Need some advice on PS color management, urgent, urgent, urgent

Some discussions on issues related to color management (reposted)

Question 1: What kind of monitors require calibration by professional instruments?

Answer 1: Advertising, design, printing, printing, animation and other fields require true color restoration; stable monitors require color adjustment with professional instruments. Any monitor, regardless of price; brand, even the same model; monitors produced in the same batch have different indicators. Low-end monitors such as ViewSonic; Samsung, etc., and high-end monitors such as EIZO; Apple, etc. In addition to the fineness of the display and good restoration ability, there is only stability. High-priced monitors will be relatively more stable. Actual measurement data shows that after the EIZO monitor is calibrated once, if the working environment does not For major changes, you do not need to frequently perform color calibration on the monitor. However, low-priced monitors such as ViewSonic still need to perform frequent calibration on the monitor even when the working environment does not change significantly. This is due to the stable performance of low-end monitors. It’s not very good. We know that there are many factors that affect the change of the display, such as: magnetic field interference; changes in ambient light sources, etc. The display is changing at any time, but high-end displays will eliminate interference factors to a large extent and slow down the display. The speed of change.

Question 2: How often does the monitor need to be calibrated?

Answer 2: When the light source of the working environment does not change significantly; when the placement of the monitor does not change significantly; when the computer graphics card connected to the monitor does not change, we need to do a monitor inspection once a week or so. Color adjustment. Unless the light source of the working environment has changed greatly, we can rely on visual inspection. Small changes can only be observed through professional instruments such as I1 (EYE-ONE). Theoretically, as long as the color temperature of the light source in the entire working environment does not change, We should be able to accept a change of plus or minus 300K, but one thing to note is that when measuring the color temperature of the light source in the working environment, you must avoid interference from outdoor stray light, because the outdoor color temperature changes greatly throughout the day. I believe everyone understands this.

Question 3: Does having a calibrated monitor mean that what you see is what you get?

Answer 3: Not so! In order to achieve the same effect between what is seen on the screen and the actual output, it is not enough to calibrate the monitor alone, or only part of the work is completed. What you see is what you get is actually the central concept of color management, that is: the real thing-- -Display image---Output finished product (silver salt; printing) The three are relatively consistent in terms of color, which requires us to separately check the source equipment (digital camera; scanner, etc.); monitor; output equipment (enlarger; printing machine) machine; printer) to make color adjustments.

Question 4: After the monitor is calibrated, the colors feel very dull and not as bright as before. Is there something wrong with the monitor adjustment?

Answer 4: It is normal for the display’s color saturation and brightness after calibration to be as gorgeous as before adjustment, because the purpose of adjusting the display is to adjust the color space of the display to any output device. Within an acceptable range (international IT8 standard), so that the colors will be close when the finished product is actually output. We know that color monitors can display 16.7 million colors, but our printing presses or printers can display only 16.7 million colors. Far less rich than a monitor.

Question 5: Are CRT monitors necessarily better than LCD monitors?

Answer 5: Not necessarily, CRT (Cathode Ray Tube) is a cathode ray tube. It is a display technology that is widely used.

LCD is the abbreviation of Liquid Crystal Display in English, that is, liquid crystal display. It is a digital display technology that can filter light sources through liquid crystals and color filters to produce images on a flat panel. Compared with traditional cathode ray tubes (CRT), LCDs take up less space, have low power consumption, low radiation, no flicker, and reduce visual fatigue. Disadvantages: More expensive than CRTs of the same size. Many people think that compared to CRT monitors, the image quality of LCD monitors is still not perfect, which is mainly reflected in bright colors and saturation. However, at present, the indicators of many models of EIZO have reached or exceeded CRT monitors of the same price range. , such as EIZO’s CG series. Another point is that CRT monitors are more susceptible to interference from external magnetic fields than LCD monitors, which affects the color effect of imaging. Many CRT monitors will become magnetized at the four corners of the monitor after being used for a period of time.

Question 6: Can Apple monitors be adjusted to the same color standard as PC monitors?

Answer 6: Yes, we know that the display gamma standard of PC computers is 2.2, while the gamma standard of Apple monitors is 1.8. Many people ask me which one is the real gamma standard. Today I can tell you , the gamma standard is actually 2.2, because experiments have proven that the gamma (contrast coefficient) that our human eyes can recognize is 2.2, which means that only when the gamma of the display is adjusted to 2.2 can it be close to the color contrast seen by our human eyes.

Question 7: Can the color management instrument adjust multiple monitors to a consistent state?

Answer 7: It is almost impossible to achieve a completely consistent state. Many monitor manufacturers claim that they can adjust multiple monitors to a unified state, but do not clearly specify the different brands and models of monitors. Is it possible? I once did an experiment in Hubei. I used high-end monitor calibration equipment to adjust 20 ViewSonic monitors at the same time. The results obtained were different, because even monitors of the same brand model and produced at the same time may not have the same accuracy. will have the same color perception, because there are many factors in the image, we can only be the closest. High-end monitors are more similar, and low-end monitors are much different. I once used 4 brands at the same time; 6 brands A total of 15 monitors of the model *** were adjusted to a basically consistent state through the monitor adjustment instrument, but it has no actual value. This is because all 15 monitors have different degrees of attenuation, so they can be adjusted to a relatively uniform state. The reason is that I took the worst indicator among the 15 monitors as the standard, and the other 14 monitors moved closer to it. Although the results were uniform, they directly affected the color expression of the other 14 monitors, which is not advisable. In fact, as long as each monitor is measured according to the adjusted standards, they will all move closer to the international color standards. In other words, their color performance will be closer.

Question 8: Does the monitor need a hood for use?

Answer 8: Definitely necessary! Some friends think that it is not very convenient to use the monitor after adding a hood, so they simply do not need a hood. This is wrong. We know that the monitor is a luminous body, so external light sources have great interference with our ability to identify the correct monitor color. Function, for example, when the color temperature of the external light source reaches 6500K, but our monitor is only 5500K, then when the external light source shines on the monitor, we will find that the color of the monitor has changed. A good hood can greatly reduce the color interference of external stray light on the display. The hoods currently on the market are relatively expensive, most costing hundreds of yuan each. Some friends may ask why they are so expensive. In fact, at this time Due to the raw materials used to make the hood, most of the materials used to make the hood are pure black and have strong anti-reflective properties.

Question 9: Can ICC files of the same brand and model be used interchangeably?

Answer 9: No! ICC files are directional and unique and cannot be mixed.

Question 10: How long does it take for the monitor to be calibrated after it is turned on?

Answer 10: Generally speaking, the monitor can be calibrated half an hour after it is turned on, because all indicators of the monitor tend to be stable at this time, which is suitable for calibration work. The EIZO monitor should be calibrated within 3 hours after it is turned on. Calibration can be carried out after a few minutes.

Question 11: Why is it that when I use the same instrument to calibrate the same CRT monitor, the results are not as good as those calibrated by others?

Answer 11: This may be because you adjusted the monitor menu too quickly when calibrating the monitor. We know that for CRT monitors, any operation on it, such as adjusting brightness; contrast, etc., is performed by It is determined by the temperature of the picture tube. Sometimes we adjust the speed too fast and enter the next state before the picture tube responds. Of course, we cannot get the best effect of monitor calibration. We need to develop a good state, that is, when you When calibrating a CRT monitor, do not adjust the monitor too quickly. After each adjustment, wait at least 5 seconds before fine-tuning until the next step.

Question 12: I want to adjust the display of my laptop to a standard color state. Can I do it?

Answer 12: It depends on the configuration of your laptop. It must have an independent graphics card. For example, the ATI MOBILITY RADEON series, the graphics card level is naturally higher. Of course, the graphics card of a laptop is basically There is nothing too low-level.

Question 13: How to use the monitor ICC file?

Answer 13: The display device characteristics file is what we usually refer to as the monitor icc file. icc is actually the abbreviation of "International Color Consortium" (The International Color Consortium). The icc file of the monitor is a file that supports RGB. It can be called by the system as the monitor's configuration file. The method of using the monitor's ICC file is very simple. Right-click the mouse on the desktop of the computer to enter "Properties", and in "Properties" select "Settings" - "Advanced" - " Color Management" to select or see the ICC file of the monitor.

Question 14: Will the dead pixels on the monitor affect the color accuracy?

Answer 14: Generally speaking, no. When any monitor leaves the factory, the number of dead pixels is within the normal range as long as it does not exceed 3. However, if there are obvious lines on the monitor, it will affect the performance of the monitor. The color of the monitor is gone.

Question 15: What should you pay attention to when the output device produces ICC files?

Answer 15: If you want to generate an ICC file for an output device, preliminary work is very important. If it is a digital printing output machine using silver salt technology, we must first determine whether its printing solution meets the standard (configuration ratio; The temperature of the liquid; the replenishment amount of the liquid; the circulation ability of the liquid). If it is an inkjet printing or printing machine, we need to determine the quality source of the ink and the quality of the consumable paper, such as the amount of ink. The biggest difference between the silver salt process and the printing process is that the working spaces of the two are different. Silver salt is RGB and printing is CMYK. Once the above points are determined, we only need to control the color block of the print output device. At this time, just turn off all source color settings of the machine. When scanning color block files, pay attention to continuity, and avoid color management instruments from mixing other colors with their laser light sources when scanning.

Question 16: Does the ICC file generated by the output device with more color blocks in the color block file be the most perfect?

Answer 16: Not necessarily. Many people have asked me the same question. We have conducted experiments many times and proved that as long as 918 color patches are used, it is enough to express the color gamut space of any output device. . We have produced more than 9,000-point color block files on the Italian POLI machine with silver salt technology; the American ZBE darkroom amplification equipment; Norishi 32/33/24 series; Tailai; zhetha series and other models, and the effect is the same as 918 There is no obvious advantage compared with color blocks. Our experimental results on KD2100; HP INDIGO5000 and other printing machines are also the same.

Question 17: The output device ICC file we created does not work well when applied to the original image file, and there are color spots. What is the problem?

Answer 17: First of all, we need to rule out whether it is caused by the original image file itself, and then confirm whether there is a problem with the ICC file of the output device. Generally speaking, if the overexposed position in the original file is not loaded, If the output device is too large, ICC files will have color spots. The reason why the ICC file is defective may be that the color blocks in the color block file itself are not transitional color blocks but independent color blocks.

Question 18: Which color management instrument generates better output ICC?

Answer 18: The working principles and structures of the color management instruments themselves are similar. The only thing that affects the ICC quality is the color management software. The output device ICC files generated by several color management software currently on the market are in The quality is also different. I can’t say which one is better and which one is worse. They are all moving closer to the international IT8 standard. The output device ICC generated by some color management software will respond better to red, making the red color of the photo more realistic and gorgeous; The output device ICC generated by some color management software will be more realistic in green or other colors. Today, for the silver salt or printing industry, whether it is good or bad is decided by the customer (end product buyer). Customers can spend Spending money to buy your product means that he recognizes your quality. Therefore, the question of "which color management instrument or software is better?" needs to be discussed based on the "customer", because each end customer has a different concept of "good". Similarly, we need to select or modify the ICC file according to its color requirements.

Question 19: If I have two output devices of different brands, can I adjust their colors to be consistent?

Answer 19: It is still possible to be basically consistent. If the liquid (or ink) and consumables (photo paper or printing paper) used by the two devices are the same, then color management can be used to The colors of the two devices should be basically consistent. The basic consistency here means that the results are difficult for non-professionals to distinguish. The reason why it cannot be guaranteed to be completely consistent is because the working principles of different output devices are different. , the developing capabilities of different consumables are also different.

Question 20: How often should the ICC file of the output device be updated?

Answer 20: When the batch number of the output device (or ink) or consumables (photo paper; printing paper) has been changed, the ICC needs to be redone.

Question 21: Is there a universal output device ICC file?

Answer 21: No! Not now, and never again! I once saw someone on the Internet claiming to have mastered the universal ICC file. In fact, these are just gimmicks. Whether it is the output ICC or the ICC of the camera or monitor, they are all unique and directional. Do not mix them.

Question 22: Will ICC files be attacked by viruses?

Answer 22: Yes~! Especially Trojan viruses. I have been depressed about this issue for a long time. Two years ago when I was making an ICC for an output device for a digital output workshop, I found that the generated ICC colors were confusing, but there was no abnormality in the 3D space graphics of the ICC. The colors The management software can also be used normally, but later it was discovered that the computer I was using was attacked by a Trojan virus. After strong anti-virus, I used the same color management hardware and software again to scan the same color block file and the ICC generated was normal.

Question 23: Why is the ICC output effect of my digital output device not as good as that of other devices?

Answer 23: It depends on whether the ICC file you created actually works, because the printing system of many digital output devices is closed loop, and all image files loaded with ICC will be deleted after entering the system. Being replaced by the system's own color grading program is equivalent to saying that all the work done before is in vain. Whether your output device will affect the output color effect depends on whether it is a closed-loop system. If so, you must find a corresponding method to change its closed-loop system to an open-loop system and then use the ICC file.

Question 24: Why do some photos look very good in color when taken indoors, but look much worse when taken outside?

Answer 24: This is a normal phenomenon. This is because the color temperature of the viewing environment has changed. Looking at the same photo in places with different color temperatures will cause different color wavelengths to the human brain. In addition, some The consumable itself contains a fluorescent reflectometer, which will also cause a feeling under fluorescent lights and a feeling under sunlight.

Question 25: What is the workspace of the output device ICC file in PHOTOSHOP and other software?

Answer 25: Just set the working space of PHOTOSHOP to SRGB1966. Do not choose the North American or Japanese color space, because only SRGB1966 (the color space of photoshop5) has the greatest color tolerance and is also most suitable for Chinese people. The degree of color perception.

Question 27: When using PS for color grading, should you first load the ICC file of the output device into the image and then color grade it, or should you grade it first and then load the ICC file of the output device?

Answer 27: There has been an ongoing debate on this issue. I personally think that loading the ICC file first and then color grading is the most ideal state. However, as of now, many output workshops are loading the file in order to improve efficiency. The work of ICC is carried out in the typesetting process. The effect is not bad, because there are many typesetting software that will interfere with ICC files. Experiments have confirmed that loading ICC files into PHOTOSHOP has the best effect and the least loss of details.

Question 28: What is the difference between icc and icm files?

Answer 28: There is no difference between them. The "*.icc" and "*.icm" files are exactly the same except for the different suffixes. "*.icc" is pioneered by Apple and is used on Macintosh computers. Windows on PC uses "*.icm".

Question 29: Is CMYK the abbreviation for Cyan, Yellow and Black? Why not change CMYK to CMYB?

Answer 29: Because the letter B is easily confused with blue, K is used instead. K is the abbreviation of black and also means "Key", which means that black plays an important role in CMYK.

Question 30: If the image file being processed has been manually loaded with an ICC file, what should I do to control the color?

Answer 30: When you use PHOTOSHOP to process pictures, you must first determine what the color space of PHOTOSHOP is. Previously we have mentioned that you need to choose the working space of PHOTOSHOP5. When you select this space, you will find that There are three options in the "Color Management Plan"---the profile does not match (ask when opening); the profile does not match (ask when pasting); the configuration file is missing (ask when opening). After selecting all three options, If it encounters an unprocessed film containing ICC, it will alarm you and you can handle it according to your choice.

Q31: Do digital cameras and scanners need color management?

Answer 31: It is very necessary. I personally think that the color management of digital cameras and scanners accounts for a very large proportion in the entire color management process, because only when the source is controlled can we talk about the quality of the later stage. question. Many output companies will encounter such a problem, that is, they are often returned because the output image color and other aspects do not meet the requirements of the end customer. But is the reason why such a problem occurs must be the output company's responsibility? Not necessarily, because if your source file has color problems during pre-shooting or scanning, then even the most powerful output company may not be able to output the color feeling you want. Take photo studios as an example. Many photographers in photo studios have transitioned from using traditional film cameras. They may not necessarily be able to use digital cameras well. Many photographers dress very professionally (long hair shawls; wearing N pockets). vest), but maybe he doesn’t even know how to do basic camera white and gray balance, let alone take a picture with standard colors. Because of this problem, I need to do color management for digital cameras or scanners.

Question 32: Is it enough to set the white balance of a digital camera to the whiteness of a copy paper?

Answer 32: Of course not, and there are not a few people who use this method. Because there is phosphor on the electrostatic copy paper, you cannot guarantee that the photo will be standard white. When your white balance If it is not done well, all subsequent films will have problems. If you use the method of shooting white paper to solve the white balance problem, it is better to directly use the white balance setting that comes with the digital camera.

The standard for shooting the white and gray balance of a camera is to use a KODAK standard camera whiteboard. This board has a set of 3 pictures, the largest A4 format, white in the front and gray in the back. The white and gray balance transition when shooting with a standard whiteboard will be very comfortable, natural and colorful. The accuracy is also guaranteed.

Question 33: Does the digital camera complete the color management work after setting the standard white balance?

Answer 33: No, this is just the beginning. Later we will use a calibrated camera to shoot professional digital camera color cards. There are many types of color cards on the market, such as: Gmb ColorChecker SG ; Gmb ColorChecker DC; Gmb ColorChecker24 and so on. Only after you actually get the camera's standard color card image can you generate the camera's ICC file in the corresponding software.

Question 34: What should I pay attention to when taking pictures of camera color cards?

Answer 34: There are many issues that need to be paid attention to. For example, the color temperature of the flash in the shooting environment should be controlled at around 5500K. Generally, a studio only has two big lights, and other small lights such as backlight, backlight, etc. , floor lamps, etc. can be ignored. You only need to be able to measure the color temperature value of all the lights flashing together. At the same time, it is best to light the two lights at 45° to the left and right of the color card to avoid reflecting light from the flash on the color card. The best file format for shooting color cards is the original RAW format, because this format has the smallest loss of color in the picture.

Question 35: Can the ICC of cameras of the same brand and model be used universally?

Answer 35: It is best not to do this, because I have not said before that ICC is unique and directional. But I know that many photo studios often use the ICC file of one camera to apply to multiple other cameras of the same brand and model at the same time in order to improve efficiency. The result is not bad, and the color is much better than the color output of files without camera ICC.

Question 36: How to make the ICC of the scanner?

Answer 36: The production method is similar to that of a camera, except that instead of a color card, KODAK standard IT8 positive film or reflection draft is used.

Question 37: Does it take too long for the ICC of a digital camera to be updated?

Answer 37: Unless the hardware of the camera itself is damaged, and when the flash in the studio is replaced, the ICC file needs to be regenerated for the camera.

Question 38: If there is no Kodak standard whiteboard, can I use the tape on the Kodak film box to correct the white-grey balance of the camera?

Answer 38: Many people know that the gray on the Kodak film box is standard gray, but the film box is very small and it is difficult to focus with the camera. When doing white-grey balance, the focus is not good, or the picture is not captured. Complete gray is troublesome.

Question 39: Do high-end digital cameras no longer need ICC for cameras?

Answer 39: It needs to be done. The ICC produced by high-end digital cameras will be more stable and the color reproduction will be more realistic.

Question 40: I want the actual film I made to have the same color as the display effect and output effect. What should I do?

Answer 40: If you already have the camera ICC for shooting the image and the output machine ICC for printing the image, it is easy. You only need to use the PS software to load the captured image into the camera's ICC. file, then load the ICC file of the output device, and then place the output film and object in a standard viewing box (of course, the premise is that the object can be placed in the viewing box). The effect compared with the monitor is very good. What you can see That’s what you get!