As a barcode supplier, we are often asked about DPM—what is it? Does it matter? On the other hand we find that there are some common misconceptions and assumptions regarding DPM we often have to explain.
So here we aim to explain what DPM is and the role it plays when it comes to barcodes specifically so you can more confidently invest in the best print strategy for your application. Let’s get to it!
What is Barcode Resolution/DPI?
When talking about barcode resolution, we’re talking about the same thing as print image resolution. Print image quality, or resolution, is measured in DPM or “dots per millimeter”—a literal description of the ink dots spread across the media depicting the final image.
While the dots may not be visible to the naked eye in most cases—they are there! In fact, they’re there before the image is even printed in a form you’re probably also familiar with—pixels. Pixels on a computer are very different from dots on a page, however they serve the same core purpose—spots that when viewed from a distance merge together to form a comprehensive image.
In a few words, barcode resolution is the overall quality of your barcode image measured in pixels per millimeter (PPM) on screen, and in DPM when printed onto your media—but what does that mean to you?
Does Barcode DPM Matter?
To a certain degree, the higher the DPM, the sharper the image and the lower the DPM the more likely it is to have a grainy appearance. This is because a higher resolution contains a higher density of dots. If you’ve ever grabbed an image from the internet and printed it only to find it didn’t look quite as you expected, you’ve already witnessed this first hand.
So yes, DPM does matter, and while the evidence so far points to high DPM being better—don’t rush out to buy the highest DPM printer you can find! A couple factors need to be taken into account when determining the best DPM range for your barcodes:
Barcodes are not Photographs
First of all, while barcodes are images often stored digitally as image files similar to photographs or graphics on your computer—jpg, png, img…etc.—they are very different from photos or digital drawings.
One of the biggest ways barcodes differ from a photograph or visually pleasing graphic is their purpose. Barcodes are a graphic representation of computer readable information—essentially a computer readable language.
This is a critical point to remember—barcodes are not intended to be interpreted by the human eye. This means that as long as your scanner can pick up the code and your computer can read it the barcode has served its purpose. Similar to handwriting—as long as it’s legible you understand the message.
Barcodes are also relatively simple in their structure—containing lines or blocks of black ink against a white background—in contrast to photos. Photographs require a range of gradation—and typically colour to accurately depict a subject. In order to create the necessary gradients and colours a high concentration of dots are required—and an even higher concentration is required to ensure a crisp image that is not only decipherable by human eyes, but appealing.
In short, barcodes generally don’t warrant the highest of DPM under the context of their purpose and complexity unlike printed graphics or photographs. However, that doesn’t mean barcodes never require high resolution—size plays a big role in your DPM needs.
For the most part you’ll find barcode printers with DPM capabilities of 8, 12 and 24 (though there are some 16 DPM printers around)—each of these will be best suited for different density needs.
8 DPM is best suited for less dense codes. Even with lower DPM the image can remain crisp and readable to the scanner. Medium to high density barcodes will perform much better at 12 DPM, and codes requiring especially high density will require at least 24 DPM.
Typically, lower density is best suited for larger barcodes and higher density is most suitable for smaller barcodes—especially smaller 2D barcodes—where sharp edges are critical in preventing misreads. But depending on what code you’re using, your needs may differ.
Also, keep in mind that you can print low density codes with a high density printer so you won’t need a different printer to meet all of your size and density needs. Utilizing a high DPM printer for low density printing can decrease the likelihood of misreads or no-reads by increasing the quality of those codes—where there was one dot with an 8 DPM printer, you now have 3 dots with a 24 DPM printer.
When to Invest in High DPM?
As we made clear in the last section, DPM does matter—but high DPM isn’t always the answer. There are three main circumstances where you might benefit from investing in a high resolution printer:
1. You are Required to by an Outside Party
Some industries—such as certain areas of the healthcare industry—may have standards in place specifying a minimum barcode DPM for use on important samples or documents.
There is a lot at stake when a sample is taken for testing—time and effort cannot be wasted when a patient is expecting a potentially life changing diagnosis. So, standards may be put in place to prevent potential liability issues or delays.
It’s also important to note that very small barcodes aren’t uncommon in healthcare—so these standards align with common practices.
2. Your Barcodes are Extremely Small
We’ve already touched on this, but particularly small barcodes—especially very small 2D barcodes—often perform best when printed at high resolution.
All barcodes perform best with sharp edges, but a sharp edge on a very small barcode isn’t achievable without high DPM. With the smallest of barcodes too much space between dots can lead to misreads or no-reads.
3. Your Needs Vary—or Might in the Future
Maybe you deal with multiple sizes of barcodes, or plan to accommodate smaller barcodes in the future. In this case, you’ll want to invest in a higher DPM model to ensure you can accommodate all of the size and density requirements you plan to utilise.
If you’re unsure and have the budget it may not be a terrible idea to go up a level to ensure your investment is sound even if future changes impact your barcodes. Typically, there won’t be an enormous difference in cost so in many cases it’s manageable to upgrade from 8 DPM to 12 DPM or 12 DPM to 24 DPM. You can expect to spend up to a few hundred pounds more if you choose to upgrade to the next resolution level.
Our main goal here, is to help our customers who may not be barcode experts better understand the role of barcode resolution and DPM so they—or you, can get the most value out of your printer purchase.
While it may not be far from the truth to say the higher the DPI the better—if 12 DPM works for your application, why spend more on a high-resolution printer you don’t gain value from? Or, on the other end of the spectrum, you end up losing money when you try to save by purchasing a printer that isn’t able to provide the resolution you really need.
As always, this is one reason we recommend working with a single supplier for your barcoding needs. With one supplier who is familiar with your needs and practices providing you with all the equipment you need to complete your barcode strategy, they can lead you in the right direction when it comes to the small but critical details like DPM.