Color Management - Ice Cream Cream Cake
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Ice cream cakes are undoubtedly a huge temptation in the hot summer months.
Banknote problem
Like the ice cream cake, in the pursuit of accurate and unified color reproduction, color management is just like the cake in the cold drink house, attracting almost all printers. In the last chapter, we ate “cutely” (we seem to see color management as simple as this), but don't worry, this is just the beginning. In this paragraph you will find that color management is not so easy, except cute. We must also spend more money to achieve our color management. This is like the price we have to pay to get a cool cool in the hot summer.
What do we need to prepare for the issue of color management? IT8's color target, spectrophotometer (photometer for screen color management and color management for output is not the same), color management software.
It's not complicated to measure the IT8 spectrophotometer and screen colorimeter (small black instrument). These things can be obtained as long as you are willing to spend money. This is a price. Don't expect to get color without spending money. The possibility of management.
The establishment of PROFILE is actually not complicated.
This seems like a very cumbersome process, but don't forget, we have already got the IT8, spectrophotometer and color management software for color management. The next work will be simpler than we think. Much, the process is as if we have learned to use a knife and fork to enjoy it after buying an ice cream cake.
What is IT8?
The problem is simpler. It is the standard for a color we will use. It contains 928 standard patches. Color conversion between color and standby will use it as a bridge. --What does it mean?
Didn't we talk about it in the last chapter? The purpose of PROFILE is to establish a color representation relationship, that is, what kind of conversion relationship does the device's representation of color have with the standard we mentioned (CIE)? Through the measurement and calculation of IT8, we can get this relationship. Here IT8 is a known standard we need, or has been specified by us as the standard here.
What is IT8? It is the color standard with 928 standard color blocks. Since each IT8 color block already has a certain CIE value, we can measure the device's color reproduction of the IT8 to find a relationship between the device and the standard (CIE). Then this relationship is the PROFILE we have been doing.
Establishment process
We know what IT8 is, what it is for, and it's easy, so now let's start eating ice cream. Believe me, what I said below is like telling you how to use a knife and fork to taste ice cream as easy.
First of all, we have to measure the original of IT8 (although we have already determined that it is standard, but we still need to measure each color block to ensure that we know the value of each color block), a total of 928 color blocks, we To measure 928 times, is it troublesome?
Fortunately, we can use X-rite or Grinda's dedicated spectrophotometer (we call them the name of the beetle), the measurement of the IT8 is convenient, you only need to make a simple setting of the device, Then you can listen to the colorimeter such as music and measure it yourself. The result of this measurement will be directly input into the excel we have opened.
Then there is the copying of the device to the IT8 (the color management process of the display we don't discuss first, because it is a bit special), which can be a copy on a digital camera, scanner, digital proofing or even a printing press. Then there is a measurement of the copy result, and then we get a new set of data.
Next, we can input the data we have obtained to the software (of course, the copy image software of IT8 obtained by scanner or digital camera can measure itself, and the replica of digital proofing, digital color expansion, printing copy, etc., we Still need us to use the photometer measurement), then we make some general settings for these software, OK, we quickly got a PROFILE file we want, we will get different extension files for different software. Or ICC or ICM, but the same, almost all systems that support color management can make normal calls to these two files.
Let's take a look at the PROFILE formation process of the display, first start the color management software, then we press the software to set the display to the acceptable state of the software, such as brightness, color saturation, etc.; Tools for measuring the color of the display (such as Grinda's EYE-ONE), suck it onto the display, start the software and start measuring. The results of the measurement are calculated by the software, and we will easily get the PROFILE we need.
Screen color measurement
Structure of PROFILE
Like the creamy ice cream cake, we don't know the ingredients we can eat, and we also eat very fragrant. But can we learn more about its ingredients and eat more?
The ICC standard profile consists of a file header, a tag table, and tag element data.
The file header records the basic information of the color profile, which is 128 bytes long. Includes color profile size, category, version number, CMM type, chroma space type of data, color profile generation time, operating system platform, CMM and distribution processing tags, device manufacturer, device model, device characteristics, copy intent The XYZ value of the chromaticity space illuminator, the mark of the color profile generator, and the like.
The length of the tag table is 4+12*N bytes, where N is the number of tags. The first N bytes record the number of tags in the tag table, followed by the contents of each tag index, each tag index content is 12 bytes, respectively record the tag name (4 bytes), size (4 Byte), offset address (4 bytes).
The tag element data is used to provide complete information and data for color conversion by the color management module. The ICC color profile has dozens of tags, each of which has different definitions, uses, and byte lengths. The content and number of tags in different feature files are also different.
For those who are not professionally engaged in color management research, it is sufficient to do some simple understanding of the above. We don't need to know more about it at all. After all, we still have more work to do.
Call of PROFILE
First, the PROFILE is activated in the device and then called in the response software. For example, we can call the ICC of the display in the properties of the display, or call the printed ICC in PHOTOSHOP, or in the PAGEMAKE or Founder's typesetting software. Call, we can also call in the digital proofing system. This is not a complicated process. Since the different softwares are called differently, they are all simple enough to be used as long as they are called. I think since the ice cream cakes are all bought, let's eat them. The waiter will talk more about how you chew it. It must be embarrassing.
Standard! What is important is the standard
This standard is different from the CIE or IT8 we mentioned above, but it is equally important. We need a standard light source to observe the color. We need standard conditions for printing. We need to change all the changes without changing or with as few changes as possible. The process, so everything done by color management is not in vain.
For example, the printing pressure can be 0.1 mm or 0.15 mm. Different pressures will definitely lead to different results, and we can't have more energy to make different situations for all situations when we make PROFILE. PROFILE file. Even if we have enough time and energy, these messy PROFILEs are enough for us to have a headache.
When it comes to standards, it is something that everyone can accept, such as: the standard light source when viewing prints (D65 is the most ideal), the most ideal pressure and ink balance during printing, and the long-term standard use.
In this way, we will also find that true color management is not only the establishment of PROFILE, but also the adoption of standards for all devices and people involved in color display or reproduction. If PROFILE provides the possibility of color management, then the greater use of standards is the basis for color management.
In fact, color management is a big system.
If you want to complete the color management from the device to the software, I think the problem is far from being a "cute" or "ice cream cake". I am afraid I have an ice cream shop. Our two articles are aimed at The real details are also to be read by the reader in practice.
Let's review our color management process again:
Input (scanner, digital camera):
1. Measure the original of IT8
2. Input or output IT8 original
3. Place the input IT8 original into the color management software
4. Integrate the chromaticity value of the IT8 original and the input IT8 image in the software.
5. Make some general settings for the software
6. Get PROFILE
7. Called in the corresponding software of the device
Output (proofing, printing)
1. Standardize management of the process;
2. Measure the data of the IT8 original;
3. Copy IT8 (such as digital camera, we also need a standard light box, input in the light box)
4. Measure the copied IT8
5. Enter the two sets of data into the software for calculation (the software automatically completes the calculation process)
6. Get PROFILE
7. Called in the corresponding software of the device
Display
1. Open the management software
2. Adjust the display
3. Place the monitor color measurement equipment
4. Get the PROFILE file
5. Called in the display properties