Difference between dpi and ppi

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Difference between dpi and ppi

Post by webby » Tue Jun 26, 2007 4:07 pm

What is the difference between dpi and ppi? I am doing an ad layout, and the spec sheet calls for 300 dpi, but all I see in Photoshop is pixels/inch (ppi). Is this the same thing or am I missing something?

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Post by hal_nesbitt » Tue Jun 26, 2007 4:47 pm

Well, i'm surprised they are still using DPI - that is actually an old term that used to apply to everything from the resolution to the output. Specifically, DPI refers to a printer which uses 4 to 6 colors, depending on the printer. Since there is a small amount of colors, the printer will mix the ink to create the colors of the printout. This is done by creating a series of tiny dots for each pixel in the printout. Typically the higher the DPI, the higher the quality of the printout. So therefore if you are printing something that is 300 PPI on a 1200 DPI printer, then each pixel will be comprised of 16 little ink dots.

PPI is the preferred term when dealing with resolution and stands for pixels per inch. This is very specific, as it states exactly how many pixels are in each inch of the picture. If your spec sheet called for 300, then they are more than likely using DPI and PPI interchangedly. You can easily set the PPI in Photoshop by going to Image > Image Size and then entering the desired PPI in the resolution input box (pixels/inch). Remeber that 72 PPI is the standard for web graphics and 300 (or up) should usually be used for print jobs.
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