Close-up of a CCD camera chip

There seems to be an increasing obsession amongst mobile phone users about the number of pixels the camera has, in what has become many people’s primary method of communication (I can’t remember the last time I wrote a letter!).

Facebook and Twitter aside for the moment, most of us text and phone *lots*

But what about the camera that comes with our phone? Well, I enjoy posting photos on Twitpic, Facebook etc – but do I need an 8 or 12 megapixel camera to do this? And are more pixels necessarily better?

The simple answer is “No” and “No”.

Let me explain why – and if you think about it, the answer is quite obvious. The main factor that contributes to the quality of your final image is the size of the lens that’s in front of the imaging chip (aka ‘CCD Chip’ for the supernerds like me).

The CCD chip in the photo here is normally attached to a lens which is about 10cm across. That’s around 20 times wider than the lens on your average cameraphone. This chip is actually used to take colour photos of the night sky and the lens is at the front of a 4 inch diameter telescope. The images are great, and that’s mainly because the lens can gather lots of light. Unlike the average cameraphone.

There are two other important factors that determine the image quality too: the size of the tiny pixels that make up the chip, and the quality of the hardware that turns the signals produced by the CCD chip into shades of grey and colour in the final electronic version of the original object.

If the pixels are too small, the chip won’t be very sensitive to low light levels. If the pixels are too large, then the images will quickly appear blocky when they blown up to A3 or A2 size.

It turns out that the total size of the chips in most cameraphones is more or less the same – this is because the lenses have to be quite small to fit into the camera body.

So, if you have a cameraphone with more pixels – eg, an 8 megapixel camera instead of a 5 megapixel camera, for example, the former CCD chip might have smaller pixels. So it could be less sensitive to light. And images in low light can quickly appear very ‘grainy’, which isn’t particularly nice to look at.

In bright light, a less sensitive CCD chip will need a slower shutter speed in order to gather the same amount of light that a more sensitive camera will pick up with no problem. So a less sensitive camera will be more likely to blur.

In reality, of course, it isn’t as straightforward as this, because an awful lot happens in the camera’s hardware to clean up the images, and compensate for sudden movements (ie  ‘camera shake’).

So, before you shout yah-boo at 8 or 12 Megapixel cameras, just remember that the manufacturers are well aware of these issues too, and will think of all sorts of clever ways to squeeze as much quality out of the original light hitting the CCD chip as possible.

But the takeaway thought is this: Don’t get obsessed with megapixels! It’s mainly a marketing tactic to get us to upgrade sooner, so please don’t fall for it, OK?

When are you getting your Nokia N97?