When it comes to images in print — specifically photos, the difference between screen resolution and print resolution is very important to understand.
We are often asked to pull logos from websites or images from Facebook for print pieces, but more often than not, the resolution is simply not high enough to render a decent print product. Let’s look at the reason why this typically doesn’t work.
Take this scenario. You look at an image on screen and it looks fine, but printed at the same size it looks pixelated — why is that? That is because screen resolution is different from print resolution.
Though technology is advancing rapidly and higher screen resolutions are available on some devices, the standard screen resolution is still 72 DPI (dots per inch) or PPI (pixels per inch) where standard print resolution is 300 DPI.
Based off of those numbers, some simple math will tell us that 2 inches on screen is 124 dots (2 x 72 = 124), while 2 inches in print is 600 dots (2 x 300 = 600).
Therefore, assuming one dot on screen is relative to one dot in print, 2 inches on screen (124 dots) is NOT equal to 2 inches in print (300 dots).
Here's a little rule of thumb...
2 inches on screen = 0.48 inches in print
Here's a common misconception:
"My image is 72 DPI, but I can just change that to 300 DPI right?”
Unfortunately not. On a rasterized file (meaning an image based on pixels), dimensions are predefined. Therefore, you cannot simply raise the resolution. All that will do is stretch the pixels that already exist, thereby resulting in a very muddy image — as seen above.
The bottom line
In print, specifically with photographs, you need high resolution images to ensure a clean print piece. Just because it looks good on screen, doesn’t mean it will print well at 300 PPI.
Check your image resolution to see how many pixels wide it is, then divide that by 300 to determine how many inches wide it can be in print. For example, an image that is 600 pixels wide, would render a 2 inch image in print.