Print Quality: What is DPI?

DPI has been mentioned in tens of our blog posts. I've nearly always highlighted it so you can click to see what the letters stand for. But telling you what the letters stand for is one thing, now it's time to tell you what DPI means.

Pre-Print vs. Post-Print

Before we get onto the main subject, I want to first talk about the print quality from software to printer. Thermal transfer and direct thermal printers can't intentionally produce half colours. What I mean by this is if the ribbon is black and the label is white, the printer can't produce grey. Let's look at some examples. Here I've typed DPI in a curvy font. In each of the examples, I've highlighted an area of the letter P, which we'll look closely at. The zoomed section is to the right of the letters. In the software, everything looks okay on the screen. We zoom in and we can see greys and other colours filling in the edges to make the black arc look as smooth as possible at its original size.

Now let's look at how it will look after printing it. The letters look fine, it's readable, but the edges are not as smooth as they were in the software. When we zoom in we can see all the pixels that were not black have been converted to either white or black depending which they would be nearest to.

DPI: 200 vs. 300

Let's imagine I've just printed this out of a 200 DPI printer. The letters "DPI" are around 6mm tall. That doesn't sound very big, but by comparison letters in a newspaper paragraph are around 2-3mm tall. It's very stuttered around the edges but if you are printing larger text, it probably doesn't matter.

Same again but through a 300 DPI printer. The gaps from the previous sample have been smoothed out. It's still ~6mm tall.

What to buy?

The majority of the printers on the market are 180 to 200 DPI. Some printers such as the LabelStation Pro300 and the Dymo XTL range are 300 DPI which allows you to print detailed, intricate label designs with small fonts, small barcodes and detailed graphics. If you're having trouble deciding on the perfect printer for your requirements, call our knowledgeable sales team on 01202 681311.