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用DaVinci去除佳能单反RAW视频出现的伪色高光点

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发表于 2014-11-13 16:24:43 | 显示全部楼层 |阅读模式
本帖最后由 jessica 于 2014-11-13 16:28 编辑


      在Magic Lantern 拍摄RAW视频的纯RAW后期剪辑调色流程一文中提到,佳能单反拍摄的RAW视频在DaVinci的流程里会有烦人的伪色高光影响最终画质,有人问起解决方案,那么这里特别分享一篇文章来解释。
      这个其实是个不成熟的解决方案,算是不得已而为之的,由于到目前为止DaVinci对佳能单反拍出的RAW视频文件(14bit的标准dng序列)还没有完美支持,佳能的拜耳阵列在解析的时候高反差部分尤其是高光部分会出现部分红色和蓝色的小点,国外有人称之为pink highlight,不管它叫什么,反正是不应该出现的。目前貌似只有Adobe公司自家的软件如ACR可以正确解析完美识别而不出现伪色,要知道用于通用RAWDNG格式就是Adobe公司提出来的,鬼知道是不是它没有把关键技术细节公开。但是我在前文也多次提到,通过ACRdng转成tiff确实效果不错,但是一不小心就会损失高光和暗部细节,而且这个流程耗时耗力,不到万不得已一般不用。好在这些伪色小点颜色够纯,在DaVinci中还是有办法解决的。
      下面直接把老外的文章转过来,很简单的方法,就不翻译了,个人的做法稍有区别,最后一步会用DaVinci自带的降噪功能而不是文中提到的模糊功能,当然对于没有买完整版的朋友,Lite版是不能使用降噪的,用模糊也能达到差不多的效果。
      pink highlight removing/noise reduction and sharpening in Davinci Resolve Lite
      Hey guys, just wanted to share some info i found out when using Davinci Resolve.I had some problem with pink highlights, especially when i wanted to sharpen myvideo.After some trial and error i found a way to decrease the pink highlight and gain better sharpness without boosting the pinkyness.RAW file with color space set to BMD Film for maximum Dynamic Range
      CC’ed shot with sharpening applied
      CC’ed shot with sharpening and pink removal
      Basically what i did was to add a layer mixer node as very last step as you can see here:
      The layer mixer node composite needs to be set to add in order to work for this removal.Now the two nodes it created before the final layer mixer node are the ones where going to work in.Set the top node to 0% saturation and pull down the Y gain on the bottom node like this:
      Now what we did was separate the Chrominance from the luminance, this means that the top node contains the information of exposure and the bottom node contains the information about the color.If we add a simple sharpening to the top node it only sharpens the black and white channels and doesn’t touch the color noise meaning a cleaner/sharper image than you would have with normal sharpening.Now we added some sharpening to the top node so we need to do the opposite thing to the bottom node.So go ahead and open the sharpen/blur tab for the bottom node.
      Make sure that you turn off the gang button (it’s the tiny shackles on the top left in the picture above), this gives you access to adjust the levels individually. Now these are the settings that worked for me in this picture, just try it on your picture because the settings could of course be a bit different.
      If you pull up (meaning less color) the red channel radius you will see that the pink highlight is disappearing together with the red color noise if you shot at higher ISO’s.Now you can use the other 2 channels too to remove some more unwanted color noise, and this trick only removes the color from that color noise meaning more detail with noise reduction turned on instead of blurring the whole picture as the normal noise reduction does.And there you have it, less noise, no pink highlights and a sharper picture WITHOUT losing detail!
Now i wouldn’t say that this is the best or only way, it’s just the only way i found out to do this.Hopefully it could help some of you guys.
      考虑到有部分朋友可能对英文比较晕,特别提供一段视频,更直观,更易懂。

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发表于 2014-11-13 19:13:03 | 显示全部楼层
有英语的也不错,自己去找很难找到。谢谢。
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发表于 2014-11-14 22:31:14 | 显示全部楼层
谢谢!!
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