If you’ve done a little research on buying a digital camera, you’ll notice that the higher the megapixel count, the more expensive the camera is. But what are megapixels? How many do you need in a digital camera? Will it be beneficial to you to spend that extra money on a few additional megapixels? Let’s begin with a short 101 about megapixels.
What is a megapixel, exactly?
Good question. Let’s begin by taking out the “mega” and focus on the “pixel”. The word “pixel” comes from “picture element”. A picture element, more or less, is simply a dot. Digital camera images are made up of these dots. One megapixel equals one million dots. Generally speaking, the more megapixels there are, the better the overall quality of an image will be when it’s enlarged.
Below is a picture of my puppy. The first image is the original. The second image was cropped and enlarged. The third even more so…
Notice how the more you enlarge a photo, the grainier it becomes?
For crisp and clear photos, most pictures are printed at a resolution of 300 PPI or DPI (pixels per inch or dots per inch). To determine how many megapixels you’ll need for the size of print you want, you can use this simple formula: multiply each dimension of your photo by the resolution. For example, if I wanted to print an 8x10 photo and my printer resolution was set at 300 PPI, I would simply go (8x300) x (10x300) = 7200000 or 7.2 megapixels.
How many megapixels do I need?
Inexpensive digital cameras and devices which include camera options, such as mobile phones or MP3 players typically have 1-2 megapixels. It will be extremely difficult - if not impossible - to print high quality photos. However, you’ll do just fine if your plans only include emailing photos or posting them to web blogs or personal websites.
In general, these cameras are quite affordable and relatively sufficient for the average Joe. They’ll print optimal photos up to 5x7 or even 6x8.
You’ll get sharp images printing in this range, you can even get wonderful 8x10’s. However, if you are planning to crop and enlarge specific points in an image it might not be enough. For example, if you’ve taken a photo of a bear which turns out to look like a black spec in your image, cropping the bear and enlarging him to a reasonable size will result in a loss of quality and a grainy image.
7 Megapixels and Up
These cameras tend to be rather pricey, so unless you’re planning on printing poster-sized optimum quality photos, anything larger than 7 megapixels could just be throwing money down the drain. Also, keep in mind that more megapixels will require more memory. This means you’ll have to spend more on a larger memory card or settle for only being able to hold very few photos on a smaller card. And as for storage, larger pictures means more space is taken on your computer’s hard drive.
Some Additional Notes to Take into Consideration
Despite the optimal print size for your camera, if you aren’t planning to print photos at this size you are wasting your money purchasing a digital camera with greater megapixels. In other words, buying a digital camera with anything greater than 8 megapixels isn’t going to create better 8x10 photos.
With the above note in mind, don’t forget to leave room for cropping. If you want to enlarge a portion of a photo into an 8x10 it will require more megapixels to get the same results as a photo which hasn’t been cropped.
Making prints at 300 DPI can be overegging the pudding. If you are printing photos for yourself rather than for professional purposes, you can still achieve great results printing at 200-250 PPI. Printing at anything less than this, however, can result in grainy photographs.
Below is a table which illustrates how many megapixels you would need to print a standard sized image at optimal PPI compared to how many you would need printing at 200 PPI. (Click to enlarge)