Many people when it comes to buying or rating a camera, phone, tablet or device allowing a photograph, the first thing is fixed is in the number of Megapixels that has and not in, for example, the sensor size. As apology should be noted the relentless advertising mantra years ago in manifesting that importantly were megapixels to get a better picture. Thank goodness that it seems that now that fashion has ceased, at least in part.
And if they are not the Megapixels, which is what matters? Thus, for example, the sensor and, above all, its size. One of the aspects to take into account when buying a camera should be the sensor size.
Size vs megapixel sensor
A photo sensor is made up of millions of tiny silicon semiconductors, photosites, that makes the incoming light (photons) into electric current and each photosite corresponds to a pixel or point. It should be deduced, then, that most points have greater sensor image quality will be photography. The predominant technologies on the market are CCD and CMOS.
On the other hand, the megapixel or million points is the unit of measurement of the resolution of a sensor. They are the number of pixels that form the image generated on the sensor. For example, the image of a Canon EOS 6 d consists of 5472 x 3648 pixels = 19.961.856 or what is the same, rounding, 20 megapixels. How much more megapixel our sensor has greater level of detail will obtain, thus may be older paper copies, or make cuts in the image.
As a general rule, the bigger the sensor, more final quality will have the image. Then, why not all devices choose the larger sensor? There are several factors, the first is the price, great sensors tend to be more expensive; the second is the size, a full-frame sensor does not fit into a mobile phone, for example.
In the web cameraimagsensor the sizes of sensors of different devices that can shoot photos can be compared (the first three that are almost not read are Apple ipad 3, Apple iphone 6 Plus and Canon Powershot SX40 HS):
To clarify the question we need to incorporate two terms more to the relationship between megapixels and the size of the sensor, which would be the pixel size and density.
The pixel density It would be the number of pixels that has divided by its surface sensor, normally expressed in megapixels per square centimeter. And the pixel size It is the length of the photosite, which is calculated by dividing the length of the sensor by the length of the image pixels, expressed in microns (thousandth of a mm).
The smaller the pixel density, the greater the size of these and, therefore, better image quality, with the same sensor size. I.e., if we have two cameras with the same sensor size and that they are of the same generation (cannot be compared equipment including long time has passed), will have higher quality image that has fewer megapixels, you will have a lower density of pixels, and these will be larger, capturing more light and offering more detail. Or, if we want it to see otherwise, equality of megapixels, the image will be better in a camera with a larger sensor (less pixel density).