A simple explanation to this question would be: The more megapixels (MP) your camera offers, the more detail the image will have and the sharper it will become; especially if the image is given the proper exposure and focus at the highest MP setting.
Mega Pixel:
Digital photos are made up of tiny dots called pixels. Each of these pixels carry a small amount of information that defines a color. So to create a digital photo, we put hundreds and thousands of these dots together to create a recognizable image. To define megapixels, it is the number of pixels in the millions and is calculated as the number of pixels across an image multiplied by the number of pixels running down an image. An example: 3000 pixels (W) x 2000 pixels (H)=6,000,000 pixels
(See diagram on left). This will translate as a 6-megapixel photograph.
Resolution:
Now that we understand what a megapixel is, how does that factor into the quality of a photo?
The term we use to measure quality of a digital image is called resolution. There are two types of resolution that we commonly refer to, print resolution and screen resolution. Resolution is measured in Dots-Per-Inch (DPI). Which is the same as saying, pixels per inch. That is how many pixels you can fit into an inch of space. Logically speaking, the more pixels you can squeeze into an inch, the more information you can capture within that 1-inch area.
Screen Resolution:
For regular photo viewing online or on your desktop, there isn’t much of a quality difference whether you are displaying an image that is 3 MP or 10 MP. Computer monitors are normally designed to display at 72 to 100 DPI. That’s the physical number of pixels your screen is able to display per inch. It won’t display any more information even if your photo is at 10 MP. For most monitors with the highest resolution display setting at 1920 x 1200 (equivalent of a 24-inch monitor), a 3 MP image will sufficiently fill up the entire screen displayed at 100% (See diagram on left).
Print Resolution:
Megapixels plays a big role when it comes to print resolution. Standard print resolution is set much higher than the screen resolution. For a standard quality photo print, a minimum 200 DPI is required. The ideal resolution will be 300 DPI. This means that the maximum size of your high-quality photo prints are limited by the megapixels. For example, with a lower megapixel camera, say at 2.16 MP, the largest photo size you can yield will be a 4 x 6 photo, printed at 300 DPI for highest quality. If you choose to print a larger size than 4 x 6, such as a 5 x 7, you’ll start to see a degradation in the sharpness/clarity in the photo. This is due to the fact that your DPIs are being rationed out to fill up those extra inches. Less dots-per-inch basically means, less information per inch. Less information per inch translates into “less sharpness” for you photo.
See the example below for how the difference in DPI can effect the quality of a printed photo.
Megapixel quantity isn’t the primary factor that effects photo quality. The lens you use and the sensitivity of the imaging sensor in your camera will also determine how well your photo will be captured. When a photo has more megapixels it usually gives you more prints sizes to choose from, while still retaining quality. That’s why you can never have too many megapixels. You can always size down a photo and still get a sharp photo. However, you will not get the same results when you size up from a smaller photo. One of the drawbacks to having more megapixels than you need is you are stuck with a larger image file size. A higher megapixel camera usually means you need a larger memory card or hard drive to store your photos. However, in my opinion, I think it is a good trade off. You can always buy an additional hard drive to accommodate your image files. Though you can never buy more quality for photos that you’ve already taken with a lower megapixel camera; especially for those once-in-a-life time photo moments.
