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Hello,

I found this website while doing a Google search for "internet 72 dpi", trying to help a friend get a better understanding of dpi and it's affect (or lack thereof) on images. I was directed to the following page:

http://www.scrapgirl...lution_size.htm

There is some information in this tutorial that isn't quite right, and I thought I would help straighten out the issue.

The first and most important point is, DPI has no affect on digital images. The internet is not 72 DPI; it is in fact no DPI at all. There are no inches on the internet. Saving a file at 72 DPI for displaying on the web is a meaningless exercise. You could save the same files at 1 DPI or 9,000 DPI and it would look exactly the same. The only thing that matters with digital files is pixels. The DPI setting on a digital file is just a bit of metadata that says "If I were to print this image on paper, please print the pixels at the following density". Also, the file size of web images is not affected by DPI. Try it yourself; change the DPI setting to 1 and 300 and save it both times. The file sizes will be the same.

The tutorial says "Because 72-dpi graphics have fewer dots...". This isn't true. The number of dots in your photo has nothing to do with it's DPI setting. The DPI is simply there to tell the printer how many of the images' dots to print in a given square inch of paper, should you send the file to the printer. Therefore changing DPI will change the size of the photo when it is printed. It will not change anything else, and is completely ignored by web browsers. Also, 72 DPI images do not have "larger dots" than 300 DPI images. A pixel is a pixel; it's size never changes. Dots do not get larger or smaller; only the density of them changes (how many dots are squeezed onto an inch of paper).

Hope this helps clear some of that up. One other somewhat useful fact: while 300 DPI has been the industry standard for printing digital files and is a fine setting, if you're trying to print big enlargements you can usually get away with much smaller DPI numbers. I can't tell the difference between a 300 DPI print and a 240 DPI print, and I've even printed photos at 140 DPI with acceptable results. Not recommended, but you can often get away with it if you must.

Derek