A: The black version will have different types due to different color separation settings: None, Light, Medium, heavy, Maxium, etc. It means that the color of the black and gray areas on the image can be divided into no-black version, light black version, medium black version, heavy black version, and all black versions. So why can black or gray be divided into black dots of different sizes?
We know that the pure black version can represent the gray series of colors, the yellow, magenta, and cyan primary colors can also represent the gray series of colors, and the yellow, magenta, cyan, and black colors can also represent the gray series of colors.
If the neutral gray color is completely represented by yellow, magenta, and cyan, then the Internet access point of the black version is 0%, and the black version is None;
If the neutral gray color is represented by a pure black version, it is a Maxium type black version;
If the neutral colors are represented by the four colors of yellow, magenta, cyan, and black, the dots of the black version are larger, and the dots of yellow, magenta, and cyan are smaller. When the black version has a smaller Internet access point, the yellow, magenta, and cyan sites are larger, forming a relationship with each other. Then there will be black versions of Light, Medium, and Heavy. For example, the color R163G163B163 can be separated according to the following conditions:
When the black version is Light, the separation result is C40% M33% Y33% K1%; when the black version is Medium, the separation result is C37% M30% Y30% K7%; when the black version is Heavy, the separation result is C26 % M20% Y20% K22%;
It can be seen that there is still a big difference between their color separation results, but the printing results should be similar.
The above is about the color separation result for neutral gray color. In fact, the black version type will also have different effects on the compound color in the image, because the compound color contains the gray component, and the gray component also has how to allocate yellow, The ratio of magenta, cyan and black. Such as brown red R186G139B10, the color separation results are:
When the black version is Light, C33% M39% Y100% K13%; when the black version is Medium, C26% M31% Y99% K23%; when the black version is Heavy, C70% M24% Y99% K32%.
What is a separation table? What does it do?
Answer: The color separation table is actually the sum of various settings during color separation. As shown in Figure 1, it includes Ink color (ink color type), Dot Gain (dot expansion value), separation type (Separation Type), black version type (Black Generation), black version dot maximum (Black Ink Limit), total Setting of parameters such as Total Ink Limit. This is a feature of Photoshop's flexibility and pertinence in color separation. It works when the RGB color mode is converted to CMYK mode, that is, color separation, and their different settings will produce different color separation effects. After Photoshop5.0, the color separation table has been made under the color management settings of the CMYK color mode, becoming a part of color management.
What does ink color setting mean? Why do you need to set the ink color?
Answer: There are many ink types in the ink color type setting drop-down menu (in fact, the options are printed on different substrates). See Ink Color in Figure 1. There are actually two meanings here, namely the choice of the type of ink used in printing and the type of printing paper. Here Toyo Inks refers to Japan Toyo Ink; Eurostandard refers to the European standard ink color; SWOP refers to the web offset printing standard ink color; Tektronix phaser III Pxl refers to the Tektronix printer ink color. Coated refers to coated paper (such as coated paper), Uncoated refers to uncoated paper (offset paper), and Newsprint refers to newsprint. Therefore, the Ink Color option is actually to choose the color that the ink you use when printing on the substrate used. Because our domestic inks do not have corresponding options in the menu here, in actual operation, such as printing on coated paper, it is recommended that you use Toyo (Coated) or SWOP (Coated); if printing on offset paper, you can choose Toyo (Uncoated ) Or SWOP (Uncoated).
So why set the ink? This is because the choice here is different, the results of color separation will also be different, that is, the ink you choose is similar to the ink you use, to ensure that the color can be accurately restored when printing. In addition, because the same ink will have different printing colors on different papers, choose the ink color on the same paper as you printed to ensure the correct color separation results.
How appropriate is the setting of Dot Gain at the color separation table?
Answer: The dot expansion is the phenomenon of dot increase caused by the printing pressure and the penetration of ink on the substrate during the printing process. This phenomenon is proven to exist. The size of the dot expansion value is affected by factors such as printing pressure, substrate, and ink viscosity; generally, the larger the printing pressure, the larger the dot expansion; the stronger the substrate absorption, the larger the dot expansion value. Specifically, newsprint, offset paper, and coated paper have the largest value-added newsprint, and coated paper are the smallest. For the dots of different sizes, the dot expansion value is different. Generally, the high-key and dark-tone dot expansion values ​​are smaller, and the mid-tone dot expansion values ​​are larger.
Dot Gain is set in the color separation table to pre-compensate for the dot expansion phenomenon in printing. That is, the dots are appropriately reduced during color separation, and the desired size is obtained after the dots are expanded during printing.
So how appropriate is the setting to increase the outlet? The simple method is mainly to set the maximum value of the dot expansion, and Photoshop will compensate the dots of each tone according to this value. If it is set according to the curve, the dot expansion value of each order under the actual printing conditions can be measured, and a curve is generated, and the dot expansion is compensated according to the curve. This compensation is more accurate. In actual work, it is still a more difficult task to determine the dot expansion value. In general, it is recommended to use the default setting of Dot Gain in Photoshop. For example, the default value when printing on coated paper is about 17%, the default value when printing on offset paper is about 22%, and the default value when printing on newsprint is about 30%.
When to choose GCR when separating colors? When to choose UCR? What is the difference between GCR and UCR color separation results?
Using GCR is easy to maintain the gray balance, reduce the total amount of ink overprinting during printing, make the ink dry faster, and improve the printing speed. For general images, GCR is generally used for color separation in Photoshop. UCR means background color removal, and its main target is for the darker complex colors in the image, and black K is used to replace the gray components in these colors. However, the scope of UCR is smaller than that of GCR. GCR has a wide range of effects, generally starting from the range of 20% gray scale, while UCR generally only works in dark tones. Therefore, for images with high color and rich dark tone in high school, UCR can be selected during color separation.
The difference between the two is that the black version of the GCR color separation is more and the tone is longer; and the black version of the color separation by UCR is less, but the K value is greater in the deepest place.
What does Gray Ramp mean?
Answer: The curve in the figure actually shows the color separation result for neutral gray, it can also be said to be a color separation curve, and it can also be said to be a gray balance curve. The neutral gray color separation result at point A in Figure 2 is called C50% M40% Y38% K12%.
What does Black Ink Lmit mean? what's the effect?
Answer: The maximum value of black ink refers to the maximum value of the percentage of black dots generated on the black plate during color separation. It can control the dot size of the black version during color separation, so as not to make the color too dull during color separation. At this time, the size of the input value has a defining effect. For example, when the color of Black Ink Lmit is 100%, the result is C80% M69% Y63% K68%, and the result of Black Ink Lmit is 70% is C89% M29% Y83% K51%. It can be seen from the data that the size of this value will directly affect the color separation results, but the color will not change much. As shown in Figure 3, it can be clearly seen from the color separation curve that Black Ink Lmit is 100% and 70% respectively.
What does Total Ink Lmit mean?
Answer: Here, Total Ink Lmit refers to the maximum amount of ink overprinting in four-color printing, that is, the actual amount of overprinting when the four-color solids of Y, M, C, and K (100% dots) are overprinted. If the ink is completely overprinted on the ink layer of the first color printing, its overprinting rate will not be 100%, generally less than 100%, so when the four-color solid overprinting, its total overprinting is between 320% and 360%. Therefore, it is recommended in Photoshop that Total Ink Lmit is generally set between 320% and 360%. The color separation curves at the set values ​​of 320% and 400% are shown in Figure 4. The color separation results of the same color R59G66B43 are: when the total ink volume is 320%, C67% M48% Y81% K56%; when the total ink volume is 400%, C67% M48% Y81% K56%.
What does CMYK Setup in Photoshop 5.0 or later mean? What is better for CMYK model?
A: Before Photoshop 4.0, there is a special option for Separation Table setting, which can be opened under File \ Color Settings. After Photoshop 5.0, it will be changed to File \ Color Setting \ CMYK Setup. It is recommended to use the Built In button. Because the flexible setting can be adopted at this time, the color separation conditions can be the same as the actual printing conditions. All the settings below are similar to the Separate Table and Printing Inks Setup in Photoshop 4.0 and earlier versions.
There is black text on a scanned RGB mode color manuscript. If you want to use the scanned words directly, what color is best for separating these words? How to achieve this ideal requirement?
Answer: For the black text and lines on the color image in RGB mode, it is better to separate the dots on the black version to form monochromatic text during color separation and adjustment. %. Because, if it is composed of four colors C, M, Y, K black text, if there is a bit of misalignment during overprinting, ghosting or colored edges will appear.
There is an easy way to achieve your goal: choose the type of the black version as Maximum in the color separation setting. At this time, all the black or the gray of the multi-color part is separated into only dots on the black version, which can be achieved when RGB → CMYK is executed. For example, a black R15G14B14 is separated into C0% M0% Y0% K95%, and if the black version type is Light in the color separation setting, the color separation result is C79% M78% Y73% K76%.
When is it better to change the image from RGB mode to CMYK mode?
Answer: Due to the small storage space and memory occupied by RGB images, the processing speed is faster during adjustment. Therefore, the emphasis on the sharpness of the image and the removal of noise are better in RGB mode. Therefore, it is recommended to fix the dirty spots of the image first when adjusting the image, and then convert it to CMYK after the sharpness is processed. Then proceed with color processing. Because even if the color is processed in the RGB mode, the color will still change slightly after being converted to CMYK.
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