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).