What resolution do I publish for projection or print?

I often get asked the question – what resolution or dpi  (dots per inch) should I be setting my PhotoWorks rendered output to?
This is a question that you should have an answer for because it could cost you unnecessary time if you render at too high a resolution, but also cost you having to redo your rendering when discovering that the final output is too low when printed.

This is actually a generic question and applies to any type of media that you’ve created on your computer, not just PhotoWorks. Then having to make this decision, the first question to ask yourself is: what is the target application? In other words, are you going to be showing your image in PowerPoint, on a DVD, or printing to a color inkjet printer. Often, the biggest distinction is between computer projection and printed material.

First, computer monitors (or projection displays) only have an effective resolution of  between 72 ppi (pixels per inch) to 120ppi depending on the size and quality of the display. Some of the new flat panel displays can achieve 120 ppi.  Contrast this with inkjet and laserjet printers which are capable of printing the equivalent 250 dpi (dots per inch) on paper medium. Although dpi and ppi do no necessary correlate, the general rule is that if you need to print your rendering or visual presentation, you’ll need approximately 3 times the resolution than if you were to project it.

Here’s my general rule-of-thumb that’s worked well for me and everyone I’ve instructed: A) if you are going to present on a computer, use 100 ppi; making your rendering or document any larger is just a waste of your’s and your computer’s time (rendering.) The exception to this is if you are going to zoom in on the original image of course. B) If your target is a letter size piece of paper, make your resolution no smaller than 250 dpi and no higher than 300 dpi (if you can afford to.) Remember that final output size and resolution are proportional. That a fancy way of saying that the bigger the piece of paper, the high the resolution must be. Total image size of 200 dpi on a 8.5 by 11 sheet of paper is not the same as the same 200 dpi on a 30×40 poster. That’s because the total 850 pixels of information spread out over 30 inches verses 8.5 inches is quite different. To be the equivalent resolution on a 30×40 poster the resolution must be 30/8.5= 3.5 x 8.5 x 200 = 700dpi. This is why most digital cameras can still not match film photography cameras for doing large printed reproductions. Inversely, if you are printing wallet size photos you can go to lower resolutions. So just keep this ratio in mind when going larger or smaller.

Going to 8.5 x11 print = 250dpi
Going to computer projection = 100dp

Fielder