Size Up The Camera

• So you're torn between buying a 6MP (MegaPixelA term used to describe how many million pixels a camera can output an image at.) and a 10MP camera? Or maybe not, because everyone tells you that more megapixels is better, right? Perhaps you've even heard that no-one can print good photos at a mere 3MP. Well, let's have a look at what figures actually mean in the real world.
• Mega is another way of saying million, so a 6MP camera can output a photo containing 6 million pixelsIn digital imaging, a pixel is the smallest piece of information in an image. Pixels are normally arranged in a regular 2-dimensional grid. This is calculated by multiplying 3,000 x 2,000, i.e we now know that the photo's long edge will have 3,000 pixels, the short edge 2,000.
• Going back to our publication standard resolution, talked about on the Photo Resolution page, which is generally 300 pixels per inch, we can see that 3,000 x 2,000 pixels would give us a 10 inch by 6.7 inch photo! When was the last time you saw a photo album with sleeves that big? A film processing company produces standard prints that are perhaps 7 inches by 5 inches. And if you displayed a 6 megapixel image at screen resolution (let's say 100 pixels per inch), you'd need a 30 inch by 20 inch screen to fit it on.

Quality Not Quantity

• We've seen that even 6 megapixels could be considered overkill for the majority of home camera users. I've produced perfectly good photo prints for framing using a mobile phone's 3MP camera. What spoils most photos is not the actual resolution, but it's the quality of the sensor in the camera taking the photos.
• We'll have a look at the differences in sensors in our Sensorble Cameras article, but there are vast differences between what a point-and-shoot and what a digital SLR camera can output, even at the same megapixel count.

More Can Be Less

• Consider this though. Assume we have two Costa Notalotta cameras next to each other, one is advertised as a 6MP camera, the other as 10MP. They both have tiny lenses, of course, and inside, unseen by us, they also have tiny sensors for picking up the image. That's why they're small and cheap. Both sensors are the same size, but one has 6 million little pixels squashed onto the sensor, the other 10 million.
• In broad daylight, both cameras probably perform perfectly well. But along comes dusk, and what happens? The much tinier squashed pixels on the 10MP sensor can't really see what's happening out there, as they're not big enough to pick up any light now. But the slightly larger and less squashed 6 million pixels on our 6 MP sensor struggle a bit, but as they're bigger, are able to make a better job of seeing something.
• This sums up the whole problem of fitting more pixels onto a sensor which stays the same size - the resolution may be higher but the quality drops off much faster in low light, and indeed also with smaller lens apertures. Digital SLR cameras, it must be added, suffer from this problem too, but they have much larger sensors and lenses, so they can have resolutions of 10MP before starting to see the drop off in quality.