I'm used to thinking of hi-res 300 ppi and above, and lo-res, 72 or 96. But today I got an image that was 240 ppi, and da boss wanted as high res as possible. It was a huge file, but when I resized down to 700px wide in PS, optimized jpeg with no compression, without changing the res the result was a 129KB file that looks decent on most browsers (at least my box...who knows about old monitors, etc.) Did I miss a conference when I was on a break? Are others doing medium-res?
The size at which an image appears on your screen depends only on two things – the pixel dimensions of the image and the display resolution of your screen. As long as you’ve set your screen to its native display resolution...then an image will be displayed pixel-for-pixel. In other words, each pixel in the image will take up exactly one pixel on your screen. For example, a 640×480 pixel image would fill a 640×480 pixel area of your screen. An 800 pixel-wide banner on a website would appear 800 pixels wide on the screen. No more, no less. And no matter what you set the image’s resolution to in Photoshop, whether it’s 72 ppi, 300 ppi or 3000 ppi, it will have no effect at all on how large or small the image appears on the screen.
That’s because image resolution affects only one thing – the size of the image when it’s printed. By setting the resolution in Photoshop, we tell the printer, not the screen, how many of the pixels in the image to squeeze into an inch of paper. The more pixels you’re squeezing into every inch of paper, the smaller the image will appear when printed.
So if you set your images to 200 ppi, they will just print much smaller than they appear on the screen.