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Learn how to use the right DPI for Printing or On-Screen Graphics
danrichard.com — A detailed article that explains the difference between DPI levels for printing vs on-screen displays, and why the 72DPI rule is nothing but a myth turned pseudo industry standard. If you find selecting a DPI for printed applications confusing, this should clear it all up for even the greenest user.
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- adolfojp, on 10/12/2007, -0/+2This was a good article. I believe that some of the confusion behind DPI is Photoshop's fault. When you change the DPI setting in Photoshop (scaling), the "resample" box is checked by default. Uncheck the box and you will notice that DPI means nothing on the computer. Changing the DPI without resampling will not change the size of the picture, only the size of the print. The DPI info is embedded in the header of the picture, and minilabs will even ignore this number and rescale (change the DPI) on their own to fit the size that you asked for.
Quick math:
A 3 MP picture size is 2048 x 1536. Multiply those two numbers and you will get 3,145,728 pixels, or about 3 megapixels.
Divide 2048 pixels by 7 inches and you will get about 293 pixels/inch = 293 DPI. A perfect picture should be about 300 DPI on paper. Anything above 240 DPI will be fine for most people. A 3 megapixel camera will make near perfect 7 x 5 prints.
Quick conclusion:
Always take the size of your picture in pixels and divide by 300 DPI to check if your picture will look fine at a certain size on print. Don't bother in changing the DPI to take the picture to a minilap because it will ignore this info and scale as it sees fit. If they insist that you rescale your picture to a certain DPI make sure that you have your resample box unchecked or you will destroy your picture.- Sabin, on 10/12/2007, -0/+1Actually the rule for print is DPI = LPI * 2
So if your are printing a magazine and the screens are 200 lines per inch then you will want your images to be at 400 DPI. If you are producing an artbook and go for a 300 line screen then you will want 600 DPI images. The 300 DPI rule is a misconception that comes from the fact that the majority of magazines use either a 150 or 175 line screen when they go to print. - adolfojp, on 10/12/2007, -0/+1sabin - "The 300 DPI rule is a misconception that comes from the fact that the majority of magazines use either a 150 or 175 line screen when they go to print."
That is very interesting. Some friends of mine who work in an advertising company send their work to the printers at 300dpi, which is compatible with the 150x2 that you mention. You have spiked my curiosity and now I will give an hour to Google. :-) - Sabin, on 10/12/2007, -0/+1When i first got into print there was an excellent book that adobe sent us which is where i picked this up. Had TONS of great info to help you get the best looking print out of your files. Unfortunately we lost the book when my shop was renovated :(
- Sabin, on 10/12/2007, -0/+1Actually the rule for print is DPI = LPI * 2
- Faken, on 10/12/2007, -0/+1Actually, the last print ad I designed for the retail federation guide for the 2006 NRF required ads in 600DPI format... there's no written rule for it, you need to ask the publication or printer directly for the exact DPI level they want. The 300 DPI rule is a general rule of thumb for the average user to print out their own photos and have them in a quality worth adding to a photo album.
Dan
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