An Introduction to Megapixels and Their Affect on Photos

Megapixels Are the Building Blocks of Digital Photographs

Camera manufacturers are fond of advertising cameras by the number of megapixels they have. This sounds great in marketing, but what exactly is a megapixel? How do they affect your photos? How concerned should you be about buying more megapixels in a camera? 

What is a Megapixel?

One megapixel is 1 million pixels. Pixels are small squares that are put together like pieces of a puzzle or a mosaic to create your photographs.

The resolution of your image will be determined in large part by how many of these tiny squares are packed together in a small space.

  • A 20-megapixel camera (20MP) would have roughly twenty million tiny squares of information per inch.
  • A camera phone with 8-megapixels (8MP) would only have eight million squares of information in an inch.

So what does that mean for your photos?

Simply put: more megapixels means more information and that leads to higher quality images.

The more information that is squeezed into an area, the easier it is for our eyes to blend the edges together to create a complete image. If too little information is available, the eye will notice the jagged edges of the pixels where they meet, just as you see the individual squares of mosaic tile designs.

The accepted "standard" for printing images is 300dpi (dots per inch). While dots per inch aren't technically the same as pixels per inch (ppi), the difference won't affect you in your day to day photo taking and printing.

How much information do I need?

To figure out how much information you need for a specific print size, all you need to do is multiply the print size by the resolution desired.

For example, to print an 8x10 photo you would need 2400 pixels by 3000 pixels of information at 300dpi. If you were displaying an image on the internet (where 72 pixels per inch is acceptable) you would only need 576 pixels by 720 pixels.

So how many megapixels do I need?

Each camera displays data in slightly different ratios but there are some "rules of thumb" you can follow.

  • Decide the largest size image you will want to print. For most people,  this will be an 8x10 image.
  • Determine the number of pixels needed for a 300dpi print. For that 8x10 print, this is 2400x3000.
  • Multiply the two pixel dimensions together. For an 8x10 this comes out to 7.2 million pixels (7.2 megapixels). This is the preferred number of MP you need if an 8x10 print is the largest you are likely to print.

Are You a Megapixel Chaser?

Some people enjoy grabbing the latest and greatest technology as soon as it's released. This is great, but when it comes to the reality of digital cameras, you do not always have to 'chase' the megapixel and upgrade to a higher megapixel camera.

As you can see by the math, the majority of cameras (and even most cell phones) have more than enough MP to make a decent 8x10 print. Pretty much anytime after 2013, it actually became difficult to find a new digital camera below 7.2 megapixels. With each new year, the megapixels are increasing, so there really is no need to worry about megapixels or grab a new camera just to say you have more MP than your friends.

What does matter in photography - and it always has, even with film - is the quality of your lenses and your ability to capture a proper exposure. Factor in the quality of a digital camera's sensor and you should have no problems getting great looking photographs.