Photoshop is an in-depth analysis of beauty color (Author: zhangwei Source: Silicon Valley Power)

What is 305911? It is a mathematical expression, that is, 0.3R 0.59G 0.11B. In photoshop, what exactly is it a mathematical expression to calculate? Some people say it is the brightness in the lab; others say it is the grayscale in the grayscale mode; others say it is the brightness in the RGB mode (that is, the brightness in the histogram). This does not mean much for the operator to study it. The operation of the image has more subjective components. But for researchers, it is necessary to find out what it is. The formula itself is just a fixed definition, nothing needs special explanation. The following is just a verification method to explain whether it should be classified as lightness, grayscale or brightness. Before verifying its ownership, first concrete the expression 0.3R 0.59G 0.11B into an image and calculate it. Do some preparation work first. Copy the red, green, and blue channels to the layer.

Convert 0.3R into a color scale value, 0.3×255=76.5, take Rounded to 77. Then operate as shown.

Merge layers and close. Convert 0.59G into color scale, 0.59×255=150.45, rounded to 150. Then operate as shown.

Merge layers and close. Convert 0.11B into color scale, 0.11×255=28.05, rounded to 28. Then operate as shown.

Then change the layer blending mode of the red channel layer and green channel layer to ” Linear Dodge”. Linear dodge is addition, adding the values of the same pixel on three layers together.

Merge the three channel layers. I changed its name to: 0.3r0.59g0.11b. This 0.3r0.59g0.11b layer is what we call the mathematical expression above. The preparation work is now complete, let’s proceed to verification.

Verification:

Open the histogram and change “Channel” to “brightness”. Pay attention to the histogram and the set of data with a red box below it.

Close the eyes of the previous layer and change the “Channel” to “Brightness”. Pay attention to the histogram and the set of data with a red box below it. And compare with the histogram from upstairs. It can be seen that they are basically the same, and the small discrepancies in the data are calculation errors.

Close the eyes of the previous layer and change the “Channel” to “Brightness” “. Pay attention to the histogram and the set of data with a red box below it. And compare with the histogram from upstairs. It can be seen that they are basically the same, and the small discrepancies in the data are calculation errors.

Close the eyes of the previous layer, close the eyes of the upper image, use Calculate the data on the information panel: 0.3×238+0.59×190+0.11×144=199.34, rounded to 199.

Let’s convert the image to Lab mode. The upper layer is no longer needed, close or delete it. Open the histogram to see the brightness of the underlying layer. Pay attention to the histogram and data, and compare it with the histogram and data on the 10th floor. You can see that there is a big difference, which cannot be explained by errors.

Click on the brightness channel in the channel panel and see that the data of the set color point is 216, which is obviously not equal to the formula 0.3 R 0.59G 0.11B Calculated value 199.34.

Compare the brightness map of lab with the brightness map of rgb, the difference is obvious. Therefore, 0.3R 0.59G 0.11B should be the brightness calculation formula in RGB mode rather than the brightness calculation formula in lab mode. I once asked the moderator Feng Xi for advice. The calculation formula for brightness is very complicated, so I won’t mention it here.

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