#13 Jun 2023 Q3(b)(iv) 2 marks 1.2.4 colour depth effect

Question

Lead-in: Binary numbers can represent images. Image is 3 px wide by 4 px high; 4 colours (Red 0000, Green 0010, Blue 1000, Purple 0110).

(b)(iv) The colour depth is increased to 2 bytes. State two effects that this change can have on the image.

1 ......................................................................
2 ......................................................................

[2]

Why this question is tricky

A common misconception is that colour depth increases the resolution of the image. This would need to be an increase in the resolution (the number of pixels) as opposed to the number of bits per pixel.— J277_01_ER_Jun2023.txt lines 255-258

MS complexity 4/10: Strict exclusions — "Do not award higher resolution, image size increases, clearer image (NBOD), more detailed image (NBOD)".

Full-marks model answer

  1. The number of colours that can be represented in the image will increase, because each pixel now has 16 bits available to store a colour code (216 possible colours).
  2. The file size will increase because each pixel now requires more bits of storage.
Mark allocation (2 marks)
  • MP1: "The quality of the image can be improved" OR "The number of colours that can be represented/used will increase // BOD more colourful".
  • MP2: "The file size will increase // takes up more storage space // image has/requires/takes up more data".

Watch out for...

Colour depth is bits per pixel, not pixels per inch. Do not write "higher resolution" or "clearer image" — the MS explicitly disallows those phrases. Use "more colours" and "larger file size".