The 24-megapixel A7 was already the world's smallest and lightest full frame compact system camera, and it was joined by the 36-megapixel A7R and high-sensitivity A7s. 

So here's our guide to the whole digital camera market, the different camera types available and what to look for, because once you break them down into just three main types, it all starts to get a lot simpler. They are: