happens with a low colour depth. Line 2 should be gradients = 'smooth'.

A — A single = assigns a value. To compare in an if statement you need ==. Line 1 should be if resolution == 'high':.