High-res images and the fight against DPI

What is considered a high-resolution image?

You will often hear requests for "high-res" images to be 300 DPI. "DPI" stands for "dots per inch". A dot is just that - a single dot that makes up an image. This is the smallest bit of colour that can be used by the computer to paint a picture. A 300 DPI image will use 300 individual dots every inch to make up the picture. The more dots you have every inch, the higher the resolution. A 600 DPI image has a higher resolution than a 72 DPI image.

Just to confuse things a bit... these "dots" are more commonly called "pixles".

Magainzes and other printed material will often have a requirement that an image be provided at 300 DPI. What you also need to know is how big the image will be when it is printed.

Suppose an image will be printed at a size of 3 inches x 3 inches. If every inch has 300 dots and the image is 3 inches wide, then your image will have a total of 900 dots across. In this example our actual image dimensions would be 900 x 900 pixels.

• 3 inches * 300 dots (pixels) = 900 pixels total

If we use the same example, we start with an image that is 900 x 900 pixels. If the requirement is to provide a picture that is only 150 DPI, then the same image can be use to print a picture that is as large as 6 x 6 inches.

• 900 pixels / 150 DPI = 6 inches

So, the next time somone asks you for a "high-res" image make sure you find out what the printed or displayed size and resolution will be. Multiply these numbers together to find out how many pixels need to be in your image.

Sorry for the math lesson... programs like Photoshop will of course help you out with that part!