A temperature measurement scale where 0° Kelvin (0°K) is equal to absolute zero, the temperature at which all molecular movement ceases. One degree of Kelvin is equal to 1 degree of Celsius. The color temperature of large image devices is measured in Kelvin. The higher the temperature, the bluer the light.

Keystoning occurs when the projector is not perpendicular to the screen, thereby creating an image that is not rectangular.

Keystone correction makes a projected image rectangular. This can be accomplished by positioning the projector to be perpendicular to the screen. Since this is not always possible, most projectors are equipped with keystone correction that allows the image to be keystone corrected (made rectangular) by adjusting optics, making mechanical adjustments, or applying digital scaling to the image. Keystone correction can be one or two dimensional and manual or automatic depending on the projector and the manufacturer. Be aware that digital scaling will introduce some artifacts that are more evident when viewing small text and less evident in presentation type material or video.