Image showing the difference between 300 and 72 dpi

Seeing the difference between high and low resolution

Or Why Can’t I Use Downloaded Images from the Internet in My Design?

Okay, so you’re writing articles for your newsletter, you’re going to print 6000 of them and send them to your entire mailing list. You found some great photos and a couple of logos on Google. You stick them in your newsletter, it looks great on screen, then you print your masterpiece on your laser or inkjet printer and…YUCK!

Your text looks great, but everything you got off the internet looks horrible, fuzzy, jaggedy. Now what?

Hmmm. Maybe it’ll look better on the press at your printers, maybe they can do something to clean it up? So you send it off to your printer and they call you the next day, asking if you have higher resolution images. Well, no, you don’t. And what’s the big deal anyway? Why doesn’t it look as good as it does on the screen?

Here’s why.

Resolution refers to the number of pixels (on a monitor) or dots (on a printer or press) per inch. Most monitors show between 72 and 96 pixels per inch. Most laser and inket printers show between 600 and 1400 dots per inch. Here’s how this plays out in the real world. Images on the internet have been saved at a low resolution so they take less time to download when you visit the website. Since monitors only show 72-96 pixels per inch, the images are going to be sized to that resolution. If you print that same image on a printer, that prints at least 600 dots per inch, the computer has to make up information, eight times as much information as it’s been given. Now we get a break on printing because the human eye can’t distinguish more than around 150 dots per inch. (On a laser printer and a press, you need 300 dots per inch on your original digital file to get to 150 dots per inch rendered. There’s a wonderful mathematical formula for this which you probably don’t want to know right now.) Say the image is two inches by three inches. The computer says, ok, I have an image that’s 144 pixels wide by 216 pixels tall for a total of 31,104 pixels. I need more pixels to render as dots on this printer, so I have to add 456 more pixels to the width and 684 more pixels to the height, that’s 311,905 more pixels and a total of 540,000 pixels, (width x height = total number of pixels). That means I’ve got to make 17 copies of each pixel. Now I’m a computer, and I count really well, but when it comes to visual judgement, I’m really stupid, so I’ll just copy each pixel 17 times. In effect, it looks to us humans like the pixels just got a whole lot bigger. And the image looks fuzzier and the edges are really jagged.