"Calculation" is for masks.
People often ask me, Su Se, how to use calculation tools? What are calculation tools used for? How can I master "calculation"?
For students who are new to PS, the first time they come into contact with the "calculation" tool is probably the steps of the channel dermabrasion method, which are introduced on the Internet. They select a green channel with moderate contrast, then retain the high contrast, then calculate, then retain the high contrast, and then Calculate, then High Contrast Preserve, then Calculate again... Yes, we don't know the principle, why during the calculation we choose the "Hard Light" blending mode of Green Channel Copy to Green Channel Copy instead of What about choosing "Darken" or another blending mode? We memorized the process step by step and came up with the desired effect, but why is there such a beauty in calculation tools???
Looking at the Internet, there are very few introductions to computing applications. Even if they are, they only introduce the methods without elaborating the principles.
I won’t elaborate on the channel dermabrasion method. Ultimately, this method is a thorough application of the channel as a selection function. It uses calculation tools to select the parts of the character’s skin that need to be brightened and beautified. “Calculation” is the function of the channel. A means or tool of choice.
Calculating and applying images, and layer blending modes are both related and different. To understand the role of calculation and be proficient in using it for yourself, you need to have a preliminary understanding of channels and layer blending. So today, Through two simple examples, I will tell you how the "calculation" tool works and what role it plays!
First: the "calculation" tool is closely related to the channel. It is generated by calculation in the channel to form a new ALPHA dedicated channel. The ALPHA channel is also the selected part we need. The channel is the selection area. I have talked about the function of the channel more than once. In fact, "calculation" is also a tool for generating the "selection area" function of the channel;
Second: Friends who know the "Apply Image" tool should understand that "Apply Image" directly acts on this layer and is irreversible, while "Calculate" forms a new candidate area in the channel, which is a candidate or backup. of.
Third: "Calculation", "Apply Image" and layer blending mode are closely connected. To understand layer blending mode, you must systematically understand the basic applications of PS starting from color. The application of layer blending mode is something you should be proficient in when learning PS at the intermediate stage. For those who have mastered and understood, the proportions or formulas of each mixing mode are provided in the appendix. Students can compare and master them in application, so they will not be elaborated here.
Fourth: "Layer blending" is the mixing of layers with a certain ratio in a certain mode, and "layer blending" is the relationship between layers.
"Apply image" is a direct effect on the channels (including RGB channels or ALPHA channels) in a layer using the "layer blending" mixing mode - essentially treating the channels (including RGB channels or ALPHA channels) as A kind of mixing between layers, but the subject of this mixing is a single channel or RGB channel in the layer. It is a channel-to-channel effect that directly produces a result on a single layer. The result of "Apply Image" is a single The layer has changed. As for "calculation", let's first look at the results. The results of calculation are neither visual changes in layer blending like layer-to-layer blending, nor are they changes in a single layer like "applying images". The essence of the "Calculate" tool is to use the "Layer Mixing" mode to mix between channels to generate a new selection. This selection is needed for our next operation.
After understanding these points, we use examples to understand how calculation can make selections for our use!! This is the most critical point to master the "calculation" method. We photography enthusiasts get a picture with purpose and purpose. To photoshop ideas, instead of blindly imagining things, breaking away from reality, breaking away from perspective, breaking away from photographic language, and breaking up aesthetics, we need to develop a habit of doing the same in the later stage of photography as in the early stage. Before picking up the camera and taking a picture, we should think about what the picture will look like. In the same way, we When we get a picture to be photoshopped, we should also develop the habit of thinking about what we will do or how we will do it before we do it. The key here is that we fully understand the proportional relationship between light and color in layer mixing. This is a hurdle from beginner to advanced applications!
To understand this hurdle, use the tools of "Layer Blending", "Apply Image", and "Calculate". To leap over this hurdle, among them, "Layer Mixing" and "Apply Image" are relatively intuitive, while "Calculation Tools" are relatively graceful, so let's remove the mystery of these tools, follow Su Se's actual operation and understand it. !!
Attachment: The following reprinted knowledge introduces the application of layer blending mode - master it skillfully in practice -
Blending modes can tightly combine the color values of two layers to create a wide range of effects.
Blending modes are very widely used in Photoshop. Most painting tools or editing adjustment tools can use blending modes, so the correct and flexible use of various blending modes can enhance the effect of the image.
Click the drop-down combo box of the layer blend mode, and a drop-down list menu of 25 blend mode commands will pop up. Select different blend mode commands to create different blend effects; the blend mode of the layer is used to control the upper and lower layers. When setting the blending effect, you also need to set the opacity of the layer. The blending mode options described below assume that the opacity is 100%.
Normal: This option allows the upper layer to completely cover the lower layer.
Dissolve: If the upper layer has soft off-transparent edges, select this to create a pixel-like effect.
Darken: The darker color of the two layers will remain as the blended color, pixels lighter than the blended color will be replaced, and pixels darker than the blended color will remain unchanged.
Multiply: The overall effect shows the image effect composed of the darker pixels in the pixel values of the upper layer and the lower layer. When any color overlaps with black, black will be produced. When any color overlaps with white, the color will remain unchanged.
Color deepening: Selecting this option will reduce the contrast of other areas except black in the upper layer, causing the contrast of the image to decrease, resulting in a shadow effect of the lower layer through the upper layer.
Linear Burn: The upper layer will be blended with the image based on the grayscale of the lower layer. This mode is not valid for white.
Dark: Based on the saturation of the upper layer image, then use the upper layer color to directly cover the dark area color in the lower layer.
Lighten: Make the darker areas of the upper layer transparent, making the image brighter through the lighter areas below.
Color Screening: This item is opposite to the effect of "Multiply". The overall effect shows the effect of combining the brighter pixels in the pixel values of the upper layer and the lower layer. The resulting image is a bleached color in the image. effect.
Color Dodge: Contrary to the "Color Burn" effect, "Color Dodge" uses the upper layer to increase the brightness according to the grayscale program of the lower layer, and then blends it with the lower layer. This mode can usually be used to create the center point of the light source. Extremely bright effect.
Linear dodge: Based on the color information of each color channel, lighten the base color of all channels and reflect the mixed color by reducing the brightness of other colors. This mode is invalid for black.
Light Color: This item has the opposite effect to "Dark Color". This item can directly cover the highlight area color in the lower layer with the color in the upper layer according to the saturation of the image.
Overlay: The final effect of this image is determined by the layer below. The highlights and shadows of the layer above will remain unchanged, but the midtones will be mixed in.
Soft Light: Lightens or darkens colors to give the image a very soft effect. Areas lighter than a neutral gray base will be brighter, and areas darker than a neutral gray base will be darker.
Strong Light: This item has a similar effect to "Soft Light", but its program is much larger than the "Soft Light" effect, and is suitable for adding strong light effects to images.
Brightness: Reduces contrast based on the grayscale of the blended color, making the image lighter or darker.
Linear light: Reduce or increase the brightness of the image according to the grayscale of the color of the instance, making the image brighter.
Point light: If the mixed color is lighter than 50% gray, the pixels with dark mixed color will be replaced without changing the pixels with bright mixed color; conversely, if the mixed color is darker than 50% gray, the bright mixed color will be replaced. pixels without changing the blend color of dark pixels.
Solid color mixing: According to the distribution of image colors in the upper and lower layers, the intersecting portion is filled with the intermediate value of the colors of the two layers. This mode can be used to create a color block effect with strong contrast.
Difference: The bright area of the upper layer inverts the color of the lower layer, and the dark area displays the color normally. The effect is completely opposite to the original image.
Exclude: Creates an effect similar to Difference mode but with less contrast. Mixing with white will invert the base color value, mixing with black will not change it.
Hue: An effect created by the hue of the blend color of the image above and the brightness and saturation of the layer below.
Saturation: An effect created by the brightness and hue of the image below and the saturation of the blend color of the layer above.
Color: An effect created by the brightness of the image below and the hue and saturation of the layer above. This preserves the grayscale in the image and is useful for colorizing monochrome images and colorizing color images
Luminance: Creates the opposite effect of Color mode, consisting of the hue and saturation values of the image below and the brightness of the image above.
Let's first take a look at where these blending modes exist
——1: “Layer Mixing”—between layers—visual changes between upper and lower layers
——2: “Apply Image”—between channels—this layer changes directly
——3: “Calculate” ——between channels—the upper and lower layers and this layer will not change, creating a new selection
A certain original picture, remember, when we get the picture, we must develop a good habit of observing first, so that we can start in a targeted manner. What do we observe????
We found that the texture and light of the white porcelain cup and bamboo tube are good, and basically do not need to be moved much, but the background is a bit dim, we just need to brighten the background a little and it will be fine!!!!
We have an idea!!!
Let’s take a look at the overall brightening effect first!
According to the method we used when we first learned, how do we do it??? Use the lasso tool to select the white porcelain cup and bamboo tube, then feather it, and then invert the selection, right???
In this way, the background is selected and the brightness of the background is improved. I guess many people are like this! I am the same way if you want me to do it. There is nothing right or wrong about it.
But why use this picture as an example?
We say we need to master a method, start with simplicity! We can take this picture and figure out the idea at a glance, bright area, normal, dark area, brighten, reflect details, okay, that's it.
We have learned about channels, understood channels, and know that channels are selections. Next, let’s see how calculation tools are applied to channels to generate selections.
