Whether you're working digitally from scratch and want to know what size file to start with or you work in traditional media and you're trying to decide on scanner settings, there's a lot to know about creating electronic files of your artwork. These tips and tricks are also applicable to scanning photographs.

What's it For?

Defining your end product is your first hurdle. Do you desire only to create an image for the web, or are you creating an electronic archive of your work for posterity? Are you planning to have your artwork printed? What size prints do you want?

The files you create for these varying purposes will be vastly different in size and specifics. It is important to remember that you can generally make a file smaller without sacrificing quality, but it is almost impossible to make a file larger and not lose precious detail and resolution. I highly suggest that you aim high and plan for good quality print files, even if you don't think you'll do prints anytime soon. When I'm scanning in an original, even if I plan to use it only as a web image, I scan it as a high-resolution copy suitable for printing that I set read-only so that I never accidentally overwrite it with a low-resolution image. That way, even if I spill coffee all over the original, fifty years from now I still have the option of making prints.

The drawback to saving large files is, of course, that they are large. If you are painting digitally, this means your computer will slow down doing some of the more laborious tasks, and these files may take up valuable hard drive space. You should decide on a balance that keeps your computer happy and still maintains a file of decent quality.

Some Terminology:

Pixels: Most simply, these are the dots that a picture is composed of. If you imagine an art file as a grid, each pixel is a square, and it has a specific color associated with it. When you see '3 Megapixel' as a specification on a digital camera, it is telling you that the pictures it takes contain 3,000,000 pixels. If the pictures are square, this means that the image size is going to be about 1750 x 1750 pixels.

DPI: Literally, dpi stands for 'dots per inch.' Printer output is given in these terms, and a good quality printer generally prints 1200 dpi or higher. This is the number of dots of ink that the printer is lying down every inch. In terms of looking at a computer monitor, you are seeing something closer to 100 dpi. In this case, dpi refers to the number of individual points of color that your monitor shows you. A good quality print file will be about 300 dpi, which means the file has 300 pixels of information across every inch that will print out. A print file of 300 pixels per inch can be printed on a 2880 dpi printer with excellent quality. Note that the 'dots' that dpi is talking about are not always pixels; that is a common misconception.

Resolution: This term refers to the density of dots. A high-resolution file suitable for printing might be 300 dpi. A low-resolution file for web viewing would be more like 100 dpi. The resolution setting on your monitor indicates how many pixels it shows; a common setting is 1024 x 768, while a low resolution for a monitor would be 800 x 600.

'Vector image' or 'Raster image': A raster image is a file that is defined pixel by pixel. A line would be described as 'black dot here, black dot here, black dot here...' until the entire line was drawn. A vector image defines the geometry of the line, saying 'black line of such and so thickness from point a to point b'. Examples of vector images are those created in AutoCAD programs, or Adobe Illustrator. Examples of raster images are most standard image files, including jpegs and gifs. When you scan an image, you are creating a raster image. Some advantages of vector images include the fact that they are generally smaller in file size, and they will scale up or down indefinitely without any degradation, making them ideal for graphic design applications. Raster images, however, can be viewed, created and manipulated more commonly, and they allow more flexibility in terms of non-mathematical shapes.

CMYK, RGB, HSB, #, and Lab: These terms are basically different methods of describing every color in a file in a mathematical way. For a long time, CMYK (based on the standard cyan-magenta-yellow system) was an industry standard for printing, but you will find now that most print-systems are computer controlled and can easily convert between any of these systems. I personally save all of my files in RGB format.

Grayscale, Bitmap, Indexed and Duotone colors: Grayscale, as it sounds, is a picture that is composed entirely of pixels that are shades of gray, black or white. Bitmap settings (not to be confused with .bmp file types!) indicate that all of the pixels are either black or white. Bitmap-set drawings can still look like gray-scale drawings if the resolution is very high, blends being created by patterns of black and white at a very tiny scale. Similarly, Indexed color or duotone settings limit the palette of the drawing to a set number of colors.

Scanning Tips:

Scan at only a slightly higher resolution than you want your final product to be; there is generally no need to scan at the absolute highest resolution that modern scanners are capable of, and the higher resolution can be time consuming.

I scan black and white pencil work in a full-color setting; I find that it picks up some of the grayscale gradients a little better. Never scan a drawing with any shading in 'black and white text mode,' as this will convert all of your gray-shades into either black or white. I find that even black and white ink drawings are improved using a grayscale setting, as it smoothes the edges just a touch, and avoids a blocky, chunky-crayon look.

Some scanner software is not terribly sophisticated, and I recommend caution in using the picture adjustment options such as brightness/contrast or sharpen that are offered through your scanner program.

Some scanner software does not give an option for setting the specific dpi. Sometimes there is a sliding % bar, sometimes just a few pre-set options. My best recommendation here is to experiment with the settings, or invest in better software.

Sometimes the scanner will output a file that looks absurd, with very large dimensions at a low dpi, turning a little 5x7 photograph into a 36" behemoth at 50 dpi. This is a function of the scanner software also, and can be easily adjusted in image-editing software. Experiment to find the correct settings to output the correct number of pixels for the scanned image.

File Types:

There are more file types for images than there are impossible hairstyles in fantasy art. I'm going to just hit on some of the more common ones.

JPGs and GIFs are probably the most common file types. They can be interpreted by web browsers, and by just about any kind of image viewer and art program available. The biggest downside to this kind of file is the fact that they use compression to keep the file size small. Never, ever use a jpeg or a gif as a file that you will manipulate or save multiple times, as it re-compresses every time that you save it, leading to severe image degradation. If you have seen images that look vaguely blurry, with blocks of fuzz, over-compression is often the cause. If you have to re-size or adjust a jpeg or gif, I highly recommend saving the adjusted file as a separate file so that you retain all of the quality that you can in the original jpeg.

TIFs are far safer as a format for a file you may wish to make changes to.

Even safer than TIFs are program-specific files, such as PSD files (Photoshop) or Painter files, which can also contain information about layering, transparencies and hidden items. I work primarily in Photoshop, and save all of my files in that format, creating JPGs or GIFs from my archived files as I need them.

If you have difficulty saving an image in a format other than something program specific, check two things: your file modes, and your layers. Because most of these formats won't hold layer information, you may have to flatten your layers to save as a non-program format. Color palette restrictions and your bit depth may also restrict your file options.

Adjusting Files:

Re-sizing a picture can mean a couple of different things, and this is an easy point to get confused on. You can resize a picture by manually changing the number of pixels it is made up of, by changing the dimensions but not changing the resolution, or by changing the resolution but not changing the dimensions. You can even be really daring and change the dimensions *and* the resolution!

The actual pixel count is the dimension times the resolution. A 5" x 7" file at 300 dpi would have 1500 pixels across and 2100 pixels down. If you change the resolution of the file to 600 dpi, you still have a 5" x 7" print, but now you have 3000 x 4200 pixels.

When you are resizing a picture, imagine your picture as a grid, with a different color in each box (pixel). When you resize, you aren't making every block of the grid bigger, you're putting your image on a bigger grid and spreading out the information that you have. The art program goes and fills in all the missing information. Most art programs are pretty smart, and they will fill things in the way that they're supposed to be, but it's important to realize that the program is 'guessing,' so you don't want to resize an image more than once if you don't have to. The same is true with making an image smaller, except that the program is 'guessing' which boxes of color (pixels) to take away, rather than what boxes of color to add.

If you have a 24" x 36" file at 100 dpi, you can resize it to an 8" x 12" file at 300 dpi and it will have exactly the same number of pixels! You can do this indefinitely without fearing for any loss of information in your file, unlike changing the number of pixels in a file.

To make a file for viewing on a computer screen, use a resolution of 100 dpi, as this is close to what you will see on an average computer monitor (this depends on individual settings, but 100 dpi is a good average). To make an image look 2 inches wide on a screen, it should be about 200 pixels wide.

For a print file, 300 dpi is ideal. Higher resolution than that doesn't make a hill of beans of difference in print output. So if you want an 8" x 10" print, you want to make sure your picture is 2400 x 3000 pixels.

Wherever the option is available, choose 'constrain proportions.' This means that when you change the number of pixels in one direction (height, for example), the program automatically changes the number of pixels in the other direction (width, in this example) to match. This will prevent your image from looking stretched in one direction or the other.

Most scanners have a bit of a color or shading shift, and the resultant file is greatly improved with just a few touches in an art manipulation program. Most commonly, I find myself adjusting the brightness/contrast of a file to brighten the light spots and darken the dark spots, and I often adjust the hue to true up a flesh-tone. It is important to realize that the changes you make are permanent. If you increase the contrast of a picture to the point where there are large blocks of very dark and large blocks of very light, you cannot go back and restore all of the mid-tones that you started with unless you have saved the original scanned file.

Overall Recommendations:

I'll leave you with a couple of quick reference points, and hope, as always, that this article has been helpful!

Resizing: don't change the number of pixels more than you absolutely have to, and it's preferable to shrink something than to enlarge something.

Suggested computer viewing formats: 100 dpi in a JPG or GIF format.

Suggested print-quality formats: 300 dpi in a TIF or PSD format.