Best resolution for large format output and viewing distance

This is a question we get asked almost on a daily basis: How big of a print can I make with an image that was taken by an 8, 10, or 12-megapixel camera? The answer is twofold. Yes, there are limitations of each camera and the maximum file it will produce, in turn limiting the size enlargement you can produce without showing any file loss. However, the other factor to consider is the viewing distance of your print.

The human eye has a good, but limited perception of resolution. This means that beyond a certain level of detail there is nothing much to be gained by ever higher resolution images. The trade-off that occurs depends on how far your eyes are away from the print. Did you know that the average billboard print is produced at 2 to 20 dots per inch? For that format, the lower resolution is acceptable because the print is viewed from yards away, and your eye fills in the detail.

Of course, much of this has to do with the expectations you have for your print. If you do not want to see any file loss or pixelation in the print, even when viewed up close, it is best to try to stay above 125 DPI at your final output size. For a quick reference, take a look at the chart below.

If necessary you can push your file larger than those restrictions, often with amazing results. Typical areas that will show file loss first are large areas of one color or gradients, like a sky. The gradient may not transition smoothly and start to band, or you may see pixel noise in parts of the sky. Other things to keep an eye out for are halos. Those can usually be seen in places where the detail of an image meets a large area of gradient, like the horizon line of a landscape image. Most of these can be caught on screen. Remember to zoom in and view your image close to look for any artifacts. If you can see it on screen, you will see it on the print.

There are also several software applications available that can optimize your file for output, like Genuine Fractals. The thing to remember when using software like this is that it will not fill in the detail of your image. What it does do an amazing job at is making the transition from a small to a large image smoother. Instead of the jagged pixel lines left over from an overly stretched file, it will fill in the dots so to speak, and keep the lines more even.

Print size, file resolution, and viewing distance work hand in hand with digital printing. One ultimately affects the other. Remember to consider where and how the print is going to be used when you determine the size you would like printed.