Well, yes and no.
“Why can’t I use certain pictures? They look great on my phone and my computer.”
I’m quite sure your pictures do look great, on your device, but printing them is an entirely different matter. Images prepared for digital uses, such as emailing, texting, or placing on websites, are not high enough in quality to use for printing—their purpose is to load as quickly as possible.
When these images are placed in printed materials, the crisp sharpness and fine details suffer; those digital images can make your stunning printed piece look disappointing.
Yes, you can alter the images, but you can only do so much with the one you start with.
It starts with DPI!
One very important, often overlooked detail, is the “Dots Per Inch”, DPI valuation.
This measurement gives us the number of ink droplets a printer can place in a single inch of printed space; the higher the number, the sharper the printed details.
The standard DPI for printed materials is 300, with some professional printing services printing at 600 DPI or higher. In comparison, digital images have a standard of 96 and often even as low as 72!
DPI is also used to calculate how large a digital image will be when the image is physically printed. The real resolution of a digital image is based on its pixel measurements, for example, 1920 × 1080 pixels.
“What? How confusing!”
Let’s dive a little deeper.
What is a pixel?
A pixel is the smallest unit of one color in a digital image. Placed next to each other, they create intensity and detail for the viewer.
To understand this, let’s look at the age-old industry of printing newspaper images. They use a method called half-toning, using different sizes of ink dots along with varying spacing to create depth, called stippling. Larger dots create darker shades, and smaller dots create lighter shades.
Think of each dot, or pixel, as a single brick in a brick wall, imagine it’s red. From afar, it’s just a red brick wall, but up close, each brick has its own unique shade of red with slightly different textures. As you look even closer, you can see the variable sizes and hues of each grain in the material of every brick.
How does this tie in with the quality of a photo? The size of the pixels is an important factor in the DPI resolution of an image.
How do I find the DPI resolution of an image?
That depends on which type of operating system you are using. Below are simple steps to assist you in finding those baffling properties.
Windows-based Computer:
Using the File Explorer
1. Open the File Explorer.
2. Right-click on the chosen photo file.
3. Select Properties.
4. Go to the Details tab.
5. To find the DPI resolution, look for fields labeled Horizontal and Vertical resolution
Using the Paint app:
1. Open the Paint app.
2. Open your selected photo.
3. Click on the File tab.
4. Select Image Properties and view the resolution settings.
iMac:
Using the Finder
1. Right-Click in the image file.
2. Select Get Info.
3. Open the drop-down arrow of More Info.
4. View the Dimensions listed in pixels.
Using Preview App
1. Open image in Preview app.
2. Go to the Tools tab.
3. Select Show Inspector.
4. View the Image Size and Image DPI.
Android devices:
1. Open your Gallery or the photo library you are using.
2. Select your photo.
3. Click on the three-dot ellipsis.
4. Click on About, the lowercase “I” in a circle.
5. You will see something like “12 MP” and “3024 x 4032”.
Apple devices:
1. Open your Photos app.
2. Select your photo.
3. Tap on the Information icon (lowercase “i” in a circle).
4. You will see a box with something like “12 MP” and “3024 x 4032”.
MP is megapixels, which shows the total pixel count of the image. The dimensions show the width and height in pixels.
This is where a simple formula comes in handy. To calculate the print size of an image, take the image width and divide it by the print width. For example, if an image is 600 pixels wide by 900 pixels high and you want a print size of 2” x 3”, take 600 pixels [divided by] 2 inches = 300 DPI. Similarly, take 900 pixels [divided by] 3 inches = 300 DPI.
Which Image Dimensions Are Ideal for 300 DPI Prints?
For a 300 DPI print, you must consider the document’s size and resolution. As an example, a 4” x 6” print needs a digital image that is 1200 x 1800 pixels.
Considering the common dimensions of 8.5” x 5.5” for postcards mailed through the United States Postal Service, the frequent size for a personal headshot is approximately 2” x 3”. We want your piece to look terrific, so the minimum picture dimensions should be 600 x 900 pixels.
Last but not least, let’s discuss file types.
There are several file extensions or types that affect the quality of printed materials.
One commonly used file type is a JPG, or JPEG. This file with the extension would be MyImage.jpg or MyImage.jpeg. A jpg has been, for quite some time, the easiest type of picture file to work with. It is compressed at different levels, which affects the size, making it perfect for digital use. Unfortunately, a highly compressed JPG file also has what the creative fields call “noise”.
We don’t need to go into that, other than knowing that a lot of “noise” can be seen by the human eye.
Another fairly common file type is the HEIC. Although HEIC files are not completely exclusive to Apple devices, Apple was the first major adopter of this file extension. These files can easily be converted to JPG or PNG files with the right software.
Numerous other file formats exist, although they are mostly used in professional fields such as photography, designing, archival, medical, and more. Unless you would like to expand your cyber-skills, it’s not necessary to understand the differences between them.
Enter the PNG! This fun file type is versatile and allows the creation of transparent backgrounds. It’s easy to convert and does not have the compression that JPG files do. The plus side of that is NO NOISE, (well, OK, less noise) with increased sharpness and a great display of color. It is no wonder that this is the preferred file type of printing professionals.
To summarize it all in one sentence!
That’s a lot of information to absorb, I know, and it can feel overwhelming at first. To make things clearer and easier to understand, let us break it down and summarize everything into one simple, straightforward sentence.
“For the best printing results of your photos for mailing pieces, the image would optimally be a PNG at 300 DPI, no less than 600 x 900 pixels.”
Do you want more information about our postcard mailing options? Follow this link to fill out our easy form.
Sources:
Adobe, Photography, “DPI Resolution: Your Complete Guide”, https://www.adobe.com/uk/creativecloud/photography/discover/dots-per-inch-dpi-resolution.html, accessed 17 November 2025
Stack Exchange, Photography Questions, “What is the stippling effect used in newspapers and comics called?” April 2017, https://photo.stackexchange.com/questions/88867/what-is-the-stippling-effect-used-in-newsprint-and-comics-called-and-how-can-i, accessed 17 November 2025
Poster Print Shop, “Checking Your Photo’s Resolution: Tips and Tools”, https://posterprintshop.com/guide/how-to-check-resolution-of-a-photo/?srsltid=AfmBOoo0U_vQOGPk-rP4DenY4yLSeL9DoUg6O2NKpDeRBoD7174L146-, accessed 19 November 2025
Images provided by Adobe Stock Photos and TargetLeads Creative team.