In years, we have been bombarded by advertisements of photographic cameras, especially digital compact ones, focused on a real challenge among products, leaving the impression the better is always the one with more Megapixels overall. This could seam to the public a numeric increase that simply follows the growth of the technological progress, but in other words it is merely a commercial speculation lacking of any foundation.
A Megapixel corresponds to a million of pixels. The term pixel comes from the contraction of picture and element and defines the point elements composing the digital image. The quantity of pixels only defines the dimension of the image and, consequently, its maximum print dimension. For example, if the quantity of pixels is 6 Megapixels (the approximate equivalent of an image of 2000×3000 pixels), it means that the image is professionally (300 dpi) printable in the maximum size of 7,87×11,81inches and homely (for example, 100 dpi) 1feet+7,69inches x 2feet+3,56inches maximum, before starting to lose definition.
The image definition is not due to pixels, or Megapixels, but to the quality of lens and the size of sensor, our film. If the lens is poor quality, the image is low quality and not well-defined, irrespective of the quantity of pixels. Absurdly, if you have a low quality lens, but a high number of Megapixels it simply means that it will be possible to print in big size an image that however will remain low quality and not well-defined! Furthermore, an image with many pixels occupies a lot of memory.
Let’s do some practical examples. WQXGA monitors, like the latest generation televisions, higher than full HD, have 2560×1600 pixels of resolution, equal to 4 Megapixels circa. So, if we only use our digital images for display visualization (web sites, social networks, blogs…) and for small size prints too, few Megapixels will be enough.
A further and current example is the advertising of one of the latest Nokia smartphone: Nokia Lumia 1020 with 41 Megapixels. It means that commercial prints (100dpi) of 6feet+6,74inches x 4feet+3,18inches circa are possible. In your opinion, is it possible to print a well-defined billboard from an image taken with a mobile phone with a lens of few inches? This is why, my advice for the amateur who has got a photographic camera with 5-6 Megapixels is to evaluate the lens and the sensor more than the quantity of pixels.