If you are using a digital camera and/or your images are intended primarily for print, this article will help you to understand the relationship between megapixels, resolution, and image size.
Let's start with a basic definition: What is a pixel? Pixels are individual points of color in a digital image.
Compare to the crowd at a sports stadium, each with a different colored card. Individually each card is simply a square piece of color, but when everyone in the stadium holds up their cards, together they form an image. This is exactly how pixels work in a digital image. Each individual point is only a single color, but placed together they can be used to form images.
If you're working with a digital camera, chances are you know what the megapixel count is. From there it's a fairly simple process to calculate the width and height of your camera's resulting images. We're going to be using an imaginary 12 megapixel digital SLR for the purposes of demonstration.
STEP ONE
The first step will be to find out the aspect ratio of your camera. Most modern digital cameras use either a 3:2 ratio for SLR cameras, or a 4:3 ratio for point-and-shoot types. Your camera may also allow you to select from more than one ratio. You should be able to find the ratio in your camera's Settings menu.
Smartphone cameras vary between manufacturers. Some allow you to choose from multiple aspect ratios in the stock camera app, others do not but there are a number of apps available for both iOS and Android that allow you to set the aspect ratio. For the stock phone camera app, 4:3 is the most common.
For the purpose of this tutorial, we will set our imaginary 12 megapixel SLR to a ratio of 3:2. What that means is that our camera's images will have 3 horizontal pixels for every 2 vertical pixels.
STEP TWO
Convert your megapixel count to a total pixel count – multiply your camera's megapixel count by 1 million. For our 12 megapixel camera that comes out to 12 million.
STEP THREE
Determine the horizontal-to-vertical and vertical-to-horizontal ratio for your camera's ratio. To do that using our camera's 3:2 ratio:
For the horizontal-to-vertical ration, divide the first number by the second.
3 by 2 = 1.5.
For the vertical-to-horizontal ratio, divide the second number by the first.
2 by 3 = .667
STEP FOUR
Multiply your pixel count first by the horizontal-to-vertical ratio, then separately by your vertical-to-horizontal ratio:
12,000,000 x 1.5 = 18,000,000
12,000,000 x .667 = 8, 004,00
STEP FIVE
For this next step, you can use a calculator to make it easy. Take the square root of each of your resulting numbers:
18,000,000 = 4243
8,004,000 = 2829
STEP SIX
You now have the resolution for your digital camera in pixels. In the case of our imaginary camera, that means the camera's images will come out at 4243 x 2829. Now we know that our 12 megapixel digital SLR at a ratio of 3:2 produces images with pixel dimensions of 4243 x 2829.
Click here for information on how to convert between print size and pixel dimensions for uploading your images.
Leave a comment
0 Comments