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Tuesday, May 19, 2009

Printing: Back to Basics

If you're creating artwork for print, you'll only get decent results if you've got a basic understanding of image resolution. Don't worry, it's actually quite a simple concept - nowhere near as complex as some people seem to think. So stick with me here, I'm going to try to make this as painless as possible...


Resolution is a concept that continues to baffle even graphic artists. In the context of editing photos, resolution is a measurement of the output quality of an image. The most common units to measure resolution include: PPI (pixels per inch), DPI (dots per inch), LPI (lines per inch), and SPI (samples per inch). For our purposes, we will focus on DPI and PPI because that is what you will be dealing with most often when printing photographs.

As you probably know, when you view a photograph on your computer monitor you're actually looking at a grid of tiny dots or 'pixels'. Similarly, when a photograph is reproduced in print, it is made up of thousands of small dots of ink. Resolution refers to the number of these dots (or pixels) which are squeezed into a given area. The smaller the dot, the more dots you can fit into a horizontal inch, and the sharper an image will appear to the human eye (up to a point).
If you zoom into a photograph on your PC monitor you will be able to see the grid of pixels which make up the image.

The resolution of an image is usually measured in dots per inch (dpi) or pixels per inch (ppi). Essentially dpi and ppi refer to the same thing, it's simply the number of dots or pixels which make up an image. For more information on pixels see my earlier post Vector -VS- Bitmap: A basic breakdown.

If you view an image on your computer monitor its resolution will need to be at least 72dpi to appear sharp and clear. A lower resolution will result in large pixels which will be detected by your eye, resulting in a fuzzy or 'pixelated' image. However, if the same image were reproduced on paper using a commercial printing process it would need a resolution of around 300dpi to achieve a sharp result.

A printed image requires a much higher resolution than an on-screen image (4 times greater to be precise). Therefore, just because your image looks sharp and crisp when viewed on-screen, it doesn't mean it will reproduce correctly when printed.

Tune in Friday for how to improve the resolution of an image for printing!

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