I disagree Silvertongue62. Forcing your images to 300ppi for digital applications is a really bad idea. Here's why.
No computer screens (at least very few available to any consumer) can display a 300ppi image and will instead display all the image pixels at their native resolution of 72-100ppi. The resulting image will be approximately 3 times the pixel dimensions when displayed outside of Photoshop. In almost all cases the end use for the image is much smaller than the that 300ppi original forcing the display program (Flash, web page, etc) to resize the image. This process alone causes two problems.
First 3x the pixel data means approximately 3x the size. If you resize an image in Flash for example it KEEPS all the extra data but doesn't actually display it meaning that your eating up lots of bandwidth you wouldn't need.
Second I've never seen a program that could resize an image to anything other than quarter increments without causing lots of image degradation meaning that even though you have all the pixel data the image quality will actually decrease. For example if I resize an image to 50% or 25% its original size it will look ok, but as soon as I resize it to 73% it will start to look fuzzy. There's a really good chance that the final required size won't be one of those quarter increments meaning the image will not be what it should.
Instead you should ALWAYS work at the native size of your end product. So in Photoshop if your end goal is a website to display on a computer screen you should be working at 72ppi so that your project pixel dimensions match the final output. Meaning you want your image that's 400px wide to take up 400px on the site instead of approx 1200px.
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