What Resolution to Use for Scanning Artworks

A few days ago, I opened up one of my old scans on the Microsoft Surface Studio 2, an all-in-one computer with a 28-inch monitor that supports a resolution of 4,500 by 3,000. Looking at that 300dpi scan on such a high resolution screen made me wish that I had scanned at a much higher resolution. And that's where I got the idea for this article.

What resolution should you use to scan your artwork?

There's no one answer.

The resolution to use should be determined by where you want to reproduce the work. For example if you want to reproduce your art in a high quality print, you should scan at a resolution similar or higher than the printing resolution of the printer. And if you want to share your art online, you should note the width in pixel, and scan at a resolution similar or high enough to match that width.

Before we go further, let's define some terms first.

Display resolution: This is the number of distinct pixels that can be displayed on a computer screen in the horizontal and vertical axis. After you scan an artwork, it's going to be converted into a digital file with pixel dimensions.

Print resolution: This is the number of dots that can be printed in an area. This is usually measured by DPI.

DPI: Dots Per Inch is the number of dots that can be printed by a printer in a square inch. The higher the DPI, the more dots that can squeeze into a square inch, and the more details there will be.

PPI Pixels Per Inch is sort of like DPI but it measures the pixel density of a computer screen. The higher the PPO, the more pixels there are in a square inch on the screen, and the more details there will be. Remember the time when LCD monitors were still in its infancy stage and you could see the huge pixels that form the letters you read on screen? Those old monitors have low resolution and low PPI (pixel density). Fast forward to today, we have screens that insanely high resolution and pixel density that make pixels almost indiscernible by the naked eye. Some mobile phone screens have higher PPI than computer screens.

When we talk about scanning, we talk about the DPI we want to scan at. If we want more detail, we scan at a higher DPI. Once the art is scanned, we don't talk about the DPI anymore, we talk about the resolution, the actual pixel dimensions of the file. We only use DPI again when we want to convert the digital file to print.

If all these terminology is confusing for you, just remember that the resolution to use should be determined by where you want to reproduce the work.

Let's take a look at this pen and ink watercolour sketch. This file is 990 by 708. The artwork was scanned at a 600 DPI and the original resolution was 4,889 by 3,498. It was downsized to fit within the column width of my blog, 990px.

Scannning at 600 DPI to share your art online is an overkill. In this example, I could scan at 200 DPI and get a file that measures 1,630 by 1,166, which is still large enough for me to use on this page. If I were to scan at 100 DPI, the width would be 815 pixels and therefore not big enough fit the 990px column width.

Scanning at 200 DPI is usually enough for sharing artworks online. BUT if your original art is too small, then you have to increase the DPI to make the file bigger.

This file above is also 990 by 708, but it's a crop from a 200 DPI scan.

This is a 300 DPI scan.

This is 600 DPI. The higher the DPI, the more details you will be able to capture.

Scanning at this DPI took a longer time.

Scanning at 1200 DPI takes an even longer time.

At 2,400 DPI, you can see details you don't even expect. It looks like lines here are slightly less sharp compared to 1,200 and 600 DPI.

The maximum DPI my Canon LiDE 400 can scan at is 4,800 DPI. The scanning speed is excruciatingly slow. When I scanned the whole sketch, the scanning process just couldn't complete. Your computer has to have enough resources, memory, to complete the scan.

And if there's a mistake, it means having to repeat the tedious long scanning process again.

I did managed to scan at 4,800 DPI eventually, but I can only scan a section of my art.

I scan a square inch of my sketch. The file is 4,800 by 4,800 pixels. Then I reduced it to 990px wide to fit on this web page.

Scanning above 600 DPI feels excessive to me. A 600 DPI print will still look terrific. Scanning at even higher resolution is going to make your file size significantly larger, and will take up a lot of storage space.

These are the file sizes for the scan of my A5 sketch:

• 200 DPI - 4 MB
• 300 DPI - 9 MB
• 600 DPI - 33 MB
• 1,200 DPI - 119 MB
• 2,400 DPI - 315 MB
• 4,800 DPI - Couldn't complete the scan, but would probably be around 1GB

Conclusion

I used to scan my artworks at 300 DPI, but going forward I'm going to be using 600 DPI. The main reason is resolution for monitors and printers are getting higher. There may come a time in the future where you would want to print your work with a high resolution printer. A home printer like the Canon PIXMA Pro-100 that was released in 2012 can already print up to 2,400 DPI. So if your scan doesn't have enough resolution, it would mean you have to waste time to scan again, so why not scan it in higher resolution in the first place?