Thursday, November 25, 2010

New Year's Resolution

Understanding Image Resolution
 Let's start the new year with a good resolution. Ever wonder why the image you downloaded from the web looks all pixelated in print, but looked great on the web?

 Here's the short answer. Whatever we give the printer will determine the quality. Here's the explanation.
Images are made up of little "cubes" of colour named pixels. If you look at the illustration I provided, there are three different pixel counts displayed. These are all the exact same image. The 300 ppi (pixels per inch) is the original image resolution. I created the other two using Photoshop by reducing the pixel count.
 For good picture quality reproduction in printing, and to avoid the "staircasing" effect we require a minimum pixel count. This can vary depending on print process. For example, photographic prints will have reasonably good detail at 200 ppi, but 300 ppi will give you the best quality. Large format inkjet printers usually require a minimum of 75 ppi, however 100 ppi will produce a nice result. These resolution requirements need to be accurate at final reproduction size.
 For example, if a total image resolution is 2000 x 1000, divide by 100 = 20"x 10" to determine an inkjet reproduction size. Divide by 200, 10"x 5" would be a photo print size.
Some images that do not have enough resolution can potentially be used. There are programs available that "build" resolution into images, however capabilities are limited. Genuine Fractals is an excellent example and one of the better options - it works with machine language to construct resolution. Programs like Photoshop will interpolate image resolution, and are very limited in usefulness in this area.
 If you have any questions, feel free to email me at