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05/30/2003: "Image Resolution"

Digital cameras are everywhere, and with four plus megapixel cameras, priced for the consumer market, a lot of people out there are learning to do image editing for digital presentation and wondering what these huge images are all about. In a nutshell, these huge images are about detail. They are about the kind of detail that produces a printed image approaching film print quality. To understand these huge image resolutions the operative word to consider is "printed" image and, therefore, print resolution. Digital presentation of images, on the other hand, is concerned with display resolution. Display resolution, or size expressed as pixel dimensions, is entirely different than print resolution. Click more.. below for the lowdown.

Display resolution means how your image looks on the computer screen. If your monitor is set to a resolution of 800 by 600 the screen is formatted 800 pixels wide and 600 pixels high and if an image, or picture, is sized at 400 pixels wide and 300 pixels high it's resolution is 400 by 300 and it will fill exactly half the screen if used as wallpaper on that screen or when placed on a web page and viewed through a browser on that screen. Display resolution is the only thing that counts in digital presentation of images.

Print resolution, on the other hand, is concerned with the defining the desired size of the printed image and the number of dots per inch that the printer will print to reproduce the image. Display resolution, or size expressed as pixel dimensions, comes into play here only when computing the maximum number of dots per inch that are available to the printer at one pixel per dot. What it comes down to is that the greater the number of pixels available to produce a given size of printed image the greater the number of dots per inch, at one pixel per dot, the printer can use to define the detail within that image.

This is not rocket science, an image is so many pixels wide and so many pixels high and a computer monitor is, likewise, so many pixels wide and so many pixels high. The percentage of the screen that a given image will cover depends on the resolution that the monitor is set to. A given image will cover more of a screen set to 640 by 480 resolution than a screen set to 1024 by 768 resolution. Similarly, in a printer scenario, the larger the size of the desired print the more pixels are required, at one pixel per dot, to produce a high level of detail, say 800 dots per inch. This means an 8 by 10 inch print of a given image will contain less detail than a 5 by 7 inch print of the same image.

I think a lot of the confusion about image resolution is based on a "what you see is what you get" expectation without regard for the type of application being used to view or manipulate the images. When working with images keep in mind whether the intent of the application you're using is to show you how your printed output will look or how your image will look on screen or in a browser.

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Replies: 3 Comments

So, the whole thing revolves around printed display versus monitor display. How interesting.

a confused person said @ 06/09/2003 08:41 AM CST

No. None whatsoever.

Cliff said @ 06/02/2003 03:31 PM CST

Thank you! You have cleared up a lot of confusion for me. Does the print resolution showing in the Photoshop Image Resize dialog box have any effect on the Save for Web process like how many KB the image turns out to be?

Enlightened said @ 06/02/2003 01:35 PM CST