Video Standards and Calibration:

2017-09-01 15:50:57 来源:影音中国

greg-v2.jpg

Gregg Loewen

THX视频培训首席讲师、Lion AV顾问公司创始人


Video standards have been adhered to since the being of video. These standards allow for content creators, broadcasters, and viewers to watch the content “as the creator intended”. If each step in the video workflow is not properly setup (ie: calibrated), the director's intention will be lost due to changing of the video signal by potential loss of white levels (clippin), black levels (crushing), or incorrect color rendition. Therefore, it is important for each step of the video workflow to be properly calibrated. The THX Video Training Program is 4 days in length and is based on the premise that the attendee must “do” to learn, meaning that hands-on learning is an essential class element. The attendee learns the basics of Color Science and the rules of video standards, then applies this knowledge to video setup and calibration, under the closely supervised mentorship of video setup experts. This article touches on many of the basics that are taught in THX Video Training, Level I. The complete 4 day program is being offered in Shanghai in November 2-5th 2017.

 

自从有了视频,就有了需要坚持的视频标准。这些视频标准让内容的创造者、广播员、观众都能按照创作者的意图来观看视频内容。如果视频工作流程的每一步都没有被恰当地设置的话,视频信号将会改变,比如潜在的白电平、黑电平细节的损失或者不正确的颜色再现,这些都会导致导演意图的丢失。所以,调校视频工作流程的每一步都至关重要。THX视频培训长达4天,以学员必须动手实践所学内容为前提,这也意味着实践学习将成为课程内容的重要部分。学习内容包括色彩科学和视频标准规则,然后在相关视频专家的监督指导下,将这些知识运用到视频设置和调校。这篇文章谈及的就是THX视频培训1级的许多相关基础知识。完整的THX Video 1/2以及HDR视频认证工程师培训课将于2017年11月2-5日在上海举办。2号是THX视频一级认证工程师培训,3-4号是THX视频二级认证工程师培训,5号是HDR动手实验培训。


The basics基础知识


When calibrating the display the first thing to adjust is the display's mode or “preset”. The preset is a of factory adjustments that provide a certain look on the display when the preset mode is selected. Typical preset modes include: Sports, Vivid, Standard, Movie, and perhaps Custom. If the display has passed THX Certification there will also be a THX Mode and this preset should be selected. If not THX Certified, then select Movie Mode. Custom Mode is also an option. Custom Mode assures that there are the proper controls in the menus to allow for calibration.


调校显示设备的第一件事情是调整显示模式或预设模式。我们首次开启设备 , 看 到 的 就 是 工 厂 设 置 好 的 预 设 模式 。 典 型 的 预 设 模 式 包 括 : 运 动 、 鲜艳、标准、电影或自定义。如果显示设备已经经过THX认证,用户将能看到THX模式,并且应该选择这个模式。如果没有THX认证,那么电影模式、自定义模式也是比较恰当的选择。自定义模式能确保调校时菜单有恰当的输入。


The video signal in the current broadcast standard is in 8 bits. This means that there are 256 distinct steps when transitioning from the darkest blacks to brightest whites. In post production and in Ultra High Definition (UHD) the signal can be in 10, 12, or even 14 bits, which allows for more steps in the transition from black to white and therefore a smoother signal. This also requires much more bandwidth. When calibrating a display we need to ensure we can see each of these video steps. 


目前广播标准的视频信号是8bit,这意味着从最黑的黑色过渡到最亮的白色,有256阶过渡。在后期制作、超高清领域,信号可以达到10、12甚至14bit,黑色到白色将有更丰富的过渡,视频信号将显得更加平顺。这也需要更大的频宽。因为当调整显示设备时,我们必须确保能看到每一个视频信号的过渡细节。


The basic display controls are commonly referred to as the “front panel controls”. These controls, along with selection of the correct mode preset will ensure a somewhat calibrated imaged. To ensure optimal reproduction of the director's intent, a THX Video Professional should be consulted to use specific video training along with video measurement tools to optimize the display to the next level of image fidelity.


基础的控制菜单一般被称为“前面板控制菜单”,这些控制选项,包括正确的预设模式的选择,将能确保一定程度的调校成像。但为了确保能最理想化地还原导演的意图,还是建议咨询一个THX视频专业人员,通过特定的视频培训和视频测试工具,将显示的影像精确度优化到更高级别。


The most important control to adjust is the black level control. Most manufacturers refer to this control as the brightness control. While viewing the THX PLUGE pattern, adjust this control so the shadow of the THX logo becomes hidden in the background but the logo itself remains visible. 


最重要的是黑电平的调整。大部分的制造商会将它用作亮度的调整。当观看一个THX PLUGE测试图案时,调整这个按键,直到THX logo字体的阴影隐藏到背景,但logo本身保持清晰可见。


Next, adjust the contrast对比度 control. This control may also be referred to as the picture control and adjusts the bright part of image. While viewing the THX Contrast pattern adjust the control up until some of the 8 boxes disappear, then turn it down a few clicks until all the 8 boxes are viewable. On some displays the boxes may not disappear, this is by manufacturer design and not a problem. On most projectors the 8 boxes may start to disappear by the 50% setting and the correct setting may actually at less than the 50% setting. This is also by design. 


接下来,我们调整对比度的控制选项。这个选项通常被称为图像管理,用来调整图像的亮度部分。当观看THX的对比度测试图案时,将按键往上调,直到全部八个的格子消失,然后再将它往下 调 一 些 , 直 到 全 部 八 个 格 子 都 看 得见。在一些显示设备上,这些格子将不会出现,这和制作商的设计有关,不是什么问题。而在大部分的投影机上,所有八个格子将会在对比度调整到50%的时候消失,当然正确的设计应该是低于50%。这些都是设计的问题。


TestPat_WhiteDetail.png

大部分的投影机上,所有八个格子将会在对比度调整到50%的时候消失


When the black level and contrast are correctly set the display will be showing its optimized dynamic range. There may also be a back light control. This control adjusts the overall light output of the display, and should be set as to not make the display too uncomfortably bright or dark to look at (when considering a dark environment or a bright room environment). A THX Video Professional will use instrumentation to actually measure and adjust for the correct amount of light output. 


当黑电平和对比度都被正确设置之后,显示设备将会展示它优化后的动态范围。除此之外,还有背景光的设置。这个选项是用来调整显示设备的整体亮度输出,主要是考虑到在暗或亮的环境中,不会因为显示设备太暗或太亮而造成观看的不适。如果是一个THX专业人员,将会使用工具来测量和调整最终亮度输出的正确总量。


Once the useable dynamic range is set, the color saturation may be adjusted. Using the THX Color Pattern and THX blue glasses, adjust the color control so both the C and the O in the word color appear at the same intensity. If the display has a blue only mode, this can be used if THX blue glasses are not available. 


一旦可使用的动态范围被设定,那么色彩饱和度也应该调整。使用THX的Color测试图案和蓝色滤镜,调节“色彩”调整选项,直到图案上的C和O字母都看起来一样亮。如果没有THX的蓝色滤镜,而显示设备仅有一个蓝色模式,也可以选择这个进行调整。


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使用THX的Color测试图案和蓝色滤镜,调整颜色按键,直到图片上的C和O字母亮度都显示出同样的强度


Next consider the aspect ratio and sharpness. Using the THX Geometry pattern ensure that the circles are round and not cut off by the edges of the screen, then consider sharpness. The correct sharpness setting should be one where any dark lines should look crisp but not have haloing or false edges to them. On many displays, the correct sharpness setting may be at zero. 


接下来我们考虑一下画面比例和锐度。首先使用THX的几何测试图案,确保圆形是完整的,边缘没有被屏幕切掉。锐度方面,正确的锐度设置应该是所有的黑边都看起来锐利,周围没有白圈或其 它 错 误 的 边 缘 。 对 很 多 显 示 设 备 来说,正确的锐度调整应该是设定在0。


ͼ4.png

使用THX的几何测试图案来调整画面比例时,确保圆形是完整的,边缘没有被屏幕切掉


Finally look at some reference control to consider the quality of your work. Do humans and flesh toneslook reasonable / normal? Does green grass, blue sky, and other colors look good and not over-saturated? Now relax and enjoy the movie! 


最后,考虑到你最终的视频调校质量,我们还是要关注一些参考级的指标。比如人的肤色看起来自然吗?绿色的草地、蓝色的天空或其它颜色看起来舒服吗?会不会过于饱和?如果都没有问题的话,你就可以放松一下享受电影了!


ͼ5.png

人的肤色看起来是否自然是参考级指标之一,恰当的颜色不应该过于饱和 


Taking your video display to the next level

将你的视频显示调整到更高级别


The above article is a quick summary of basic display setup. Many consumers and movie imaging professionals desire a higher level of display accuracy along with more precise color calibration.  This is especially so as video standards have been quickly changing and evolving over the past decade and moving from DVD (480p) to BluRay (1080p) to UHD (3840p). Along with increased image resolutions, color gamuts have also increased as have gamma targets and light output requirements. High Dynamic Range (HDR) is now also in the marketplace and requires precise calibration for the discerning viewer. It is the goal of THX Video Training to discuss, educate, and provide a hands on learning environment to allow for attendees to understand and then master the skills required to professionally setup video displays and video systems there by allowing the viewer to watch the content “as the creator intended”. 


上文是基本视频显示设置的快速摘要。大部分的观众和电影图像的专业人员需要一个更高级别的显示精确度以及更 精 准 的 色 彩 调 校 。 所 以 在 过 去 的 十年 间 , 视 频 标 准 总 在 快 速 地 演 变 , 从DVD (480p) 到蓝光 (1080p) 再到超高清 (3840p)。随着图像分辨率的增加,色域也跟着gamma目标值和光线输出的需要而增加。高动态范围(HDR)现在也出现在市场上,对于视觉敏锐的观众来说,它需要更加精确的调校。THX视频培训的目标就是让学员在讨论和培训的学习环境中,明白并掌握视频显示和系统的专业技能。经过仔细调校的视频,可以让观众欣赏到忠实还原创造者意图的内容。 


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