AirToob Lightning
What we take for granted...

I have spent a couple of months (not full time!) producing a free online Guide to the Sony Cyber-Shot DSC-RX100 II, the rather extraordinary compact camera that I have been using since November 2014.

I did this mainly as a learning exercise, since the existing online information about it is not too helpful for non-experts new to the camera (or to similar cameras).

I have just updated the guide, and was struck when adding a new section by how much we take for granted the technology that gives us gigabytes of cheap, compact storage, and the way in which we use it.

For instance, each photo that I take is a collection of nearly 20 million pixels, each of which (if the image were represented as a normal bitmap) would have 256 possible values for Red, and the same for Green and Blue. The storage for such a bitmap would take nearly 60 megabytes (60MB). Luckily this can be compressed to take up much less room, thanks to the work of the JPEG, the group of experts whose techniques give their name to the familiar .jpg or .jpeg file.

I think of JPEG compression as essentially storing only the differences between pixels (an image filled with a single colour would require very little storage as a jpeg), but that's only part of the story. Probably only real mathematicians (not me) and human vision specialists (definitely not me) fully understand how the compression really works.

Instead of images, the illustrated tiny card could hold something over 50,000 eBooks (represented and compressed as described here), each of which probably took someone at least a year to write, making a collection that would take well over 100 years to read at a rate of one book a day...

Just for fun... what would a megabyte look like, if you could see the bits?

Well, to start with, a megabyte is 8*1024*1024 bits, or just over 8,000,000 bits (each of which can store a value 0 or 1).

Imagine that the image to the right is a tile 1cm square, and the white dots (100 of them) are bits. Then you could lay 100 of these tiles out in a row, and then add 99 more rows below that, and you would end up with a bigger tile 1 meter square, or a little over a square yard (about the size of a carpet tile, as it happens). That “electronic carpet tile” contains a million “bits”, so you would need just over 8 “electronic carpet tiles” to get a “megabyte”. That's enough to carpet a small bedroom in an English house, storing 100 bits in each square cm, or about 645 bits per square inch.

The storage for a single typical .jpeg image file, to use this strange (but fun?) analogy, might be represented by 50 of these “electronic carpet tiles” - enough to cover the floor of a good-sized living room.

OK, so if we used the “electronic carpet tile” analogy, what would the 32GB contained in that chip look like? Well, 32GB is 32*1024 megabytes, so we would need to lay out around 270,000 one-metre-square “electronic carpet tiles”... enough to cover nearly 38 professional football fields.

Moving up...

I see that today I can buy a 1 Terabyte internal hard drive for about £37. That's around 8,388,608 one-metre-square “electronic carpet tiles”, an area of around 8.4 km². Heathrow Airport currently covers an area of 12.14 km², so we are looking at enough one-metre-square “electronic carpet tiles” to cover more than two-thirds of a large airport.

When I first worked with computers, each bit was a ferrite ring, of about the same dimensions as one of those tiny white squares. I remember watching women in the assembly shop making "core store units" by threading 3 fine wires (if I remember correctly) through each ferrite ring. The biggest such unit would have been only 96KB in today's terms - and oddly enough, that was big enough to do some serious radar processing and produce a display on one of those big round screens you see today in air traffic control centres. (Those were the days when every line of software in the computer did useful work for just one application.)

[ ...and the old dinosaur mooches off into the distance, shaking his head ]