Snagging a Web Picture - how big will it print?

Snagging a Web Picture - how big can it be printed using a suitable resolution?

Let's say you are into vintage off-road motorcycling. You want a print of this web picture for your bulletin board, but you want good quality sharpness.

The picture above is 518 pixels wide x 800 pixels high. A sharp, quality print made on an Epson inkjet printer requires 200 pixels/inch or higher. In Photoshop (Image>Image size), you can keep the number of pixels constant and change the resolution to reach 200 pixels/inch (keeping Resample Image unchecked), but the print size will change. The resulting print size can also be calculated using the equations...

Solution

We know the number of pixels and the resolution needed. Calculate print size by dividing pixels by resolution.

Width = 518 pixels / 200 pixels/inch = 2.59 inches

Height = 800 pixels / 200 pixels/inch = 4 inches

While the sharpness of the print would be satisfactory at 200 pixels/inch, the print size (4" x 2.59") is small. It's only the size of a snapshot. Enlarging it further would reduce the resolution and perceived sharpness.

This example shows one of the disadvantages of using pictures found on the internet - they are usually too small to make large, high-quality prints.