To achieve consistent and quality color reproduction it is necessary to understand the colorimetric characteristics of the devices that are included in the process of graphic reproduction. Color management system has a role in controlling and adjusting the color information through the system of graphic reproduction. In this process the profiles of the devices have a big part. Production of the device profiles includes their calibration and characterization. Calibration is the process of maintaining a device with defined and known characteristics so the gained results can be reproducible again. Characterization process serves as a connection between the devices with independent and dependent color space. Monitor characterization presents a big step in color management system. The technology changes so fast that the characterization has to be adjustable to different types of monitors. GOG (short for Gain-Offset- Gamma) model is precise enough to describe the tone reproduction curve for monitors based on cathode tube, but it is not adequate enough to characterize LCD (short for Liquid Crystal Display) monitors. LCD monitors have big space resolution and bigger dynamic range so the expansion of existing GOG model is needed.