Digital photography and color management

Discussion on related problems of color management (continued)

Q 1: What kind of monitor needs the calibration of professional instruments?

Answer 1: advertisement; Design; Printing; Enlarge printing; Animation and other fields require true colors; Stable display requires color adjustment of professional instruments. Any monitor, regardless of price; Brand, even the same model; The indicators of monitors produced in the same batch are also different. Low-end monitors are: excellent; Samsung and so on. , with high-end display such as: EIZO；; Compared with apples, it has fine display and good reduction ability, but only stability remains. High-priced displays are relatively more stable. The measured data show that if the working environment of EIZO display has not changed greatly after one calibration, it is not necessary to correct the color of the display frequently. However, low-priced displays such as Youpai still need to be calibrated frequently even if the working environment has not changed much. This is precisely because the stability of low-end displays is not very good. We know that it will affect the display changes. The display is changing at any time, such as the change of ambient light source, but the high-end display will largely eliminate interference factors and slow down the speed of display change.

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

Answer 2: when there is no big change in the light source in the working environment; When there is no big change in the display position; When the computer graphics card connected to the monitor has not changed, we need to adjust the color of the monitor once a week or so. The light source in the working environment can only be seen by visual inspection unless great changes have taken place, and small changes can only be observed by professional instruments such as I 1(EYE-ONE). Theoretically, as long as the color temperature of the light source does not change by plus or minus 300K in the whole working environment, we should be acceptable. However, it should be noted that outdoor stray light interference should be avoided when measuring the color temperature of light source in working environment, because the outdoor color temperature is at 1.

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

Answer 3: That's not true! In order to achieve the same effect as the actual output, it is not enough to simply correct the display, or the work is only partially completed. What you see is what you get is actually the central concept of color management, namely: physical object-display image-output finished product (silver salt; Printing) is relatively consistent in color, which requires us to compare the source equipment (digital camera; Scanners, etc. ); Display; Output device (printer; Printing machine; Printer) for color adjustment.

Q 4: the color of the corrected display feels boring and not as bright as before. Is there anything wrong with the adjustment of the monitor?

Answer 4: Color saturation of the corrected display; It is normal that the brightness is gorgeous before adjustment, because the purpose of adjusting the display is to adjust the color space of the display to an acceptable range for any output device (international IT8 standard), so that the color of the finished product will be closer when it is actually output. We know that color monitors can display 6.5438+0.67 million colors, but the colors displayed by our printing machines or enlargers are far less abundant than those displayed by monitors.

Q 5: 5: Is CRT monitor necessarily better than LCD monitor?

Answer 5: Not necessarily. CRT (cathode ray tube) is a cathode ray tube. This is a widely used display technology.

LCD, the abbreviation of Liquid Crystal Display, is a digital display technology, which can filter the light source through liquid crystal and color filters to produce images on the flat panel. Compared with the traditional cathode ray tube (CRT), LCD has the advantages of small space, low power consumption, low radiation, no flicker and less visual fatigue. Disadvantages: Compared with CRT of the same size, it is more expensive. Many people think that the picture quality of liquid crystal display is not perfect compared with CRT display, which is mainly reflected in bright colors and saturation. However, at present, the indexes of many models of EIZO have reached or exceeded the CRT monitors of the same price, such as the CG series of EIZO. Another point is that CRT display is more easily disturbed by external magnetic field than LCD display, thus affecting the color effect of imaging. Many CRT displays will be magnetized at four corners after a period of use.

Q 6: can the apple monitor be adjusted to the same color standard as the PC monitor?

Answer 6: Yes, we know that the display gamma standard of PC is 2.2, while the display gamma standard of Apple monitor is 1.8. Many people have asked me which is the real gamma standard. Today, I can tell you that the gamma standard is actually 2.2, because the experiment proves that the gamma (contrast coefficient) that our human eyes can recognize is 2.2, which means that we can only see it when the gamma of the display is adjusted to 2.2.

Q 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 multiple monitors can be adjusted to a unified state, but they have not clearly stated whether different brands and models of monitors can be used. I once did an experiment in Hubei, and at the same time adjusted 20 monitors with a high-end monitor calibration instrument, and the results were different. Because even monitors of the same brand and model produced at the same time may not have the same color perception, because there are many factors in the image, and we can only achieve the closest. The high-end monitors are more similar, but the low-end monitors are much worse. I also put four brands at the same time; A total of 15 monitors of six models were adjusted to basically the same state by the display adjuster, but it was of no practical value. This is because all 15 displays have different degrees of attenuation. The reason why I can adjust to a relatively uniform state is because I take the worst indicator in 15 monitor as the standard, and other 14 monitors are close to it. In fact, as long as each monitor is measured according to the adjusted standard, it will be closer to the international color standard, in other words, the color performance is closer.

Q 8: Does the monitor need a range hood?

Answer 8: Absolutely! Some friends think it is not very convenient to use the display screen after adding a hood, and it is wrong to simply use the hood. We know that the display is a luminous body, so the external light source has great interference to our identification of the correct color of the display. For example, when the color temperature of the external light source reaches 6500K, our display is only 5500 K. At this time, when the external light source shines on the display, we will find that the color of the display has changed. A good hood can greatly reduce the color interference of external stray light on the display. The price of range hoods sold on the market now is relatively expensive, mostly several hundred yuan. Some friends may ask why it is so expensive. In fact, at this time, due to the raw materials for making the hood, the materials for making the hood are mostly pure black, which has a strong anti-reflection function.

Q 9: Can ICC documents of the same brand and model be used interchangeably?

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

Q 10: How long is the appropriate time for the display to be calibrated?

Answer 10: Generally speaking, the monitor can be calibrated after half an hour, because the indicators of the monitor tend to be stable and suitable for calibration, while the EIZO monitor can be calibrated after 3 minutes.

Q 1 1: Why do I calibrate the same CRT monitor with the same instrument, but the effect after calibration is not as good as others?

Answer 1 1: This may be because you adjusted the display menu too quickly when correcting the display. We know any operation of CRT display, such as adjusting brightness; Contrast, etc. , determined by the temperature of the CRT. Sometimes we adjust the speed too fast and enter the next state before the CRT reacts. Of course, we can't get the best display correction effect. We should develop a good state, that is, when you calibrate the CRT monitor, don't adjust the speed of the monitor too fast, and wait at least 5 seconds after each adjustment before fine-tuning until the next operation.

Q 12: I want to set the monitor of my notebook to the standard color state. Can I do that?

Answer 12: It depends on the configuration of your notebook. There must be a discrete graphics card, such as ATI MOBILITY RADEON series. The level of graphics cards is naturally higher. Of course, the graphics card of the notebook is basically not too low.

Q 13: how to display ICC files?

Answer 13: the display device feature file is what we usually call the display icc file. Icc is actually the abbreviation of "International Color Alliance", and the icc file of the display is a file supporting RGB. It can be called by the system as a configuration file of the monitor. The use of ICC file of display is very simple. Right-click on the computer desktop to enter the properties, and select Settings-Advanced-Color Management in the properties to select or view the ICC file of the monitor.

Q 14: Will the bad spots on the display affect the color accuracy?

Answer 14: Generally speaking,no. When any monitor leaves the factory, as long as the number of bad spots is less than three, it is within the normal range, but if there are obvious lines on the monitor, it will affect the color of the monitor.

Q 15: what should the output device pay attention to when making ICC files?

Answer 15: If you want to generate the ICC file of the output device, the preliminary work is very important. If it is a digital printer with silver salt process, we must first determine whether its printing scheme meets the standard (configuration ratio; The temperature of the potion; Supplementary amount of liquid medicine; If it is inkjet printing or printing machine, it is necessary to determine the quality source of ink, the quality of paper consumed and the amount of ink. The biggest difference between silver salt process and printing process is the different workspace. Silver salt is RGB and printing is CMYK. When the above points are confirmed, we only need to turn off all the source color settings when the printout device manages the color blocks. Pay attention to consistency when scanning color block files, and prevent the laser light source of color manager from mixing with other colors when scanning.

Q 16: Is the ICC file generated by more color blocks in the color block file of the output device the most perfect?

Answer 16: Not necessarily. Many people have asked me the same question, and we have done many experiments to prove that as long as the number of color blocks reaches 9 18, it is enough to represent the color gamut space of any output device. Italian POLI machine in silver salt process; ZBE darkroom sound reinforcement equipment in America; Norris 32/33/24 series; Tailai; Zhetha series and other models have made more than 9000 color block files, and its effect has no obvious advantage compared with 9 18 color block. We did it at KD2 100; The experimental results on HP INDIGO5000 and other printers are the same.

Q: 17: The ICC file of the output device we made is not effective when it is applied to the original picture file. What's the problem?

Answer 17: First, we need to rule out whether it is 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 ICC file of the output device is not suitable for the overexposed position in the original file, color spots will appear. The reason why ICC file is defective may be that the color block of the color block file itself is not a transitional color block but an independent color block.

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

Answer 18: The working principle and structure of the color management instrument itself are similar. The only thing that affects ICC quality is color management software. At present, the quality of ICC files generated by several color management software on the market is not the same, and they are all moving closer to the international IT8 standard. Some output devices ICC generated by color management software will respond better to red, which will make the red color of photos more realistic and gorgeous. The output device ICC generated by some color management software will be more realistic if it is restored to green or other colors. Today, for the silver salt or printing industry, whether it is good or not is decided by the customer (the buyer of the final product). If the customer can spend money to buy your product, it means that he recognizes your quality. Therefore, the question of "which color management instrument or software is good" needs to be discussed by customers, because each end customer has a different concept of "good".

Q 19: If I have two different brands of output devices, can I adjust their colors to a unified state?

Answer 19: basically the same is ok. If the liquid medicine (or ink) used by two devices is the same as consumables (photographic paper or printing paper), then the colors of the two devices can be basically consistent with color management. By basically the same, I mean that it is difficult for non-professionals to distinguish the effects. The reason why it can't be completely consistent is that different output devices have different working principles and different consumables have different development capabilities.

Q 20: How often does the ICC file of the output device need to be updated?

Answer 20: When the medicine (or ink) of the equipment is output; Or consumables (photographic paper; Printing paper) You need to do ICC again when changing the batch number.

Q 2 1: Is there an ICC file for the universal output device?

Answer 2 1: No! Not now, not ever! I once saw someone claiming to have mastered the universal ICC file on the Internet. In fact, these are just gimmicks. Whether it is the output ICC or the ICC of the camera or monitor, it is unique and directional, so don't confuse it.

Question 22: Will ICC files be attacked by viruses?

Answer 22: Yes ~! Especially Trojan horse virus, I have been depressed on this issue for a long time. Two years ago, when I made the ICC of an output device for a digital output workshop, I found that the generated ICC was chaotic, but there was nothing abnormal in the 3D space graphics of ICC, and the color management software could be used normally. Later, I found that my computer was attacked by Trojan horse virus. After strong antivirus, I scanned the ICC generated by the same color block file again with the same color management software and hardware.

Question 23: Why doesn't my digital output device use ICC output like other devices?

Answer 23: It depends on whether the ICC file you made really works, because the printing system of many digital output devices is closed-loop, and all the image files loaded with ICC will be replaced by the color matching program of the system itself after entering the system, which means that the previous work 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 need to find a way to change its closed-loop system into an open-loop system, and then use ICC files.

Question 24: Why do some photos look good in the house, but they look much worse outside?

Answer 24: This is a normal phenomenon. This is because the color temperature of the observation environment has changed. When the color temperature is different, the color wavelength of the same photo is different. In addition, some consumables themselves contain fluorescent reflectors, which will also cause the next feeling of fluorescent lamps. The feeling in the sun.

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

Answer 25: Just set the workspace of Photoshop to SRGB 1966. Don't choose the color space of North China or Japan, because only SRGB1966 (the color space of Photoshop 5) has the greatest color tolerance and is most suitable for people's perception of color.

Question 27: When using PS for color matching, should the ICC file of the output device be loaded into the image before color matching or after color matching?

Answer 27: The debate on this issue has never stopped. Personally, I think it is the most ideal state to load ICC file first and then color it. However, in order to improve efficiency, many output workshops put ICC loading in the typesetting process. The effect is also good, because there are many typesetting software that will interfere with ICC files. After experiments, it is confirmed that the ICC file is loaded into PHOTOSHOP with the best effect and the least loss of details.

Question 28: Is there any difference between ICC and icm files?

Answer 28: There is no difference between the two. File "*. Icc "and" *. Icm "is the same except the suffix. "*.icc" was invented by Apple and used for MAC computers. Windows of PC uses "*". icm”。

Question 29: Is CMYK the abbreviation of cyan, yellow and black? Why not change CMYK to CMYB?

Answer 29: Because the letter B is easily confused with blue, it is replaced by K, which is the abbreviation of black and also means "key", indicating that black plays an important role in CMYK.

Question 30: If I have manually loaded the ICC file before processing the picture file, how can I control the color?

Answer 30: When you use PHOTOSHOP to process pictures, you must first determine what the color space of PHOTOSHOP is. As we have mentioned, you should choose the workspace of PHOTOSHOP5. When you choose this space, you will find that the "color management scheme" has three options-the configuration file does not match (opening is asking questions); Configuration files do not match (ask questions when pasting); Missing configuration file (ask questions when opening). After all three options are selected, if there is ICC in the raw film, an alarm will be given and the processing can be carried out according to the selection.

Q 3 1: Do digital cameras and scanners need color management?

Answer 3 1: Very necessary. Personally, I think the color management of digital cameras and scanners accounts for a very large proportion in the whole color management process, because only by taking good care of the source can we talk about the later quality problems. Many export companies will encounter such a problem, that is, they will often be returned because the color of the output image does not meet the requirements of the end customers. But is it the responsibility of the export company to have such a problem? Not necessarily, because if your source file has color problems in the early stage of shooting or scanning, even the most powerful output company may not be able to output the color feeling you want. Take the photo studio as an example. Many photographers in the photo studio have transformed from using traditional film cameras. They may not be able to use digital cameras well. Many photographers wear professional (long hair shawls; Wearing a vest with n pockets), but maybe he is even at least white with a camera; I can't even balance the gray, let alone make a standard color film. It is precisely because of this problem that I need to do color management for digital cameras or scanners.

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

Answer 32: Of course not. There are not a few people who use this method. Because there is phosphor on the xerographic paper, you can't guarantee that it is standard white. When your white balance is not done well, there will be problems in the films taken later. If white paper is used to solve the problem of white balance, it is better to use the white balance setting that comes with the digital camera directly. The standard of the white-gray balance of the camera is to use Kodak standard camera whiteboard, a set of 3, the largest A4 format. The white-gray balance transition shot with the standard whiteboard will be very comfortable and natural, and the color accuracy will be guaranteed.

Q 33: Has the digital camera finished color management after setting the standard white balance?

Answer 33: No, this is just the beginning. After that, we will shoot professional digital camera color cards with calibrated cameras. There are many kinds of color cards on the market, such as Gmb ColorChecker SG；; Gmb color check DC; Gmb ColorChecker24 and so on. When you really get the standard color card image of the camera, you can generate the ICC file of the camera in the corresponding software.

Question 34: What should I pay attention to when shooting the camera color card?

Answer 34: There are many problems to pay attention to. For example, the color temperature of the flash in the shooting environment should be controlled at about 5500 K. Generally, there are only two headlights in a studio, and other small lights such as backlight, backlight and floor lamp. It can be ignored, so it is only necessary to measure the color temperature values of all the lamps flashing together. At the same time, it is best for the two lamps to avoid illuminating the color card at the left and right angles of 45 degrees to avoid the reflected light flashing on the color card. The file format of shooting color cards is preferably the original format of RAW, because this format has the least color loss.

Question 35: Can ICC of unified brand cameras be universal?

Answer 35: It's best not to, because I have never said that ICC is unique and directional before. But I know that in order to improve efficiency, many photo studios often apply ICC files of one camera to other cameras of the same brand at the same time. The effect is ok, which is much better than the color of the file output without camera ICC.

Question 36: How to make ICC of scanner?

Answer 36: The production method is similar to that of a camera, except that it is not a color card, but a Kodak standard IT8 positive or reflective manuscript.

Question 37: Is it too long to update ICC of digital camera?

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

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

Answer 38: Many people know that the gray on Kodak film box is standard gray, but the film box is very small and it is difficult to focus with a camera. It is very troublesome to focus badly when the white gray scale is balanced, or to take a complete gray scale.

Question 39: Don't high-end digital cameras need ICC?

Answer 39: Yes, the ICC made by high-end digital cameras will be more stable and the color reproduction will be more realistic.

Q 40: What should I do if I want my film to have the same color as the display effect and output effect?

Answer 40: If you already have a camera ICC to take pictures; An output machine ICC is used to print images; It's easy. Just use PS software to load the ICC file of the camera, then load the ICC file of the output device, and then put the output film and objects into a standard view frame (provided that the objects can be put into the view frame, of course). Compared with the monitor, the effect is excellent, what you see is what you get!