Pixels per inch (PPI) and dots per inch (DPI)

What is PPI? What does PPI/DPI stand for? Does PPI matter?

First off, if you're searching for information on PPI (pixels per inch) or DPI (dots per inch) this probably means you're concerned about how your image will print--perhaps because you've seen a low-resolution warning when making your book.

So here's the most important point when it comes to image resolution: if you see a low resolution warning when making or uploading your book then you must correct the problem.

  • At that point it doesn't matter what the PPI or DPI of your image is. You must fix the cause of the low res warning.
  • You must place the image in a smaller container, zoom out of the image until the low-res warning goes away, or use a different image.
  • You can also choose to ignore the warning but your image may not print well.
  • We do not recommend artificially manipulating the PPI/DPI to make it higher. The printed results may not look good.

Want to learn more about PPI and DPI?

Beyond that, if you're searching for a more general and fuller understanding of what PPI is, how PPI differs from DPI, and what affect it has on your digital photographs in general, below are a few resources which will get you started. Note that these are external sites with no affiliation with Blurb. 

DPI and PPI Explained The author does a good job of breaking things down clearly and succinctly. His idea that "creating pixels is a bad idea" is spot on.

PPI vs DPI: what's the difference? If you'd like to delve deeper into things, this article (aimed at designers but useful here, too) offers additional insight and some helpful visuals.

Basics of Digital Camera Pixels If you want to go further down the rabbit hole of PPI, DPI, pixels and resolution then check out this article from the folks at Cambridge in Colour.

And don't forget...

If you see a low-resolution image warning when making your Blurb book, you must ultimately do one of the following:

  • Place the image in a smaller container.
  • Zoom out of the image (i.e., make it smaller) until the warning goes away.
  • Use a different image entirely.
  • Leave it as-is and take your chances that the image will not print well. We are unable to offer reprints/replacements for problems caused by low-resolution images.

And you might want to give any questionable images the 200% test, too.

 

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