Act profile is stately. Comparison of GCR and UCR - color separations in Adobe Photoshop. See what "ACT" is in other dictionaries

Evgeny Kuznetsov,

S> UCR is an image drawn with three colors of CMY, S> with shadows underlined with black paint. S> GCR -- an image drawn with black paint S> and decorated with three CMY colors. Quote from the printing forum

I would not simplify like that, and, for my part, I will try to bring some clarity to this issue.

Firstly, both GCR and UCR in performance Adobe Photoshop- just different sides of the same process - color separations, respectively, they work somewhat similarly, although they achieve (depending on the current settings) different results.

First, about the terminology, and, in particular, I will give a decoding of the abbreviations UCR and GCR.

UCR(Under color removal) in the general case, it really deals with the partial replacement of process colors with one black paint. This is done in the shadow areas of the image: where there is a sufficiently large percentage of the total ink content. De facto, at the output of a color-separated image, we get "VERY SKELETAL BLACK", which is contained only in deep shadows, forming, as it were, the skeleton of the image, its contour, emphasizing deep shadows (hence the name).

GCR(GRAY COMPONENT REPLACEMENT) also really replaces process inks in proportions that meet the gray balance conditions for a given triad color (according to the type of inks accepted by the "Printing inks" option) with one SUBSTITUTE black ink. In fact, the GCR color separation algorithm in Adobe Photoshop is similar to UCR, the only thing is the nuances of the settings of the other options available in CMYK Setup - Custom CMYK. De facto, at the output of a color-separated image, when using the GCR / Light or Medium color separation algorithm, we get a "skeletal" black color in the corresponding black channel. Depending on the Black generation settings, we can also get black, which is contained not only in deep shadows, but also in lighter areas of the image (for example, in 3/4-tones or midtones of the image).

That is, in the notation of Adobe Photoshop GCR and UCR are identical, the point is the possibility of settings. In fact, by combining color separation parameters or by manipulating the black generation curve while in GCR mode, we can achieve the result that is obtained when using UCR color separation.

Now - more about the differences between these modes. Everyone probably paid attention to the fact that when choosing the GCR color separation type, several more options become available (in particular, black generation - "Black generation" and "UCA amount"), and when choosing UCR, they become inactive. This is actually the point - UCR is actually a special case of GCR color separation, in which the Black Generation and UCA options are not relevant.
In any case, choosing GCR color separation, we simultaneously choose one or another level of black ink generation (Black generation) in the range from None to Maximum. This determines how dark the image must be so that instead of the triad, or in addition to it, black paint appears. For example, Black generation - Light determines that black ink will appear if the content of the so-called "staining (contaminating) component" in the main color built with process inks is at least 40%. This, for example, can be 40% Yellow in the 100C + 100M binary, or 40% Cyan in the 100% Magenta + 100% Yellow binary. That is, below these 40% (for example, in the case of 30% yellow content in the 100Cyan + 100Magenta binary), black ink will not be generated instead of the triad, higher it will. In fact, some "threshold" of the color separation algorithm is determined, and our task is to determine the threshold for this operation.

Just in case, here are the values of these "thresholds":

Light - 40% and above;

Medium - 20% and above;

Heavy - 10% and above;

Maximum 0% and above; in this case, black ink will replace even one-percent "dirty" additions to the main color throughout the image.

Fig.1. Color separation modes in Adobe Photoshop and their corresponding black ink generation curves

By the way, all these percentages can always be "peeped" in the same Adobe Photoshop, taking any level of black ink generation as a basis, and then selecting the "Custom" option in the same place.
From the user's point of view, Light provides the most triad and the least black, while Maximum provides the exact opposite - minimum triad and maximum black. From the point of view of the color corrector, the Light mode will give the largest color gamut, and Maximum (and Black Generation values \u200b\u200bclose to it: for example, Heavy) will produce some narrowing of the gamut. And from the point of view of the printer, it will be most difficult to maintain a gray balance when printing images "divided" in CMYK using Black generation: Light than images that have been color-separated, for example, with Black Generation: Heavy, since in the first case in There will be more than a triad in the neutral gray areas of the images, and any print density/dot gain fluctuations will cause the image to go out of balance.

UCR also provides for setting some levels of black generation, but they are not CLEARLY set - in fact, UCR is closest to the GCR / Light color separation, as it provides a large amount of triad and a small amount of black ink (and, as a result - maximum coverage of colors - minimum stability gray balance). With the difference that in GCR/Light the "activation level" is 40%, and in UCR it is about 60%. That is, it turns out not just "skeletal", but "very skeletal" black.

For the same reason, when choosing UCR, the UCA Amount option becomes unavailable. As you know, the UCA parameter ("Under color addition" or "Under color adjustment" - I have seen both versions of this abbreviation) controls the addition of process colors in the proportions of the "current" gray balance to the shadow areas of the image.
As a rule, UCA is used to maintain the density of those shadows that, as a result of strong subtraction (which happens with GCR/Heavy and GCR/Maximum), turned out to be too gray and, accordingly, not dense enough. Since UCR generates black at an even lower level than GCR/Light (and, accordingly, less subtraction from under black), the UCA option becomes unnecessary when using it.
Once again, I want to clarify that all of the above is relevant for the Custom CMYK menu in the environment of modern versions of Photoshop, and to a greater or lesser extent reflects the characteristics of the corresponding color separation modes in other applications, but does not reflect all possible cases of image color separation control. Therefore, Adobe Photoshop should not be considered as an ideal tool for creating ICC profiles and, accordingly, a tool that allows you to override all color separation parameters. For complete description this process in Photoshop lacks options such as Black start And Black Width, which exist in other, more advanced tools for creating ICC profiles (see Fig. 2.).

Fig.2. An example of describing options for managing black generation parameters in the GretagMacbeth ProfileMaker 5.x environment
For my part, I thank Alexander Pylsky for the constructive criticism expressed when writing this article.

The article was useful, and you would like to receive Additional information? We invite you to study at our The educational center. We conduct high-quality courses and trainings for color correctors, designers, prepress specialists, printing and advertising managers, and other professionals in the printing professions. Professional trainings with visits to students in Kyiv, Ukraine, or throughout the CIS and beyond.

Functions

ACT Inc. reports that the ACT measures a student's general knowledge of entering high school and the ability to complete college-level assignments through tests in different areas: English, math, reading, and various sciences. The optional written test shows the ability to correctly build your speech and write short essays. Core ACT scores can provide an indicator of college readiness, and scores on each of the optional tests show a basic level of in English, algebra, social sciences, humanities or biology.

Usage

The ACT is most commonly taken by students from the Midwest and southern states, while SAT is more popular on the eastern (although ACT has previously prevailed there) and western coasts of the United States. The use of ACT scores by educational institutions has increased as a result of a large number criticism of a competitor. The Mensa Society and the High IQ society also accept ACT scores (until September and at least 29 points) upon entry into the society. The Trinity Nine Society accepts scores from 32 on the exam before October 1989, and a score above 34 on the exam later.

Structure

For the most part, the ACT consists of four-choice questions. Subject Tests: English, Mathematics, Reading and Scientific Thinking. Each subject test is scored on a scale of 1 to 36 points. English, Maths and Reading tests also have additional scores from 1 to 18 (they are not related in any way to general assessment for the subject test). The “total score” is the sum of all four tests. Additionally, you can take a written test, which is assessed on a scale from 2 to 12 points, the combined result of the written test and the test of English language varies from 1 to 36. From one to four comments to the essay from the reviewers can also be attached. Written test for overall result does not affect.

For each correct answer, one point is awarded to the "temporary score", for incorrect answers, unlike SAT, points are not removed. To improve the test results, the student can retake it, according to statistics, 55% of those who retake the ACT improved their result, 22% remained the same, and 23% passed worse than before.

English

The 75-question test contains 5 text passages with some underlined sentences on one page and instructions to correct the underlined parts on another. One part of the questions focuses on text formatting and punctuation - commas, apostrophes, colons, etc. The other part tests rhetorical skills - style (clarity and brevity) and text organization. The test lasts 45 minutes.

Mathematics

Consists of 60 test questions, of which:

14 assess the basic knowledge of mathematics
10 - elementary algebra
9 - intermediate level of algebra
4 - elementary trigonometry

Calculators are allowed, but, unlike the SAT, programmed ones are prohibited. The test lasts 1 hour, in the ACT it is the only one given tests with five answer options instead of four.

Reading

Consists of 40 comprehension questions on four presented passages (taken from books and magazines):

The first is part literary work(short works and novels)
The second concerns the social (history, economics, psychology, political science and anthropology) sciences
The third affects the humanities (art, architecture, dance) sciences
The fourth refers to the natural (biology, chemistry, physics) sciences

The test lasts 35 minutes.

Scientific reflection

Scientific Thinking - 35 minute test with 40 questions. Questions test the ability to interpret, analyze, evaluate, reason, and solve problems. 7 passages are given scientific texts(in biology, geography, chemistry and physics). Almost all passages are taken from scientific research, but one of them is the opposite points of view of several different scientists on a phenomenon. For each passage where the material is sometimes difficult to understand, 5-7 simple questions are attached. IN general test has three directions:

Written test

The written test is always taken at the end of the exam and lasts 30 minutes. All essays should be on a specific topic, usually social. The written test does not affect the overall result. Instead, a joint English test/Writing test result is created. If a student writes an essay poorly, then this mixed score will drop by a maximum of 2 units. The specific structure of the essay is not defined.

Two trained employees evaluate the work from 1 to 6 points, "0" is put in the case when the essay is not written, not in English, not written with a No. 2 pencil, or it is impossible to make out what was written. Final result is the sum of the two scores. If the scores of two inspectors differ by more than one point, then a third one is appointed, which will determine the final result.

Although this test is optional, many educational establishments request it for admission and the grade for the essay may affect the admission decision.

results

Average total score The ACT is 18 points with a standard deviation of 6 points in both directions, but this statistic changes from year to year.

Below is a table of average results for 2009.

Passing the test

Notes

Wikimedia Foundation. 2010 .

See what "ACT" is in other dictionaries:

ACT-R- (pronounced act ARE: Adaptive Control of Thought Rational) is a cognitive architecture mainly developed by John Robert Anderson at Carnegie Mellon University. Like any cognitive architecture, ACT R aims to define the basic and irreducible… … Wikipedia

ACT!- Entwickler Sage Betriebssystem Microsoft Windows Category CRM Software Lizenz proprietär ... Deutsch Wikipedia

act-up

act-up- Paris Date de création 1989 Réunion hebdomadaire tous les jeudis à 19 h à l École des Beaux Arts 14, rue Bonaparte 75006 Paris Nombre d adhérents 150 revendiqués Site internet … Wikipédia en Français

act up- Paris Date de création 1989 Réunion hebdomadaire tous les jeudis à 19 h à l École des Beaux Arts 14, rue Bonaparte 75006 Paris Nombre d adhérents 150 revendiqués Site internet … Wikipédia en Français

act- 1 n 1 a: something done by a person in accordance with his or her free will a tortious act see also actus reus b: the failure to do something that one has a legal duty to do – called also negative act; 2 a … Law dictionary

There was an opportunity to optionally take a written test (a month later, a similar section appeared in the SAT). All four-year colleges and universities accept ACT scores, but some may also require additional performance information.

Functions

ACT Inc. reports that the ACT measures a student's general knowledge of entering high school and the ability to complete college-level assignments through tests in different areas: English, math, reading, and science. The optional written test shows the ability to correctly build your speech and write short essays. Core ACT scores can provide an indicator of college readiness, and scores on each of the optional tests show a foundation level in English, Algebra, Social Studies, Humanities, or Biology.

Usage

The ACT is most commonly taken by students from the Midwestern and Southern states, while the SAT is more popular in the eastern (although ACT was prevalent there) and west coasts of the United States. The use of ACT scores by educational institutions has increased as a result of much criticism of the competitor. Mensa Society, organization for people with a high IQ, also accepts ACT results (until September and not less than 29 points) when joining the society. The Trinity Nine Society accepts scores from 32 on the exam before October 1989, and a score above 34 on the exam later.

Structure

For the most part, the ACT consists of four-choice questions. Subject Tests: English, Mathematics, Reading and Scientific Thinking. Each subject test is scored on a scale of 1 to 36 points. The English, Math, and Reading tests also have additional scores from 1 to 18 (they have nothing to do with the overall score for the subject test). The “total score” is the sum of all four tests. Additionally, you can take a written test, which is assessed on a scale of 2 to 12 points, the combined result of the written test and the English language test varies from 1 to 36. One to four comments on the essay from the reviewers can also be attached. The written test does not affect the overall result.

For each correct answer, one point is awarded to the “temporary account”, points are not removed for incorrect answers. To improve the test results, the student can retake it, according to statistics, 55% of those who retake the ACT improved their result, 22% remained the same, and 23% passed worse than before.

English

The test of 75 questions contains 5 passages of texts with some underlined sentences on one page and indications of the underlined parts on the other. One part of the questions focuses on text formatting and punctuation - commas, apostrophes, colons, etc. The other part tests rhetorical skills - style (clarity and brevity) and text organization. The test lasts 45 minutes.

Mathematics

Consists of 60 test questions, of which:

14 assess the basic knowledge of mathematics
10 - elementary algebra
9 - intermediate level of algebra
4 - elementary trigonometry

Calculators are allowed, but, unlike the SAT, programmed ones are prohibited. The test lasts 1 hour, in the ACT it is the only one given tests with five answer options instead of four.

Reading

Consists of 40 comprehension questions on four presented passages (taken from books and magazines):

The first is a part of a literary work (short works and short stories)
The second concerns the social (history, economics, psychology, political science and anthropology) sciences
The third affects the humanities (art, architecture, dance) sciences
The fourth refers to the natural (biology, chemistry, physics) sciences

The test lasts 35 minutes.

Scientific reflection

Scientific Thinking - 35 minute test with 40 questions. Questions test the ability to interpret, analyze, evaluate, reason, and solve problems. 7 excerpts of scientific texts are given (on biology, geography, chemistry and physics). Almost all of the passages are taken from scientific research, but one of them is the opposing views of several different scientists on a phenomenon. For each passage where the material is sometimes difficult to understand, 5-7 simple questions are attached. In general, the test has three directions:

Written test

Two trained employees evaluate the work from 1 to 6 points, "0" is put in the case when the essay is not written, not in English, not written with a No. 2 pencil, or it is impossible to make out what was written. The final result is the sum of the two scores. If the scores of two inspectors differ by more than one point, then a third one is appointed, which will determine the final result.

Although this test is optional, many institutions require it for admission and the grade for the essay may affect the admission decision.