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Getting a Digital Photo Ready for Print: dpi and ppi - Digital Photograpy

© Dan Osborn

What Pixels Per Inch (PPI) and Dots Per Inch (DPI) mean and how to work with them when preparing a digital photo for print.

There are a number of confusing issues surrounding the number of pixels it takes to produce a print from a digital camera. Solving this problem requires using complex multi-variable differential equations that can easily overwhelm even today's most powerful desktop PCs. And if you believe that then I have some beachfront property to sell you here in Arizona! It's really quite easy to figure out and there are a few simple guide lines that can help you get the Biggest Bang Per Pixel, or B2P2 - that's pronounced "Bee-two, Pee-two".

Just Print it Baby
The best way to figure out what your photo will look like when it is printed is to simply print it. Then, you'll know. Of course printing takes time and costs money. If you just bought that expensive photo paper then you'll want to make the best use of it and that ink ain't cheap either. So, experimentation is great but let's keep it to a minimum. If you make prints of your photos pretty often it will become second nature to you in no time. If you don't make prints very often then be sure to keep notes handy so that you don't make the same mistakes overr and overr.

Probably the single biggest point of confusion comes from Dot's per inch and Pixels per inch, that's DPI and PPI. DPI is the number of tiny little drops your printer can spray in a one inch square. When you're buying a printer this is a very important number to keep in mind. And, for a variety of reasons, it's also pretty worthless. That's because experts usually can't tell the difference between prints from a 1440 vs. 600 DPI printer. Companies measure their printer's capabilities differently because they use different technologies to print. 300 DPI is probably enough and 600 is plenty. This isn't like the processor wars between Intel and AMD. There is such a thing as enough. Instead of looking for huge DPI counts look for things like paper sizes the printer can accept, ink types/durability and cost per print. I'll talk about pixels for a bit and then come back and show you a test to tell you if your current printer is good enough for your needs.

Pixels, pixels everywhere
This is where things get tricky so I'm going to give you lots of examples and analogies along the way. Your digital images are made up of pixels. If you plan on printing your photos then you want as many pixels as you can get. Think of it like this: a digital photo is like a mosaic. The more tiles you have and the smaller they are the more realistic your mosaic will look. The tiles are like the pixels in your photo and the smaller they are is like the ppi - one more time for you acronym-a-phobics: that's Pixels Per Inch. The more pixels you have per inch the finer the detail will look. Think of ppi as pixel density. The more you pack in an inch the harder it is to tell the difference from one to another and that's what you want.