What are megapixels?
When you take a picture with a digital camera it is made up of millions of tiny dots called pixels. Pixel stands for PICture ELement and if you put them close together you can get a decent picture. If you magnify an image enough you’ll see the dots quite clearly – they’re just like building blocks for a picture. The word mega means a million – hence megapixels means millions of pixels.
When you read about image resolution it’s all about how many megapixels you have. Basically you multiply the number of pixels along the width of the picture by the number along the height. So if your image is about 4000 pixels wide by 3000 high you end up with 4000 x 3000 pixels or 12 million pixels or 12 megapixels – simple! These figures are quite standard for a modern 12 megapixel camera.
So if you want double the resolution you’d need 24 megapixels? WRONG! To double your linear resolution you would need double the pixels along the width and the height. In other words, you’d need 8000 x 6000 or a whopping great 48 megapixels!
Camera megapixels explained
The bottom line is that sales people will often hoodwink you with figures. You know the sort of thing – “this 12 megapixel camera is much better than the 10 megapixel camera – look, it’s got a whole 2 million more pixels.” Now do the maths – to get 10 megapixels you need 3650 x 2700 pixels which really isn’t that much less than the 4000 x 3000 we started with. To be able to actually notice the difference you need a much larger increase in the number of megapixels.
How many camera megapixels do you actually need?
To be brutally honest, if you just want to print out the odd 6 x 4 inch print or post a few pictures on social networking sites then a 4 megapixel camera would do just fine. However as technology progresses, more megapixel cameras get cheaper anyway but should you just go out and buy bigger and better? 12 megapixels allows you to do decent A3 prints and as we’ve seen, to get much better than that you really need 24 and more. We do commercial work and social photography with SLRs and find 12 megapixels really is quite adequate for double page magazine spreads and wedding albums.
Problems with more camera megapixels?
You see, just going for more camera megapixels is not always a good thing. There are two things which will always operate against you:
1. Image size. Yes, that’s right – you want a bigger image? Then make sure you get the computing power needed to store it. You can’t fit many 20 megapixel images on a 4 Gb card.
2. Image noise. What we mean here is those little randomly coloured dots you often get when trying to take pictures in low light conditions. Maybe the images are too grainy? As you try and jam more pixels onto a fixed size sensor in a compact camera then they will generate more heat and cause some disruption in the way the image is recorded. This is image noise. You can’t keep packing them in because the image quality will actually decrease. You cannot break the laws of Physics!
The bottom line is that 10-12 megapixels is a great compromise. You’re at the high end of today’s digital compacts but not so high that the laws of Physics take over and start degrading your images.