Color Calibration in the Field

现在什么都能拍高清了, there is so much more we can do, creatively, with all the new cameras available to us. 小型傻瓜相机可以用AVCHD编解码器拍摄720p30高清的整个活动, and be tucked anywhere out of sight, 捕捉到额外的小角度，否则无法捕捉到. 操作员可以“嵌入”人群中，并通过主摄像机看到, 然而，永远不要让别人注意到他们自己，因为他们没有拿着大的齿轮钻机.

但是你如何让你可能用来报道一个事件的所有不同的相机来匹配? 与我用第一台相机拍摄的漂亮的3芯片镜头相比, 我用较小的模特拍摄的镜头来充实我的镜头, the depth isn't there, the colorimetry, and so forth. 它不仅看起来不那么好，而且明显不匹配，吸引了人们的注意力.

But in trying to find ways to make the footage work, 让不同摄像机的比色法更接近以减少可见的变化, I came to the realization that, if we plan on using these cameras from the outset, 有一个技巧可以用来为每个摄像机设置一个颜色配置文件, 然后使用在那里建立的更正更正从您的项目的镜头的其余部分.

现在，这并不是适用于每一台相机，或在每一种情况下. Cameras that continually shift their colorimetry, white balance, and so on, will not work with this color correction methodology. But with most cameras, a simple tool gets you almost all the way, and your eye can determine the rest.

The Tool: Digital Target

The tool I am using is the 24in Digital Target from PhotoVisionVideo.com. This single target can be used as a reflector, 但神奇之处在于反光镜另一面的黑/灰/白条纹. In fact, I didn't get this to be used as a reflector at all; that's just a bonus. I got it specifically for color-matching disparate cameras.

The PhotoVision website is chock full of videos and samples. The videos are targeted to still photographers. 然而，视频相机和静态相机的原理是一样的. You need to be able to set a manual white balance. 你需要设置一个自定义白平衡——实际上，什么自定义白平衡并不重要, 但它需要被设置成一件事，这样白平衡在整个拍摄过程中不会改变——尤其是在你拍摄的瞬间或快速转弯，没有时间在后期匹配的情况下. That said, if you camera can't be set to a manual white balance, then this target and this article can't help you.

Automatic white balance is a moving target. 如果相机认为白点变冷了，它会自动使图像变暖. 如果相机认为图像变暖(更黄)，它将相应地冷却(更蓝)图像. Also, when things change within the shot, 当相机试图进行补偿时，它可以戏剧性地改变图像的白点. This will break the calibration process we build here.

一旦你所有的相机都设置了手动白平衡, 你需要把目标放在所有摄像机的前面——在相同的光线下. This means that you don't move the target around from room to room; you don't even rotate it inside a room or outside. It has to be sitting still. 所有的摄像机都必须从相同的位置记录目标, 因为反射光会因角度的不同而不同. 所以你不能同时从右边和左边射击目标，并期望这些射击能够匹配——这是不可能的.

一旦你有了所有的摄像机拍摄目标的画面, then they are free to go roam around, 但他们不能改变他们的白平衡或比色法(没有照片配置文件, or other settings that change color at all). You can't rebalance your color because if you do, 您将丢弃通过使用每个相机记录校准目标而创建的配置文件.

这并不意味着你不能再改变你的白平衡或设置. You can. 但是，每次您需要在任何相机中进行更改时，您都需要使用校准目标重新校准镜头. And you can't just recalibrate one camera; you have to recalibrate all the cameras, 这样你就有了一套新的校准配置文件，用于你将要拍摄的新照明情况.

You can see the setting for my "test" interview in Figure 1 (below). There's sky light coming in from a window on camera right, a little bit of daylight coming in from camera left, tungsten and fluorescent light coming from a ceiling light. What white balance would that be? And how would you set up two cameras to match? The answer: Fix it in post.

Figure 1. 一个高清摄像机和一个具有视频功能的静态摄像机，可以与来自PhotoVisionVideo的24英寸数字目标进行颜色匹配.com for my test interview setup