What about printouts and printers?

Printers these days usually print at either 300 or 600 dpi. Some will even print at 1200dpi. Big whup. The 300 to 600 dpi difference is visible if you squint a little. 1200 - not really. Something to think about - this is the resolution at which the printer prints - not necessarily what you get. Most color printers/plotters these days are inkjet - which means the ink soaks into the paper. Yes, it bleeds a little. Which means, if you want a visible resolution better than about 300, you will have to pay for special paper. The best is paper that is plastic coated with tons of little dimples (at 600dpi or better). The ink then pools in these little dimples and dries in place. However, this paper is expensive. The lesson here - don't waste money on high resolution printers if you're just going to stick plain old paper into it. However, with laser printers, what you print is what you see.

Because, as GIS pros, we are always working with large graphics files, we often max out our printers. Why, you might ask? Let's do the math here: ....

....a 1 inch by 1 inch graphic printing at 300 dpi. That translates to 300x300 = 90,000 pixels/dots. It's a photo, so 16 bit color - thus, 2 bytes are required to describe the color of each pixel. 90,000 pixels x 2 bytes/pixel = 180000 bytes to describe that single inch. Or 180 kilobytes. It doesn't matter what the file size is on your computer - the process of printing at that resolution requires a print file at that size.

One more example. You're making a big poster - with a nice color image as a background. Let's say, 24x36 inches. 24 bit color - because you're using 3 bands of Landsat Data (each band is 8 bit, the combo = 24 bit). You have a older plotter - 300 dpi. How big is this file? The math: 300x300 - 90000 dots in each inch. 24x36 inches = 864 square inches. 3 bytes to describe the color. 90000 x 864 x 3 = 233,280,000 bytes. Or just over 233 MB. This is huge. Newer plotters usually act as their own print server and have built-in harddrives. They can do it. Older ones, probably not. For example, our old HP650c was maxxed with 64MB of RAM (no harddrive or attached print server) - it would crash every time a large print file was sent - any file over 64MB. Remember, it's not the size of the graphics file on your computer - it's the size of the print file.

For the sake of argument - same issue, 600 dpi. The file size would be 4x larger - or nearly a gigabyte!

Remember this - you WILL encounter it one of these days....