Tag Archives: colour depth

Calculations in computer systems

I was sure I had this here already but I can’t find it.

Here are the main formula we used in the computer systems unit

  • Largest number with n bits = 2n-1
  • No of memory locations/different colours = 2n
  • Coloumn heading in a binary number at n bit =2n-1
  • Size of bitmap = no. of Horizontal pixels X no. of Vertical pixels X Colour Depth
  • No. of pixels = DPI X size in inches
  • Total storage capacity = no. of memory locations X location size.

You should also be able to convert from bits, Bytes, Kilobytes, Megabytes, Gigabytes & Terabytes.

  • Bit= 1/0 (Binary digIT)
  • 1 Byte = 8 Bits
  • 1 Kilobytes= 1024 Bytes  (210)
  • 1 Megabytes= 1024 KB  (220)
  • 1 Gigabytes = 1024 MB  (230)
  • 1 Terabytes = 1024 GB  (240)

For colour depth

  • 8 bits = 256 colours (28)
  • 16 bits = High Colour 65,536 colours (216)
  • 24 bits = True Colour 16,777,216 colours (224)

Image sizes

There are plenty of posts on the internet about image file sizes and image file types.

We discussed in class how to calculate image file sizes, however, it’s often hard for raw numbers to mean anything. We forget that file storage was not always the multi Gigabyte size it is now. Here is a way for you to try and get your head around it.

The new iPhone 4s’ camera has a resolution of 3264 by 2448 pixels @ 24 bits per pixel, how many uncompressed images can you fit on a standard 16GB iPhone 4s?