“Ay, there’s the rub,” as Shakespeare said. It would seem that the more pixels your camera has, the more resolution it would have and, therefore,the more detailed your images would be with a gentler, more natural gradation of tones. Unfortunately, this is not necessarily true. In fact, too many pixels can actually begin to degrade image quality.One of the problems with putting more pixels onto a sensor of a given size is that each pixel must be smaller. That is a significant issue.Cramming more pixels onto a sensor introduces the issue of digital noise— a type of image degradation that looks similar to excessive film grain.Noise is created by the electrical interference between pixels, as well as the higher level of heat that more pixels generate.
The more pixels you have on a given sensor, the more noise your images will have.In addition, the smaller a pixel is, the less sensitive it is to light (larger pixels are, by their design, more sensitive to light). This means that small-sensor cameras that have more pixels almost always produce noticeably noisy images at higher ISO speeds. This is not necessarily true if you are using more pixels in a camera with a larger sensor. The larger sensor size allows for larger individual pixels and more space between them.Also, not all pixels are created equal.
There are differences in quality of craftsmanship, so more pixels is not an indication that they’ll perform better. In addition, there are other factors at work, including the quality of the lens you’re using. All other things being equal, if you put a high-quality, professional glass lens on a 6-megapixel camera and a terrible plastic lens on a 12-megapixel camera, the lower pixel count with the better lens will produce the better image.