Humans are incredibly curious creatures and we like to ask the big questions such as “How many licks does it take to get to the Tootsie Roll center of a Tootsie Pop?” The answer, of course, is not “one, two, three *crunch*…three!” but “Do not give nocturnal predatory birds your Tootsie Pop because a lot of them are jerks.”
We also like our quantifiable data such as how many miles there are to the sun or what’s the longest palindromic word? (93 million miles and saippuakivikauppias, a 19-letter Finnish word for a lye dealer.)
Another question that humans love to ask, at least to me, is “Okay, wise guy, if scanner resolution doesn’t equal quality, how much is enough?” It’s a fair question because scanners, especially photo models, tout all kinds of really high resolution specifications. What are those 4800 and 6400 dpi ratings for?
The answer is enlargement, to embiggen, if you will.
The standard for a 1:1 image size from a scanner is generally 300 dpi. This is based on how well a typical human eye can resolve images made up of pixels (dots) at typical viewing distances of about 12”. In old printing technologies that used dot patterns lower than 150 dpi, like Golden Age comic books, the dots were very visible at normal viewing distances and it looked as if Superman’s face was covered with Kyrptonian super measles.
Given this information, if you are scanning prints or documents and want them to be reproduced at the same size, 300 dpi will give you enough pixels. Given that baseline, you can do some basic math to determine how much resolution you need for making enlargements. If you wanted to create an 8” x 10” print from a 4” x 6” original, divide the two short sides (8 ÷ 4 = 2), then multiply that by the 300 dpi base (2 x 300 = 600). The 600 dpi scan will give you enough pixels to resize up to 8” x 12” and with a little cropping (you didn’t want Uncle Schmendrick in that photo anyway) you have your 8” x 10”.
The big resolution numbers come into play when you’re scanning something very small, like a 35mm slide. If you wanted to create a 16” x 20” print from a slide (1.29” x 0.8” roughly), you can run through the formula of dividing the shorts sides (16 ÷ 0.8 = 20) and then multiplying that by 300 (20 x 300 = 6000) meaning you’d need one of our 6400 dpi models to get that big print from your slide.
Just like almost everything you learned in math class, now that you understand what the resolution numbers mean, you can let a machine do all of the actual work. In the Professional mode of your Epson scanner driver, you can leave the output resolution at 300 dpi and use the pull down menu to choose an output resolution. The driver scales the resolution accordingly and even provides a crop frame so you can see how best to crop out Uncle Schmendrick.
So in conclusion, that’s how your scanner’s resolution works. Don’t give owls candy unless you want your heart broken and please send me the contact for a good saippuakivikauppias, I’m almost out of lye.