Screen and printer calibration
Another important technique for ensuring that what you see onscreen is accurate is to calibrate your monitor with a hardware calibration device.
These third-party sensors plug into the USB outlet on the computer and hang over the screen. Run the associated software and the sensor will determine whether the RGB colors displayed onscreen really are 100% red, green, blue, white, gray, and black. If the screen is different from the known values for these colors, the software adjusts the brightness and color to make it display correctly. This is a far more accurate method of color management than using the human eye to gauge the settings. As a general rule, screens need calibrating every six months or so, especially if they are used a lot.
Screen calibration: Attaching a USB-powered hardware calibrator to the laptop or desktop screen is easy. Pictured is the (reasonably inexpensive) ColorVision Spyder5 device. This process needs to be done (probably) once every six months or so, to ensure that what you see onscreen is a realistic representation of the original image. It does not ensure print accuracy—that's the job of another device (see below).
Printer calibration: Making what comes out in print look exactly the same as what's seen onscreen is a slightly trickier and more expensive operation.
For this you need another scanner that can read both screens and test prints. It takes longer to print and scan the resulting chequerboard of colors, but once done, the accuracy of screen-to-printed paper is exceptional.
