First things first, let’s define our terms so we know what we’re talking about. Unfortunately, DPI is often used simultaneously to refer to two distinct topics. While both describe DPI as Dots Per Inch, we must recognize the difference between a printer dot and a pixel dot.
Because of this confusion, it’s important for us to set things straight. In our field, many creators wonder “Is DPI the same as PPI?” Let’s begin with an emphatic: no.
In this article we will be using DPI to refer to Printer Dots Per Inch. Conversely, we will be using PPI to refer to Pixels Per Inch. Thankfully, industry leaders like Adobe have also adopted this distinction.
Raster images are made up of any number of pixels. When we print them, we naturally are printing at some specific pixel density. And when we set up our print job, the settings need to match. We are selecting a size of the image and resolution that reflects the number of ink droplets used to print the image.
A common use example would be printing a raster image at 300 PPI (pixels per inch). In this case, using a printer dot resolution of 1440x1440 would print the image perfectly.
Pixels Per Inch (PPI)
You may have heard that 300 PPI is the standard for printing. This has a lot of truth to it, but it’s not a steadfast rule. And learning when it’s appropriate could save you from making some errors in pre-press. There’s nothing worse than guessing at your PPI for printing only to have to re-run the job.
Roughly speaking, 300 Pixels Per Inch is a standard where the print looks nice and detailed even when you have your nose up to the piece. Any less than this minimum resolution and you run into trouble. But meet the need and your audience won’t notice any artifacts, blurring, or worse.
This is usually the goal with fine art prints – a size and resolution that match perfectly. Printing with a lower resolution will mean that your image is either pixelated or blurred. Obviously, most printmakers will want to avoid that to maintain the integrity of the original image’s print.
Printing with a higher resolution, which is an option on most fine art printers, will produce details you may need a loupe to notice. This is generally recommended when printing from vector sources (like a text layer in an Adobe Photoshop document).
However, not every print needs to be up to those high standards. Consider a billboard, for an extreme example. Standard billboards run 14 feet high and 48 feet wide.
At 300 pixels per inch, that’s 50,400 pixels tall and 172,800 pixels wide. Certain elements like text and logos can be vector and will scale up infinitely. But as far as photographic images go, best of luck trying to find source or stock images that are 50,000 pixels tall.
For a billboard, that doesn’t matter. Lower printer resolution images can be easily blown up with little issue. This is because nobody’s putting their nose up to one; they’re viewing them from hundreds of feet away.
The same is true, to a smaller extent, with signage and décor printing. For commercial printers, the client’s satisfaction is going to trump an insistence on never printing below 300 PPI. Sometimes a graduation or family photo will need to be blown up. Or sometimes the client needs something on a wall graphic where perfection isn’t the expectation.
Optimal PPI for Printing Settings
Here’s a general guide to knowing what you can get away with vs what will be pixelated or blurred:
- Design at 600 PPI – Looks okay through a loupe – text in particular
- Design at 300 PPI – Looks okay with your nose to the print
- Design at 180 PPI – Looks okay from about a meter away
- Design at 100 PPI – Looks okay from about two meters away
As you can see, PPI and higher quality are all relative. The best resolution for printing really comes down to how closely the image will be observed by the human eye. The further from the image you or your audience will be, the more covered you are. And, intrinsically, the lower the printer resolution can comfortably be set at.
Beyond these benchmarks, your results may vary. The best way to know what looks good in a specific location would be to make your own prints and judge for yourself. A hard proof may be a good idea. With this in hand, your customers can understand the possible quality of the image from a given source.
Printer Dots per Inch (DPI)
The key difference between a printer dot and a pixel is important lies in the process itself and how the printer handles each one.
Remember that a pixel refers to a single square of color on your computer screen. Meanwhile, dots per inch refers to actual physically printed ink. As you’ll see, dots per inch vs pixels per inch comes down to how the actual ink behaves during the print job.
Let’s consider printing a pixel with a color of pure cyan. Since Cyan is a primary channel in just about any commercial printer, its color can be produced rather simply. It is theoretically possible that one drop of printer ink could represent one pixel.
Compare this with a green pixel. This pixel color would necessitate a minimum of two printer drops – one from Cyan and one from Yellow. A color like dark orange could require Cyan, Yellow, Magenta, and Black. Not to mention dilute inks, if your printer has them.
But things get even more interesting as we refer to the density of the print job for high-resolution printing jobs. With fine art printers achieving printer droplets measured in the single digit picoliters, the color density can be exacerbated. It’s likely more than one droplet could be needed to produce one cyan pixel as well.
Print resolutions are commonly displayed as two numbers, such as “1440x720”. In this case, that would mean that the printer is putting down 1,440 dots horizontally, and 720 dots vertically. Sometimes, like with Epson print drivers on Macintosh systems, print resolution is displayed as one number, such as “1440”, which means 1440x1440.
Higher dots per inch mean more ink is consumed. If you are setting up custom print modes in RIP software, your ink over usage is at risk. The higher resolution you go, the more you will need to restrict ink limits to prevent over-inking artifacts.
However, if you are using a print driver, the manufacturer has already done this work for you. Because of this, you will not need to worry about over-inking. This is a major plus for those who are considering optimizing DPA vs PPI for printing.
For driver users, you will select a Media Type and then have limited selections for various DPI resolutions. These are typically under a section labeled “Quality”. The printer manufacturers give you options that are appropriate to the type of media you are printing on.
For example, a “Canvas” media type might top out at 1440x1440 DPI for printing. Meanwhile, a “Glossy Photo Paper” may go as high as 5760x1440 DPI for printing. The higher resolutions are not available on the “Canvas” media type. This is because that increase in detail would be lost in the texture of the canvas.
The options you are given in the driver should be approached as a trade-off between print quality and speed. Breathing Color recommends using the highest DPI option available in the Media Type recommended for our products. This is, of course, unless speed is a larger priority for your business. And just like PPI for printing, the best practice is always to test print and see what looks best to you and what works best for your shop.
Optimal DPI for Printing
Here are some general guides for the ideal DPI settings to achieve the best resolution for printing:
- 300 DPI – The image will generally look fine.
- 600 DPI – The image or graphics will look great.
- 1200 DPI – This is a high-quality density for a high-quality print job.
- 1440+ DPI – This will yield a professional-quality photographic print.
Conclusion – DPI vs. PPI
Do you feel like dots per inch vs pixels per inch is a little clearer now? Overall, they are not different names for the same thing.
The difference between PPI and DPI may feel like comparing apples and oranges. But both units of measure are critical in determining the ultimate quality of your final printed image. Optimizing your DPI or PPI shouldn’t be an either/or. It should be most closely related to what you’re hoping to achieve.
Just remember this: when considering the difference between PPI and DPI, it all comes down to different stages of the job. Consider your PPI during pre-production and consider your DPI when selecting the best resolution for printing.
Now that you understand DPI and PPI, you’ll be equipped to make the best possible prints for your needs.
