Accu-Chart HGSG. 11 Step Grey Scale, Gamma Compensated

The Accu-Chart HGSC Grey Scale chart is used in conjunction with a waveform monitor to adjust the light response characteristics (video levels of Gamma) of the camera and to ensure that these characteristics are matched in all three color channels. It is also used to adjust shading and flare. The 11-Step Grey Scale Chart is an extended range test chart intended for use with high-performance video cameras including both CCD and tube types. The chart consists of two arrays of 11 neutral grey patches or "chips" ranging in reflectance from 2% of approximately 90% (about 5.5 f-stops). The arrays are arranged so that one increases in reflectance from right to left and the other increases left to right. The strips are mounted on a uniform grey background with a reflectance of 16%. A black-white-black test object in the center of the chart provides a black ( The grey scale values are chosen according to a power law producing a "Gamma" value of 2.2, the characteristic value for television receivers and monitors. To provide an overall system gamma of unity, the video camera is usually adjusted to a Gamma of 1/2.2=0.45. With the Gamma Compensated Chart, the video Signal from a camera adjusted to that value will appear as a linear "staircase" (equal steps) when viewed on a waveform monitor. Measures 10" x 12.5"