Resolution Redux

© Black Rhino Illustration

The bridge between technician and civilian is vast in any field of knowledge. No less so than digital photo reproduction…uh, I mean scanning.

You might know by now that my favorite image scanner brand is Epson (for now). Currently, their "Perfection" models are the perfect entry- and mid-level scanner to get prints, negatives, slides and documents into a digital form (documents are really an entirely different animal that can get by better or same with HP or other brands).

When shopping for a scanner, the most common and basic facts you want to know about is its resolution. Resolution is essentially the muscle of a digital image. Low resolution gives low results; poor detail and usability. High resolution is where a big part of quality is found.

Epson Perfection V500

Looking at the Epson Perfection series specifications (comparison shop Epson here), you'll find at least 2 types of resolution: Optical Resolution and Interpolated Resolution. A scanner's "real" resolution is going to be found under the Optical specification. Interpolated is just how much the scanner can fake or force higher resolution—the concepts of which I explain and demonstrate in the Photo Restoration Basics course (shameless plug, I know!).

For demonstration purposes, let's take the Epson Perfection V500. This has an Optical Resolution of 6400 dpi (should read ppi, but that's another argument for another day). This sounds huge, right? Well, it is—relatively speaking. First, you must divide that number of 6400 by four—or whatever number you find listed for Optical Resolution. In that case, the sum is 1600.

So this particular scanner will create a digital image at 100% size in 1,600 pixels per inch/dots per inch. That is what I consider excellent resolution. So if I have an 8x10 print, it can be digitized as large as 1,600 ppi/dpi at 8x10 or 300 ppi/dpi at 42x53 inches (108x135 cm)!

Resolution is always treated as an "easy" topic not worth discussing for most teachers. But I like the basics. I hope you found this useful. If so, post a comment, share it and/or subscribe to the Photo Grafix email newsletter.

—Eric C. M. Basir