There is a vast amount of information on the internet regarding megapixels, image resolution, screen resolution, and print quality. This page is designed as a quick reference to simplify all of that information. So, here we go. We will start with simple definitions.
• Image Resolution
Resolution is how many pixels you have counted horizontally or vertically when used to describe a stored image.
• Print Resolution
Resolution is also how many pixels you have per inch or other linear unit when you print on paper. Most prints are made at 300 pixels per inch (PPI or DPI, dots per inch).
• Screen Resolution
Most computer screens today are 72 DPI, dots per inch. There isn’t much variation from screen to screen. Most computer screens are about 1,024 x 768 pixels. All HDTV’s, no matter what size, 32″ or 60″ have a screen resolution of 1920 x 1080 pixels. Hence 1080p.
Pixel Count, expressed as Megapixels, is simply multiplying the number of horizontal pixels by the number of vertical pixels. It’s exactly like calculating area. A 3 MP camera has 2,048 (horizontal) x 1,536 (vertical) pixels, or 3,145,728 pixels. We call this simply 3 MP.
• Understanding Megapixels
Every digital photo is composed of pixels–millions of them. Pixels are an easy thing to measure, so many people buy a camera that captures a lot of them, assuming that more pixels equals better quality. As any camera advertisement will reveal, cameras are typically rated by the megapixel, which describes how many millions of pixels are embodied in a photo. A 1-megapixel camera takes photos with a million pixels in them; a 20-megapixel camera captures 20 million pixel photos. Think of it like a grid that tells you how wide and tall the photo is. Consider the Nikon D7000, a 16-megapixel camera. It takes photos that are 4928 by 3264 pixels. Multiply those two numbers, and you get about 16 million. Compare that to the Apple iPhone 4s, which takes photos that are 3264 by 2448 pixels: 3264 times 2448 is about 8 million, or 8 megapixels.
• Megapixels VS Image Size
This list gives approximate image sizes for 2-70 Megapixel camera images.
◦ 2 MP = 1600 x 1200 pixels
◦ 4 MP = 2272 x 1704 pixels
◦ 6 MP = 2816 x 2112 pixels
◦ 8 MP = 3264 x 2448 pixels
◦ 10 MP = 3648 x 2736 pixels
◦ 12 MP = 4096 x 3072 pixels
◦ 15 MP = 4480 x 3360 pixels
◦ 20 MP = 5120 x 3840 pixels
◦ 40 MP = 7216 x 5412 pixels
◦ 70 MP = 9600 x 7200 pixels
• Image Size VS Print Size
So what print size and print quality can you expect from your images? Here are some suggested minimum image resolutions for standard print sizes printed at 300 dpi. Remember theses are minimum digital image sizes. Higher resolutions offer more room for cropping and better results.
◦ For a wallet-size print, the image resolution should be 640 x 480 pixels.
◦ For a 4″ x 6″ print, the image resolution should be 1024 x 768 pixels.
◦ For a 5″ x 7″ print, the image resolution should be 1536 x 1024 pixels.
◦ For an 8″ x 10″ print, the image resolution should be 1600 x 1200 pixels.
◦ For a 16″ x 20″ print, the image resolution should be 2272 x 1704 pixels.
◦ For a 20″ x 30″ print, the image resolution should be 2816 x 2112 pixels.