DPI (Dots per Inch) is the way professionals determine the clarity of a photo. It helps them know whether a photo is big enough to put on a poster, or if it can only really fit on a small card. If you’re printing photos or posting them on the Internet, knowing more about DPI is a sure-fire way to make sure your shots always look their best.
To make the term easiest to understand, you can think of it as “Pixels Per Inch” or literally how many pixels there are within each inch of your digital photo file.
You might also see the term PPI or “Points Per Inch,” but thankfully you can usually think of PPI the same as DPI.
The biggest mistake commonly made is trying to use DPI alone. DPI needs its constant companion: Inches!
For example: a photo that is 10 pixels square will be 10 DPI when you print it at 1 inch, but that SAME photo is only 5 DPI when printed at 2 inches. The amount of pixels doesn’t change, so when there are more inches, there are less pixels in each.
A 4” photo that is 300 DPI will work for a business card, but that photo is no good if you need to put it on a poster.
This is why you can’t ask someone for a file at a certain DPI without specifying inch size, and why you can’t give your printer a high DPI image and expect it to be good for everything. That number is meaningless until you attach an inch number to it.
Just remember: When looking at your photos, look at the pixel count not DPI, to determine how big it can be.
The MB Myth
Because DPI can be a complicated subject to understand, a lot of vendors will tell their clients to look at how many megabytes (MB) or kilobytes (KB) the file size is.
MB might be a quick way to see if a file has a lot of information in it, but it’s just not related enough to pixel size to be an accurate tool. A large file isn’t necessarily good to use and a small one isn’t necessarily bad. The method is just too imprecise to tell.
But here’s the kicker: it’s JUST as easy to check how many pixels your file has, as it is to check the MB size. Once you understand how to interpret the pixel size, it’s 100% accurate, much more useful, and super simple.
Skip the whole “MB” thing altogether, it’s not reliable.
You know that classic trope in a movie or TV show when the detectives are standing around a computer screen with a photo and someone says “Enhance!”? Forensic experts laugh at this fictional cliché. Unfortunately, your photos can’t be enhanced in real life.
Quality can be taken out of an image but never put back in.
A common rookie mistake is to take a small photo and blow it up, thinking that will make it better quality. However, all that does is make a big, blurry mess.
You cannot improve the quality of a photo by increasing its size. There’s only so much information there, and it’s impossible to create more information from nothing.
Increasing the size of an image is just using more pixels to represent the already existing number of pixels. So instead of 1 purple pixel you now have 4. Your image will still be blurry.
Fun fact, Google is working on technology to make “enhance” a reality. Google Brain makes a guess at what the image is based on its experience with similar images. Even though the information isn’t from the photo (it’s made up by the algorithm), the results look real. If we’re lucky, in the coming years this will be a tool we can use!
These are just general guidelines of course, examples for a rule-of-thumb. The exact pixel size needed will be determined by what type of project you’re working on. However, as you may already be able to tell, generally an image between 2000-5000 pixels will get you where you need to go.
If nothing else, this is the best rule to live by: always provide the largest image possible. When in doubt, larger is better, and any trained professional can take it from there.
Of course, a good design studio like yours truly will always be there to help you determine if your photo is big enough. Still have questions, or want us to take a look at your photo?