Quote - You have a printer, whose resolution is fixed at, say, 72 dots per inch (DPI), a dot being the smallest paper space that it can fill with its ink or toner. Then you have an image set up to 300 DPI, fine. Do you think your printer would produce a 300 DPI image? I don't think so :) DPI is significant if, and ONLY if, you are setting your RENDERED image to be X inches to Y inches WHEN PRINTED; really, it's only an helper to find the correct render dimensions in pixels for the desired print dimensions in inches. If you have Photoshop (or even GIMP, the idea is the same) you can test this: - set units to inches, then set up a new image 5x5 inches with a 300 DPI resolutions, then switch units to pixels and note the dimensions of the image. - do the same, but now set your resolution to 150 DPI, and note the new numbers after switching to pixels again: do they are exactly half of the previous ones? One pixel on the video screen corresponds to one dot of the printer device, and while screens have about 72 pixels for every inch, printers can have (and DO have) much higher resolutions, up to 4000 and more dots per inches in professional (and costly) devices. When you are watching a 10x10 inches image on your screen, you are really seeing a 1072=720 pixels image; to print this 10x10 inches image on a 300 DPI device, you must have a dimension in pixel of 10300=3000. You can set it directly, but the inches+DPI units can help you to find the correct dimensions in two easy steps, if you want. I said: INCHES+DPI...if you are working with pixels as units, DPI is only a screen filler :D

 

I entirely agree. But if you look back the original question wasn't printing related. The actual question was:

"There something that bothers me for a long time: Can someone explain that dpi is so important for rendering? !

As regards rendered images, you do get more detail per square inch with Higher DPI settings in your "Render Dimensions" window, providing the Max.Texture setting in "Render Settings is suitably high.

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