Two versions of the same bitmap image are saved. The second version has a higher colour depth.
Explain why the second version may have a larger file size.
Mark scheme
Award up to two marks for a linked explanation such as:
- More binary data is stored for each pixel (1) because a higher colour depth uses more bits per pixel (1)
- Each pixel has a longer binary code (1) so more storage is needed to hold the image (1)
- More colours can be represented (1) so more bits are needed for each pixel (1)
- The file contains more bits in total (1) because colour depth is the number of bits per pixel (1)
For both marks, the expansion must follow/associate with the statement.
Allow 'more bits per pixel' for one mark.
Do not accept 'more pixels' or 'higher resolution' as the reason, because changing colour depth does not change the number of pixels.
Example answers and how they were marked
The second version stores more binary data for each pixel (1) because a higher colour depth uses more bits per pixel (1).
Why: Linked point (1) and reason (1): more data per pixel because more bits per pixel.
The second version uses more bits for each pixel.
Why: One mark for identifying that more bits are stored per pixel; no linked statement about more data or file size.
The second version has more pixels, so there is more data to store.
Why: A common misconception; colour depth does not change the number of pixels, so no creditworthy point is given.