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The Photoshop Phanatic: Photoshop BasicsPart 1: Resolution
In this introductory column of Photoshop Basics, we are going to define the concept of resolution and try to put to the bed the myths about which resolution is best for each situation.
There are many terms thrown around when discussing resolution--dpi, ppi, and lpi. First, let's shed a little light on what these acronyms actually mean.
How do these measurements relate to one another?
You have acquired an image, now what?
Determining what resolution to use depends on what your output will be, but it is always better to start with a higher resolution scan and then sample down to the output size you need. Use the following as a guideline:
For any screen-related medium the image should be low resolution.
If your final output device is a computer screen, it's better to start with a higher resolution scan (say 150 ppi) and then edit the final image down to 72 ppi or 96 ppi. For example, PowerPoint onscreen shows should be 72 dpi or 96 dpi depending upon platform playback.
You are probably wondering why either 72 ppi or 96 ppi? Well, the 2 major computer operating systems (Macintosh and Windows) measure screen resolution differently. The Macintosh operating system assumes a default screen resolution of 72 ppi while Windows assumes 96 ppi.
Last, but not least, I would be remiss if I didn't mention the other screen medium--television. Now you may wonder why you would ever need to output anything to a TV? Well you never know, so why not be prepared anyway? Television is a low resolution format. Here in the US we use the NTSC format. Television's default resolution is 640 pixels by 480 pixels at 72 dpi or, if outputting to television in Europe (the PAL format), the default resolution is 720 by 576.
For images that will be printed on paper use higher resolution (in the range of 150 to 300 dpi).
Hopefully this has cleared up any resolution dilemmas you have. Until next time, Happy Photoshopping!