伽玛测量测试卡简介

　　伽玛测量测试卡TE205用于检查相机的伽玛设置。该图显示了1-10%透射的10个灰阶和10-100%透射的10个灰阶。

　　这些值的公差为±0.5%，使用时应设置为100%步长为700 mV，0%至0mV。伽玛测量测试卡显示的两列灰阶透射值：
      The tolerance for these values is ± 0.5%，Use should be set to 100% step length of 700 mV, 0% to 0mV.

　　Introduction to gamma measurement test cards

　　The gamma measurement test card TE205 is used to check the camera's gamma settings. The figure shows 10 gray scales of 10% transmission and 10 gray scales of 10-100% transmission.

　　Gamma measurement test card shows two rows of gray scale transmission values:

　　一个问题是几个相机厂商故意“打散”黑色，以提高噪音性能。这应该用在相机上选择的所需伽马定律来完成(除非你使用线性伽马来校准图表，这也假定当相机被选择为线性时，它实际上是线性的)。然后，需要知道对于各种输入电平应该输出什么选择的伽马定律。

　　这使得很难将主黑色正确设置为0 mV。实际上，应该设置主黑色，以使黑色中的噪声刚刚开始显示在波形轨迹上。然后应将波形监视器(最佳选择Tektronix 1781)设置为“相对”模式，并使用光标在黑色和100%步长上，按“参考”。范围然后直接在%中读出。最好使用低通或亮度滤波器来限制带宽。

　　对于0.45(在整个范围上)的伽马，信号(%)应该是：

　One problem is that several camera manufacturers deliberately "break away" black to improve noise performance. This should be done with the required gamma law selected on the camera (unless you use linear gamma to calibrate the chart, which also assumes that it is actually linear when the camera is selected as linear). Then, it is necessary to know what gamma law should be chosen for each input level.

　　For a gamma of 0.45 (over the entire range), the signal (%) should be:

　　除了0.45伽玛之外，4%的步进应该给出20%的输出，20%的输入应该给出50%的输出。初始斜率通常是固定的，因此相机变量伽马将被设置为从图表的20%步长提供所需的50%输出。还存在使用中的其它伽马定律，即BBC。 BBC-伽马对于第一个4%(大约)输入具有5次的初始斜率，然后进入0.4的伽马曲线。 

　　In addition to the 0.45 gamma, there are other gamma laws in use, the BBC. BBC-Gamma has an initial slope of 5 for the first 4% (approximately) input, and then enters the gamma curve of 0.4. 4% of the steps should be given 20% of the output, 20% of the input should be given 50% of the output. The initial slope is usually fixed, so the camera variable gamma will be set to provide the desired 50% output from the chart's 20% step.