We have all read and hear the ads; this camera has 12.2 mega-pixels, this one has 14.4 mega-pixels, and of course the price of the camera reflects how many pixels are on the sensor. The questions arise, "How many pixels do I really need", and "What is a mega-pixel anyway?"
Simply put, a mega-pixel is one million pixels per inch. A pixel is a single point on an image with a particular color and brightness, and by grouping these points together an image is formed. The size of the pixels in relation to the picture determines how sharp the final image will be and how much the image can be enlarged before quality suffers. Take any image and zoom in enough and soon the pixels will be visible as blocks of color or shades of gray. The size and amount of pixels in an image also contributes to the size of the file.
With the many choices available, pixel quantity is a major factor in determining what camera is purchased, and by listening to the ads, only the most will suffice. In actuality, the most important thing to consider when buying a camera is what it is going to be used for. If you plan to make poster size pictures to hang on your wall, then yes, the ads are correct and you should spend the money for at least 14.4 mega-pixels, if not more. However, if you have a blog and want to post pictures to it, or any website for that matter, than 14.4 is extreme overkill; in fact, any camera you buy today will be extreme overkill for web-based pictures. Screen resolution is listed as horizontal pixels X vertical pixels per inch, so a screen set at 1280 X 1024 will have 1,310,720 pixels per inch, or just over 1.3 mega-pixels. Any higher resolution will be lost as the computer translates the file into an image to be viewed on-screen, and the wasted file size will slow the file transfer, especially when sending via email. The same goes for digital picture frames which usually have an even lower resolution than a monitor.
Other factors need to be considered along with pixel quantity. ISO measures the light gathering ability of the sensor, and a higher ISO allows photos in lower lighting environments, but with a loss in picture quality; with a higher ISO, the pictures will start to look grainy and the colors will be less vibrant. Most point and shoot cameras have a preset ISO setting, usually 400, and a camera with adjustable ISO is more expensive, but frequently worth the extra price. Of course, the optics are the most important feature of a camera, either film or digital, and no matter how many pixels the camera has, if it has poor optics, the only result will be very faithfully rendered blurry pictures.
"Mega-pixels" is the current sexy byword for camera manufacturers and retailers, and while important, it is only one facet which must be considered with any digital camera purchase. More importantly, having a good idea as to how the camera will be used is the most important datum in deciding what camera to buy.