Dots per inch

Short for Dot Per Inch, DPI is a measurement of​ printer resolution indicating how many ink dots the printer can place in one square inch, the higher the DPI the sharper the image. Therefore, a printer that may have 600 DPI is a printer that can print 600 x 600 per square inch or 360,000 dots per square inch.

Because printers print using a series of dots, printers with a low DPI may encounter jaggies. Resolution Enhancement and other edge enhancements help correct the appearance of jaggies with printers that support this technology.

Newer LCD monitors have a slightly higher resolution.

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Why 72 DPI?

A long time ago a bunch of smart people decided that was a good size simply because it made text easy to read on the earliest MAC monitors.

In printing there are 72 points to a vertical inch.  What does that mean?  A font at a size of 72 will print up 1 inch tall, a font at the size of 36 will print up at 1/2 an inch tall.

Web pages, and images on the web, are measured in pixels, not real-world units such as inches.

DPI is printer specific...

Old dot matrix printers used about 36 dots per letter. The dots were physically big. 

Cheap inkjet printers have bigger dots.  You buy an inkjet printer for $400 your stuff is gonna look great- it has smaller dots.

My color lazer printer can handle up to 4800 DPI when printing--- I only use that for fun-- for everyday printing, even letters, 150 DPI still looks awfully darn good.  I leave the default value on my laser printer at 600DPI.


Smaller images contain less information...

You can only get so much information from an image file.  With JPG and PNG images the image size is often noted in PPI, not DPI.

An image that is 500 x 500 ppi has 25,000 bytes of info to work with.  You can take the width times the height of any image in pixels (ppi) to come up with an estimate. You can only stretch (or enlarge) that info so far before the image quality begins to suffer.

Think of that like a ball of pizza dough.  You can only make that ball of dough so big before it starts to tear in the middle.

If you tell your printer to print up that small image (the 500 x 500 one) at a resolution of 600 DPI, the image will get inversely smaller-- it only has so much information to work with.

Why 300 DPI?

The more DPI used for printing just means the image will look crisper.

Compare this to watching an old TV from the 70's (With a old school picture tube) and watching a HD flatscreen today--- stuff on the the flatscreen looks nice because the pixels are physically smaller, and there are more of them.

Once you start to get above 300DPI in printed material, the human eye really can't tell much about the difference anyway.

One big difference about 300dpi:  Straight lines, or curved lines at angles look much nicer at 300 DPI than 150.  At an output of 300 DPI straight lines, particularly those at 45 degree angles, and curved lines will have virtually no jagged edges.

This image is designed to be printed at 72 DPI and still look good...

Exported images from The Creator have a native output resolution of 72 DPI when printed.

If you take your logo to a commercial printer, and yes "Office Depot" is a commercial printer, they will say "It's only 72 DPI, we can't do it..."  You tell them to do it anyway.

I have taken countless sample exports to such places, and unless you are getting it enlarged bigger that a standard sheet of paper, you generally won't have any worries.

All of these images are designed to print up nicely at 72 DPI!

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