Photo Resolution 2018-03-04T21:15:23+00:00

Photo Resolution Computer & Printer Differences

How Computers Treat Image Resolution Differently Than Printers & How to Find The Resolution of a Digital Photo

This article discusses how to find the digital photo resolution value in dots-per-inch and clarifies how computer screens and printers view the resolution of a digital photo on your computer.

A good place to begin is to notice the simplest measurement for any photo whether it is digital or otherwise – the width times the height in inches. You should begin with this measure when considering the concept of resolution because if an image is physically small no other measure will make a lot of difference in your options for printing, enlarging, sharpening or displaying it.

Once you know the physical size of your photo, then it is useful to know other details about it. Digital images such as graphics on a web page or photos from a digital camera are all made up of pixels — “picture elements” — tiny units of picture information. Every image on your computer is represented by a colored grid of pixels.

Digital cameras record pixels, scanners convert images into pixels, photo-enlargement software like Imagener manipulates and adds pixels, a computer monitor displays pixels, and a printer prints pixels onto paper.

Computers use pixels to measure instead of inches. Printers use inches to measure instead of pixels. This is important because what you see on the screen can be very different than what prints out on your printer.

Pixels transform into inches through what is called “resolution,” — the number of pixels per square inch on a computer. The resolution allows you to transform pixels into inches and back again.

Two resolution definitions are often used in place of one another. Pixel resolution is the size (in bytes) of your image or its appearance on a computer screen. This number is tied directly to how big your image is on your hard drive. The byte size of the image file is directly proportional to the pixel count and its size on your computer screen, which simply displays all the pixels in a fixed one-to-one grid.

Embedded resolution is different. Embedded resolution tells your printer how far apart to spread the pixels in a printed image. It determines how “fine-grained” the printed image will look. It is completely independent of the pixel count (file size) of the image. A high-pixel-count image can have a low embedded resolution or vice versa. Given the same pixel count, a high embedded resolution will result in a smaller printed image (the pixels are packed together more tightly), and a low embedded resolution will result in a larger image (the pixels are more spread out).

230 DPI

230 DPI

600 DPI

600 DPI

For example, these two images are exactly the same size on your computer screen and they look the same, but they are very different. The first image has an embedded resolution of 230 dpi (dots-per-inch). The second has an embedded resolution of 600 dpi. Look at their appearance in a word processing program. The 600 DPI version will print out much smaller than the 230 DPI version which demonstrates how differently screens interpret lower and higher resolution images.

Kneson license plate showing how different dots per inch are interpreted in a Word processing program

You can try this for yourself with these two images. If viewing on a computer, right mouse click over each separate image above and save them to your hard drive – somewhere where you can find them easily. Now open a blank document in your word processor and load both images. You will see that the 230 DPI image is much smaller inside a word processor. This is because (most) word processors are showing you what the printer output would be (it is a “WYSIWYG” or what-you-see-is-what-you-get interface) and does not “communicate” in pixels but in displays the density of the 600 DPI image in inches.

Find The Resolution Value in Digital Photos

If you want to check the embedded resolution of an image, you can do this in the Windows Explorer. On a Windows computer, navigate to the image you want information on, right mouse click, click on Properties at the bottom, then click the Details tab. If there is an Advanced button on this next screen click it (depends on the version of Windows in which you are viewing the image). This will show the Width Height in pixels (see the red box in this image), plus the DPI resolution that is the embedded resolution your printer sees. If you perform this on the Kneson license plate images above, it will show you the exact same width and height dimensions but different DPI amounts. Remember that given the same width and height of two images, the one with more DPI will print smaller because the printer has to pack the same amount of image information into a smaller space since it is being told to fit more dots into each inch.

Image Properties Box

Image Properties Box

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