Rachel’s Five Rules of Scanning

After I wrote my tutorial on how to clean up line-work, it occurred to me that I should talk a little about scanning. I didn’t have space to do it in the linework tutorial, but I do have a few thoughts on scanning. Here’s some advice from someone who scans a lot both for my hobbies and for my job where I usually am the one digitizing historical materials.

Scan in High Resolution.

When I was first learning how to cut wood, I was taught- You can make a piece of wood shorter, but you can’t make it longer. In other words, cut a little bigger if you have to choose. Since slicing off an inch is easier than realizing you’re short an inch.

You can always reduce the resolution of an image, but increasing it will result in loss of clarity.

Resolution is something people seem to get confused about, so let me try to explain. Resolution is always measured by the number of dots per one linear inch (in the US, other places use the centimeter). This is shortened to DPI (Dots Per Inch) for as most printers or Pixels Per Inch (PPI) for digital media.

No matter how high PPI (Pixels Per Inch) your image is, the internet has a resolution of 72 PPI. Meaning, if you create an image that is 200 PPI and measures two inches tall, when you post it on the internet it will appear to be 5.5 inches tall. ((22 PPI * 2)/72PPI = 5.5)

Some professionals work as high as 1200 DPI, but I think that’s a bit much. Bare in mind that professional publications are usually printed between 300 and 400 dpi.

Choose your File Format Carefully.

There are many digital file types. I’m going to talk about a few common ones here.

“JPEG” stands for Joint Photographic Experts Group- a fact mostly useful to show off your knowledge, but won’t really matter much. It is sometimes also called a .jpg or a jpeg. JPEGs are always compressed files. JPEG is designed for compressing either full-color (24 bit) or grey-scale digital images of complicated real world images (photographs). It is a great format when there is subtle color change in an image, but using a high compression rate can result in loss of quality.

“GIF” stands for Graphics Interface Format. It is an 8 bit format meaning that maximum number of colors supported is 256. GIFs are always compressed and rarely used these days.

“PNG” stands for Portable Network Graphics format. This was an updated version of the “GIF” format and literally supports millions of colors. It is the format I usually use for my web posts as it tends to compress to a small size without loss of detail and my paper dolls are full color without a lot of subtle shades. PNG has largely replaced GIF on the internet.

“TIFF” stands for Tagged Image File Format. TIFF was originally designed for scanners as a universally acceptable format in a time when scanning companies all had different formats they were using. TIFF images are not compressed as a default setting. This is the preferred format for archival scanning, because there is no compression. However, the lack of compression results in very large sized files. Therefore, TIFF files are rarely posted or shared on the internet or printed from. TIFF files can handle bi-level (black and white), grayscale, palette-color and RGB full-color images.

When I scan, I scan at 600 dpi as an uncompressed TIFF files in greyscale, since I work in black and white.

Save your raw files.

I call my rough scans “raw files”. Theses are my 600dpi uncompressed TIFF files, usually in greyscale. They are very large files.

I keep them in a folder called “Raw Files” it contains all the raw scans dating back a long long way. Sometimes, you have to go back to the very beginning, so keep a copy of the unaltered scan in case you need it.

Hopefully you won’t, but if you do than you’ve got it. I have only had to go back to these files once or twice over the years, but I have been grateful I had them if I needed them. (Usually, because I accidentally deleted something.)

Know you Scanner and Choose it Well.

I have used HP scanners, Epson scanners and Canon scanners. They are all a little different. Learn your scanner settings. Read the manual. Get comfortable using it.

If you are scanning full color art work, than carefully check how many colors the scanner can read. A colored pencil drawing, for example, can literally have millions of subtle shades. If your scans are coming out poorly, than is it your scanner? Your scan settings? Or can your scanner just not handle the color depth.

I don’t own an expensive scanner. I use an all in one printer with a cheap scanning bed. I work in black and white, so I don’t worry about color loss. If you do worry about color loss, invest in a good quality scanner. If you do invest in a good scanner, avoid letting it get bumped or knocked around.

Prep your Image.

Before I scan, I erase all my line-work carefully, than I correct any problems I see.

I stick a piece of white paper between my sketchbook page and the next page, so the image on the page behind won’t bleed through.

These things make sure my scan comes out pretty good the first time. Re-scanning at the high resolution I want in takes time and I don’t always have that time.

So, these are my rules of scanning. What are your rules? Anything important that I missed? Let me know in a comment.