What one thing does NEARLY EVERY photographer misunderstand? DPI. ("Should it be 300? 72? And what is PPI? Are they the same thing?")

What Are DPI & PPI?

First, definitions:
DPI is what printers use - how many dots per inch are printed on the paper.
PPI is what screens use - how many pixels per inch are displayed on your monitor.

They Shouldn't Matter To You

Did you know that neither one of these things matter in the files that you save? It's true. The only thing that matters is how many pixels are in your image.

Let's say your camera produces a 6000 pixel x 4000 pixel image. Unless you need to crop some stuff out, those are exactly the dimensions of the file that you are going to send the printer.

Yes, Lightroom and Photoshop do let you set DPI/PPI resolution. People will tell you that it is important to set this: 300 DPI for printers, and 72 DPI for screens. Please understand me: It. Doesn't. Matter. It makes zero difference for anything.

Test It for Yourself

Don't believe me? Do this to your 6000px x 4000px image:

• Set it to 300 Pixels/Inch and save
• Now set it to 72 PPI and save it again
• Set it to 10,000 PPI and save a third version
• Set it to 1 PPI and save your fourth version

Now look at all four files. They are the SAME file size, the SAME number of pixels. They are all identical files - there is NOTHING different about them (other than a meta data field you can't see).

Now put them all onto a page in InDesign and print it on your 600 DPI inkjet. Yep, they all look exactly the same. This is because your image file isn't what determines how a printer sets its print resolution. Your image file just provides the pixels.

It's Not a Printer Problem Anymore

You see, unlike the early days of desktop publishing (yes, I was there at the beginning), modern printers don't care* what PPI or DPI you save the image at, as long as there are enough pixels to print what they need.

If they're printing a nice photo or magazine, that 6000-pixel-wide image can be printed 20 inches wide beautifully at 300 DPI. That same photo can also be printed on a 25-FOOT-wide billboard printed at 20 DPI. Using the same exact file. And it will not have mattered what DPI you saved it as.

What Should You Send to Clients?

Regarding what file sizes to deliver to your clients: That's also about pixel size, not DPI or PPI. Social media sizes are 2048 pixels on the longest edge for Facebook and 1080 pixels on the longest edge for Instagram (or 1350 pixels tall if uploading a vertical photo with a 4:5 aspect ratio). If you want to deliver to your client the best possible Facebook photo, or ensure that your stuff always looks the best it can on Facebook, check out this article.

* Even though you now know DPI & PPI don't matter to your files, you should still make sure that you're submitting files to requested spec. It'll save you a bunch of back-and-forth with the printing company employee who doesn't know anything besides what they were trained to watch for 20 years ago.