{"slug":"ps-channels-explained","title":"深入浅出理解Photoshop通道，学会调色和选区新技能","author":"Thomas看看世界","date":"2018-11-11","wechat":"https://mp.weixin.qq.com/s?__biz=MzI4NDA5MzE5NQ==&mid=2247487668&idx=1&sn=1a23af2b45f2dbec9b9affbf8d084586&chksm=eb81eed0dcf667c6596689d0d4f775ebd30d9eb7f015f4ded34b5457dd846910d8a96c2ee2d9&scene=21#wechat_redirect","blocks":[{"t":"h","x":"Thomas看看世界","xe":"Thomas Chu Photo"},{"t":"p","x":"每周一篇教程，让摄影不再难学","b":false,"xe":"One tutorial every week, making photography easy to learn"},{"t":"p","x":"在《PS的基石 － 图层与蒙板》一文中，托马斯和大家分享了Photoshop中的两个重要概念 - 图层、蒙版。","b":false,"xe":"In \"The Foundation of Photoshop: Layers and Masks,\" Thomas shared two important Photoshop concepts: layers and masks."},{"t":"p","x":"在今天的教程中，托马斯会和大家解释另外一个重要的后期概念 - 通道，并演示通道在后期修图，特别是制作选区时的应用。","b":false,"xe":"In today's tutorial, Thomas explains another key post-processing concept — channels — and demonstrates their use in editing, especially for making selections."},{"t":"h","x":"1","xe":"1"},{"t":"h","x":"通道是什么","xe":"What Are Channels?"},{"t":"p","x":"在电脑中，计算机需要找到一种方式去储存和描述数码图像。而通道就是一种用灰度图来描述数字信息的方式。","b":false,"xe":"A computer needs a way to store and describe digital images. A channel is one such way: using a grayscale map to describe digital information."},{"t":"p","x":"一个通道通常如下图那样，是一个黑白图像（灰度图像）。通道图上的每个像素，都对应了一个0-255的灰度值。","b":false,"xe":"A channel is typically a black-and-white (grayscale) image like the one below. Every pixel in a channel corresponds to a grayscale value from 0 to 255."},{"t":"img","f":"img-02","w":1054,"h":710},{"t":"p","x":"如果是一张黑白照片，那么我们用一个通道就能描述这张照片的所有信息。如果是彩色图像，就需要多个通道，才能完整的描述其色彩信息。","b":false,"xe":"For a black-and-white photo, a single channel describes all its information. A color image needs multiple channels to fully describe its color information."},{"t":"p","x":"计算机为了描述色彩，有RGB、CMYK、HSB、LAB等多种模式。如果用RGB的色彩模式，计算机就需要R（红）、G（绿）、B（蓝）三个通道来储存色彩信息。","b":false,"xe":"Computers describe color through modes such as RGB, CMYK, HSB, and LAB. In RGB mode, the computer needs three channels — R (red), G (green), B (blue) — to store color information."},{"t":"p","x":"（根据PS的规定，一张照片最多可以有56个通道来记录各种信息，所有通道都和图像有一样的长宽和像素值。）","b":false,"xe":"(Per Photoshop's rules, a photo can have up to 56 channels recording various kinds of information; all channels share the image's dimensions and pixel count.)"},{"t":"p","x":"下面一张数码照片，中间有一个红色圆形，其RGB色彩值是（200，100，50）。我们在Photoshop中打开这张照片。","b":false,"xe":"In the digital photo below, the red circle in the middle has an RGB value of (200, 100, 50). Let's open this photo in Photoshop."},{"t":"img","f":"img-03","w":1080,"h":716},{"t":"p","x":"在右下角“图层”面板的右侧，就是“通道”面板。对于RGB色彩模式下的图像而言，一共有红、绿、蓝3个基础通道，和一个RGB混合通道。","b":false,"xe":"To the right of the Layers panel in the bottom-right corner sits the Channels panel. For an image in RGB mode, there are three base channels — Red, Green, Blue — plus a composite RGB channel."},{"t":"p","x":"混合通道是基础通道通过一定的算法混合形成的，方便我们进行后期编辑。","b":false,"xe":"The composite channel is formed by algorithmically mixing the base channels, making editing more convenient."},{"t":"img","f":"img-04","w":306,"h":188},{"t":"p","x":"接下来我们可以依次点击预览一下红、绿、蓝三个通道，看看他们的不同。","b":false,"xe":"Next, we can click through the Red, Green, and Blue channels one by one to preview their differences."},{"t":"p","x":"下面这张就是红色通道中储存的灰度图，可以看到圆形处的亮度值为200，其实就是代表了圆形处色彩（200，100，50）中的R值200。","b":false,"xe":"Below is the grayscale map stored in the Red channel: the circle's brightness value is 200 — which is exactly the R value of the circle's color (200, 100, 50)."},{"t":"img","f":"img-05","w":1080,"h":719},{"t":"p","x":"下面这张是绿色通道中储存的灰度图，可以看到圆形处更深了，其亮度值变成了100，因为它代表了圆形处色彩（200，100，50）中的G值100。","b":false,"xe":"Below is the grayscale map in the Green channel: the circle looks darker, with a brightness of 100 — the G value of its color (200, 100, 50)."},{"t":"img","f":"img-06","w":1080,"h":716},{"t":"p","x":"下面这张是蓝色通道中储存的灰度图，圆形处显得更黑，亮度值为50，储存了圆形处色彩中的B值。","b":false,"xe":"Below is the grayscale map in the Blue channel: the circle looks darker still, with a brightness of 50 — the stored B value of its color."},{"t":"img","f":"img-07","w":1080,"h":713},{"t":"p","x":"简而言之，通道就是用来储存照片某些信息（比如亮度、颜色分量、不透明度等等）的灰度图。RGB模式下，图像有红、绿、蓝三个基本通道。","b":false,"xe":"In short, a channel is a grayscale map that stores certain information about a photo — brightness, color components, opacity, and so on. In RGB mode, an image has three base channels: Red, Green, and Blue."},{"t":"h","x":"2","xe":"2"},{"t":"h","x":"通道的应用","xe":"Applications of Channels"},{"t":"p","x":"通道的主要应用有两个，分别是调色和建立选区。","b":false,"xe":"Channels have two main applications: color grading and building selections."},{"t":"p","x":"由于RGB模式下，各个通道实际上是储存了不同颜色分量上的信息。因此我们可以通过直接改变通道的方式，调整照片的色彩。","b":false,"xe":"Since in RGB mode each channel stores information about one color component, we can adjust a photo's colors by directly modifying its channels."},{"t":"p","x":"因为通道是一种灰度图像。而我们以前学过的蒙版（选区）其实也是一种灰度图像。那么我们也可以把通道转换为蒙版（选区），在一些情况下实现更高效快捷的局部选择。","b":false,"xe":"A channel is a grayscale image — and so is the mask (selection) we learned about earlier. That means we can convert a channel into a mask (selection), making local selections more efficient in certain situations."},{"t":"p","x":"下图是我用来演示通道调色的一张照片，假设我想把照片往秋天的色彩调整，让整体色调更偏橙色。","b":false,"xe":"The photo below is my channel-grading demo. Suppose I want to push it toward autumn colors, making the overall tone more orange."},{"t":"p","x":"学过《学会后期调色，从认识颜色开始》的同学应该知道，本图中黄色和绿色占大部分，而黄色和绿色中增加红色，都可以让他们往橙色方向偏移。","b":false,"xe":"If you've read \"Learn Color Grading by Understanding Color First,\" you'll know this image is dominated by yellows and greens — and adding red to either shifts them toward orange."},{"t":"img","f":"img-08","w":1059,"h":706},{"t":"p","x":"红色通道储存了照片中色彩R、G、B中的R值，因此提亮红色通道，相当于提高照片中所有颜色的R值，增加红色。","b":false,"xe":"The Red channel stores the R value of every color in the photo, so brightening the Red channel raises the R value of all colors — adding red."},{"t":"p","x":"所以我们可以单独选择红色通道。","b":false,"xe":"So we can select the Red channel alone,"},{"t":"img","f":"img-09","w":1080,"h":481},{"t":"p","x":"然后选择“图像-调整-曲线”。","b":false,"xe":"then choose Image > Adjustments > Curves,"},{"t":"img","f":"img-10","w":535,"h":191},{"t":"p","x":"对曲线进行提亮，红色通道就被提亮了。","b":false,"xe":"and lift the curve — the Red channel is brightened."},{"t":"img","f":"img-11","w":1080,"h":548},{"t":"p","x":"这样照片就会更偏红色，呈现出橙黄色调。","b":false,"xe":"The photo then leans redder, taking on an orange-yellow tone."},{"t":"img","f":"img-12","w":1061,"h":703},{"t":"p","x":"当然Photoshop中还有专门利用通道进行调色的工具，比如通道曲线、通道混合器等，托马斯会在以后的教程中分享这些工具。","b":false,"xe":"Photoshop also has dedicated channel-based grading tools, such as channel curves and the Channel Mixer — Thomas will share those in future tutorials."},{"t":"img","f":"img-13","w":1063,"h":705},{"t":"p","x":"除了调色，通道的另外一个作用就是用来建立选区。因为不同的通道，其灰度图像是不一样的。同样一个边缘，会在不同的通道中显示出不同的反差，我们可以寻找反差最大的那个通道来建立选区。","b":false,"xe":"Beyond grading, channels also build selections. Different channels have different grayscale maps, so the same edge shows different contrast in different channels — we can pick the channel with the strongest contrast to build our selection."},{"t":"p","x":"比如下面这张照片，如果我想把天空单独选出来，并不是一件容易的事情，需要借助通道的帮助。","b":false,"xe":"In the photo below, for example, selecting only the sky is no easy task without the help of channels."},{"t":"img","f":"img-14","w":1080,"h":719},{"t":"p","x":"首先查看红色通道，红色通道中天空和树木反差不是很明显，不适合用来建立选区。","b":false,"xe":"Check the Red channel first: the contrast between sky and trees is weak — not suitable for a selection."},{"t":"img","f":"img-15","w":1080,"h":719},{"t":"p","x":"再看看绿色通道，绿色通道中天空和树木反差更强了，已经可以用来建立选区。","b":false,"xe":"Now the Green channel: stronger contrast between sky and trees — already usable."},{"t":"img","f":"img-16","w":1080,"h":720},{"t":"p","x":"不过我们再来看看蓝色通道，蓝色通道中天空很亮，树木很黑，天空和树木反差最大，最适合用来建立选区。","b":false,"xe":"But look at the Blue channel: the sky is bright, the trees are dark — the contrast is greatest here, making it the best choice for the selection."},{"t":"img","f":"img-17","w":1080,"h":718},{"t":"h","x":"3","xe":"3"},{"t":"h","x":"通道-选区-蒙版的转换","xe":"Converting Between Channels, Selections, and Masks"},{"t":"p","x":"通道，选区和蒙版之间，是可以相互转换的，接下来我们继续以这张照片为例，讲解如何把通道转换为选区，并进一步生成对应的蒙版。","b":false,"xe":"Channels, selections, and masks are interconvertible. Let's continue with this photo to see how a channel becomes a selection and then a mask."},{"t":"p","x":"进入“通道”面板，默认选择的是全部通道。","b":false,"xe":"Open the Channels panel; by default, all channels are selected."},{"t":"img","f":"img-18","w":302,"h":176},{"t":"p","x":"前面我们已经试验过，蓝色通道中天空和树木分离效果最好，所以我们鼠标左键，点击选取蓝色通道。","b":false,"xe":"We've established that the Blue channel separates sky from trees best, so left-click to select the Blue channel."},{"t":"img","f":"img-19","w":310,"h":314},{"t":"p","x":"要把蓝色通道转换成选区，只需要按住键盘上的“Ctrl”键，同时鼠标左键点击蓝色通道。","b":false,"xe":"To convert the Blue channel into a selection, hold Ctrl and left-click the Blue channel."},{"t":"img","f":"img-20","w":306,"h":338},{"t":"p","x":"此时画面中显示出蚂蚁线，我们已经顺利的把通道转换为选区。","b":false,"xe":"Marching ants now appear in the frame — we've successfully converted the channel into a selection."},{"t":"img","f":"img-21","w":1080,"h":721},{"t":"p","x":"重新用鼠标左键，点击RGB通道前的方框，就可以回到正常的全部通道预览模式。","b":false,"xe":"Left-click the box in front of the RGB channel to return to the normal all-channels preview."},{"t":"img","f":"img-22","w":303,"h":296},{"t":"p","x":"将选区继续转换为图层蒙版，一共有三种情况：","b":false,"xe":"There are three cases when converting a selection into a layer mask:"},{"t":"p","x":"1）转换为新建调整图层的蒙版。","b":false,"xe":"1) Converting it into the mask of a new adjustment layer."},{"t":"p","x":"Photoshop在新建曲线、色阶、可选颜色等等调整图层的时候，会自动对其建立蒙版。如果没有选区，会自动生成白色蒙版。如果已经加载选区，会自动生成选区对应的蒙版。","b":false,"xe":"When you create an adjustment layer — Curves, Levels, Selective Color, and so on — Photoshop automatically gives it a mask: a white mask if no selection is loaded, or a mask matching the selection if one is."},{"t":"img","f":"img-23","w":1080,"h":524},{"t":"p","x":"比如在刚刚已经获得蓝色通道选区的情况下，我们新建曲线调整图层。","b":false,"xe":"For example, with the Blue channel selection loaded, let's create a Curves adjustment layer."},{"t":"img","f":"img-24","w":317,"h":470},{"t":"p","x":"选区就被自动创建成了曲线的图层蒙版，这个蒙版的灰度图和蓝色通道一模一样，树木区域是深灰色，基本不会受曲线调整影响。天空部分是浅灰色，会受到曲线调整作用。","b":false,"xe":"The selection is automatically turned into the Curves layer mask, whose grayscale map is identical to the Blue channel: the tree areas are dark grey and barely affected by the curve, while the sky areas are light grey and receive the adjustment."},{"t":"img","f":"img-25","w":1080,"h":548},{"t":"p","x":"我们不妨试着在曲线上建一个点，进行提亮。可以看到画面中只有天空被提亮，地景几乎不受影响。","b":false,"xe":"Try adding a point on the curve and lifting it: only the sky brightens; the landscape is nearly unaffected."},{"t":"img","f":"img-26","w":1080,"h":551},{"t":"p","x":"2）第二种情况，是蒙版需要增加到一个普通图层上面。","b":false,"xe":"2) The second case: adding a mask to a normal layer."},{"t":"img","f":"img-27","w":309,"h":519},{"t":"p","x":"在没有选区的时候，点击画面右下角的“添加图层蒙版”按钮，会自动生成白色蒙版。在已有选区的情况下，点击画面右下角的“添加图层蒙版”按钮，会自动生成选区对应蒙版。","b":false,"xe":"With no selection loaded, clicking the \"Add Layer Mask\" button at the bottom-right of the panel creates a white mask. With a selection loaded, the same button creates a mask matching the selection."},{"t":"img","f":"img-28","w":320,"h":108},{"t":"p","x":"3）最后一种情况，是要添加蒙版的图层已经有一个蒙版了，要对已有蒙版进行替换。","b":false,"xe":"3) The last case: the target layer already has a mask that you want to replace."},{"t":"img","f":"img-29","w":305,"h":106},{"t":"p","x":"这种情况也很简单，鼠标右键点击要替换的图层蒙版图标，在菜单中选择“删除图层蒙版”。","b":false,"xe":"This is simple too: right-click the existing layer mask icon and choose \"Delete Layer Mask\" from the menu."},{"t":"img","f":"img-30","w":312,"h":253},{"t":"p","x":"删掉图层蒙版后，这个图层就变为没有蒙版的状态了。","b":false,"xe":"Once deleted, the layer is back to having no mask."},{"t":"img","f":"img-31","w":300,"h":456},{"t":"p","x":"之后的操作和（2）就一模一样了，在加载选区的情况下，添加图层蒙版，选区就会转换为蒙版。","b":false,"xe":"Then proceed exactly as in case (2): with the selection loaded, add a layer mask, and the selection converts into the mask."},{"t":"img","f":"img-32","w":1080,"h":549},{"t":"p","x":"除了通道可以转换为选区之外，选区也可以转换成通道进行储存。我们用其他工具如快速选择工具建立的选区，可以储存在通道中，以备再用。","b":false,"xe":"Just as channels convert into selections, selections can be stored as channels. Selections made with other tools, like Quick Selection, can be saved into a channel for later reuse."},{"t":"img","f":"img-33","w":1080,"h":729},{"t":"p","x":"在已有选区的情况下，进入通道面板，点击下方第二个图标“将选区储存为通道”。","b":false,"xe":"With a selection loaded, go to the Channels panel and click the second icon at the bottom: \"Save Selection as Channel.\""},{"t":"img","f":"img-34","w":320,"h":228},{"t":"p","x":"这样通道面板中就会新生成一个Alpha通道来储存选区。之所以叫做Alpha通道，是因为这个通道不同于照片自带的R、G、B色彩通道，并不会影响照片的色彩显示。Alpha通道只是一种用来储存选区的方式。","b":false,"xe":"A new Alpha channel then appears in the Channels panel, storing the selection. It's called an Alpha channel because — unlike the photo's native R, G, B color channels — it doesn't affect how the photo's colors display. An Alpha channel is simply a way to store a selection."},{"t":"img","f":"img-35","w":1080,"h":537},{"t":"p","x":"按住Ctrl键的同时点击Alpha通道，或者用通道面板下方的第一个图标，可以把Alpha通道重新转换为选区。","b":false,"xe":"Hold Ctrl and click the Alpha channel, or use the first icon at the bottom of the Channels panel, to convert the Alpha channel back into a selection."},{"t":"h","x":"4","xe":"4"},{"t":"h","x":"通道/蒙版的修改和提纯","xe":"Refining Channels and Masks"},{"t":"p","x":"最后我再来演示一下，如何对生成的蒙版区域进一步修改，得到更准确的选择。比如前面演示的这个蒙版为例。","b":false,"xe":"Finally, let me demonstrate how to further refine a generated mask for a more accurate selection, using the mask from earlier."},{"t":"p","x":"按住Alt键，同时点击图层蒙版图标，可以切换到蒙版预览模式。此时照片栏会从显示彩色照片，改为显示图层所携带的蒙版。接着进入“图像-调整-曲线”工具。","b":false,"xe":"Hold Alt and click the layer mask icon to switch to mask preview: the image view changes from the color photo to the layer's mask. Then open Image > Adjustments > Curves."},{"t":"img","f":"img-36","w":524,"h":202},{"t":"p","x":"选择曲线的抓手，吸取画面的天空部分，然后上提曲线。此时蒙版的天空部分就会变亮（当然因为现在曲线上只有一个点，所以上提这点整个曲线都会上提，整个蒙版都变亮）。","b":false,"xe":"Take the Curves hand tool, click on the sky area of the image, and drag the curve up — the sky portion of the mask brightens. (With only one point on the curve, lifting it lifts the whole curve, brightening the entire mask.)"},{"t":"img","f":"img-37","w":1080,"h":663},{"t":"p","x":"再用抓手吸取画面的树干部分，往下压曲线，这样蒙版中的树木部分就变得更黑了。通过曲线的两步操作，天空部分更白，地景部分更黑，选区就选的更加准确了。","b":false,"xe":"Then use the hand tool on the tree trunks and drag the curve down — the tree portion of the mask darkens. After these two curve moves, the sky is whiter and the landscape blacker: a more accurate selection."},{"t":"p","x":"我们通过将蓝色通道转换为蒙版，并进一步的强化蒙版反差，就得到了仅仅选择天空部分的精细蒙版。","b":false,"xe":"By converting the Blue channel into a mask and then strengthening the mask's contrast, we obtain a refined mask that selects only the sky."},{"t":"img","f":"img-38","w":1080,"h":648},{"t":"p","x":"通道、蒙版除了可以用曲线工具来修改之外，还可以通过计算的方式来修改。而我们常说的亮度蒙版，其实就是对通道进行进一步计算生成的，我们会在后面的教程中和大家进一步分享。","b":false,"xe":"Beyond Curves, channels and masks can also be modified through calculations — the luminosity masks we often talk about are generated by further calculations on channels. We'll share more in future tutorials."},{"t":"h","x":"欢迎关注@Thomas看看世界，","xe":"Follow @Thomas Chu Photo,"},{"t":"h","x":"每周学会一个摄影技能。","xe":"and learn one photography skill every week."}],"titleEn":"Photoshop Channels Explained: Master Color Grading and Selection Skills"}