The effect of colour depth and resolution on:quality of the image, size of an image file

Images: The effect of colour depth and resolution on:quality of the image, size of an image file

1.2.4c Data Storage: Images

Data Storage: Images — Note 4 of 4

What you need to know

Colour depth and resolution are the two main factors that affect both the quality and file size of an image. Increasing either one improves quality but increases the file size.

What to know

Increasing resolution = more pixels = higher quality (more detail) AND larger file size.
Increasing colour depth = more bits per pixel = wider range of colours = higher quality AND larger file size.
Image file size = colour depth x width (px) x height (px).

Exam technique

Tip:When asked about the EFFECT of increasing resolution or colour depth, always mention BOTH quality AND file size — they both increase.
Mistake:Only discussing quality or only discussing file size. Examiners expect you to address both.
Mistake:Saying higher colour depth gives 'higher resolution'. Colour depth and resolution are DIFFERENT things. Colour depth = bits per pixel. Resolution = number of pixels.
Tip:Maximum colours = 2^(colour depth). 4-bit = 16 colours, NOT 4. A common exam error is giving 4 colours for 4-bit depth.

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