Calibrating the monitor
Calibrating the monitor is a necessary preparatory stage for prepressing photos and images, without which all efforts to select the most suitable and effective colors will be in vain. Incorrect color reproduction will result in that the printed photos will be too dark or, conversely, lighted, and people's faces will acquire an unnatural shade.
Calibration of the monitor can be carried out with the help of special calibrators intended for this, however such a device is not available for every photographer. In the first part of this article, we will look at those methods that will allow the monitor to be calibrated without the use of additional equipment.
Preliminary stage of preparation of the monitor for colibrating
When choosing a monitor, discard modern LCD devices intended for passing games, as often their manufacturers often reduce the bit depth of the LUT in order to increase the speed of updating the picture. The optimal solution is to purchase an accurate monitor with an 8-bit LUT, whose role will be especially noticeable as the device ages.
Before you begin to calibrate the monitor, make sure that you really need it. If you are not a computer artist, but a simple user, and your main task is to type texts, calibrating the monitor can only lead to the fact that you will overexert your eyes as a result of high brightness, and the monitor itself is much faster.
Make sure that the monitor is clean and not covered with a layer of dust. In order to wipe the screen, it is better to use special means or, in extreme cases, alcohol.
Try to ensure in your room a constant dim illumination. During the day, you can mute the sun's rays with a blind, at night you should use a daytime white lamp. A conventional incandescent lamp will not work for you, since its spectrum is narrower. For the top light it is recommended to use lamps that give scattered light.
Brightness and contrast adjustment
Adjusting the brightness and contrast is the simplest, but at the same time and the least accurate way to calibrate the monitor. The advantages of the method are that it does not require the presence of a color profile, so it is perfect not only for everyday use on your PC, but also in cases where you need to make adjustments on someone else's computer.
The tests below are designed to help you choose the optimal contrast and brightness settings. A quality monitor should be able to pass both tests. If this does not work out, decide which one will be more important to you. Before testing, make sure that the monitor has already heated up sufficiently, for which it may take 10-15 minutes.
Calibration of halftones is usually the most important task in the pre-print setting of the monitor. In the figure below, the color of the square in the center should be similar to the background color, the left square - to be darker, and the right one - to light. If the center square looks brighter or darker than the main background, your monitor displays images brighter or darker, which will definitely affect the quality of the print.
To adjust the LCD monitor, you need to set a standard contrast for it (usually 50% or 100%), and then adjust the brightness until the center square merges with the background. For a CRT monitor, the maximum contrast should be set. Be sure to make sure that the monitor is set to gamma 2.2.
Increasing the brightness of the monitor can lead to the fact that the period of its performance will end faster. Therefore, before making changes to the brightness settings, make sure that it is not influenced by excessive room illumination or a light source located behind the monitor, for example a window.
Details in the light and in the shadows
After you make the previous setting, all halftones on your monitor will have the necessary brightness level. In order to confirm the correct settings, take a look at the images below.
Details in the shadows
Details on light
In each image, 8 steps should be distinguishable, while the extreme should be barely discernible. Before making the settings, decide what is more important for you - half-tone illumination or maximum details. Too high brightness will cause the black to change to gray. The above settings allow you to adjust part of the tonal range and almost do not affect the color. More accurate calibration can be done only with the use of special instruments.
The simplest ways to calibrate a monitor
The more colors your monitor displays, the more subtle work with images you can perform. Therefore, adjust your video card to the maximum depth of color and set the contrast to the maximum. After that, adjust the brightness of the display so that the borders between the transitions in the figure below are clearly visible, but the transition between 0 and 5 was barely noticeable.
Look at the picture below, there are several squares. No pixel on the screen should be more black than one of them. The black border around the screen should be exactly the same black as this square. Look at the white square. Its color should be really white, without blue and pink shades.
Step away from the monitor one step: one of the squares in the figure below should be shaded as well as the background around. The figure in its center indicates the gamut of your screen.
Another calibration test is developed using Adobe Gamma technology. The black square in the figure below should barely differ from the background surrounding it. The background of the gray square is just as bright as the surrounding hatching.
Calibrating and profiling the monitor
The complexity of prepressing images is that the same color can be reproduced in completely different ways on monitors, differing from each other by tuning parameters, the manufacturer and even the duration of operation.
Calibration of the monitor is designed to eliminate the difference between the digital value of the color and its visible display, and involves changing the physical parameters of the monitor (brightness, contrast, color), and creating a so-called Look-Up Table .
LUT takes the original color value from the image file, and then determines that the monitor shows it darker or brighter than it should be, and makes appropriate adjustments to the display. Thus, the Look-Up Table task is to convert the digital value of color to a new one, which will correct all the existing shortcomings of the monitor.
Due to the fact that different devices usually are not able to reproduce the same range of chroma and shadows, profiling, which is carried out with the help of special programs, is very important for setting up the monitor. Supporting color management software uses color profiles to achieve a minimal difference between the original and the converted image.
Devices for calibration of monitors
The devices for calibrating the monitor allow for both calibration and profiling. Most calibrators look like a computer mouse and are attached to the display. In the set with the device there is a program showing on the monitor a consecutive set of colors and tones, which are measured and recorded by the device.
The most common calibrators are:
- ColorEyes Display,
- ColorVision Spyder,
- Rite Eye-One Display,
- ColorMunki Photo.
Begin calibration after 10-15 minutes after turning on the monitor to allow it to warm up. This will ensure the stability of the brightness and balance of color. Next, you will need to set the monitor parameters, which will be used for calibration. These parameters include the white point, gamma and brightness. During the setup, you will need to change some monitor settings, including its brightness, contrast and RGB values, if you use a CRT.
As a result, you should get a matrix of color values and their corresponding parameters. The device will create a Look-Up Table that will reproduce neutral and accurate shades of gray, as well as matching the hue and color saturation.
There are several parameters, the values of which need to be determined for calibration of the monitor.
A white point is needed to determine the heat or coldness of the lightest display. Increasing the color temperature makes it possible to get colder tones, and its decrease is warmer.
The standard recommended temperature for a CRT monitor is 6500K (or D65). It's a little colder than normal daylight. Adjustment of LCD monitors is more difficult due to the fact that their backlight always has its own color temperature, which can not help but affect the image. In this regard, it is usually recommended to leave the color temperature of the LCD monitors unchanged, unless you clearly need to change it.
Gamma controls the speed of increasing the brightness of the shadows in the transition from black to white. Has a significant effect on the contrast of the image, and also makes it look lighter or darker.
Currently, the standard for editing and viewing images is gamma 2.2, which is the closest to the monitor's settings, as well as to the perception of variations in brightness by a person.
Brightness determines the amount of light emanating from the monitor. The setting of this parameter depends entirely on the level of illumination of your environment, including daylight or electric light in the room, as well as its additional sources. The most common value of this parameter is 100-150 cd / m2, however, if you work in a room with strong lighting, you will need to change the brightness of the monitor.
How the Look-Up Table works
The LUT is controlled by a video card or the monitor itself, so its use does not depend on whether the software supports color management. LUT loading starts immediately from the beginning of the operating system, and its use is carried out, regardless of what is on the display.
To better understand the work of the LUT, let's take a look at how different the gray color might look, which should be displayed on the monitor in case the values of red, blue and green are equal. The task of the LUT is to maintain the gray tones in the correct gamut.
In some cases, several LUTs participate in creating an image on the monitor, and not just the one that is in the video card. A particularly accurate calibration can be achieved using the adjustment of the built-in monitor LUT, but not all models allow this.
What is the color profile for?
The color profile is necessary for converting images in such a way that they are displayed as correctly as possible, taking into account the characteristics of the monitor. Unlike LUT, which starts working immediately after system startup, in order to use the color profile, appropriate programs that support color management are needed. For this purpose, you can use Adobe PhotoShop or another program for editing images or working with the format of RAW.
Each time the program opens an image containing a color profile, the program compares it with the monitor profile and, if there are differences between the chroma spaces, transforms them.
How to check the calibration quality
Not always the device can perform its task qualitatively, therefore every time after calibrating the monitor it is necessary to check how it was implemented. And even if you find that your monitor can not be configured better than this device for calibration, you can take this disadvantage into account when editing images.
The easiest way to assess the quality of the calibration is to open a large black and white gradient in the color management support program. If the transitions between the tones are not uniform, then, most likely, the monitor has been calibrated poorly.
Compare the two pictures below to see what a substandard calibration looks like.
Setting up printing equipment
The overall calibration of the monitor will avoid color distortion when printing on most printing equipment, but in some cases, in order for the image to be printed to match the picture on the monitor, you must find a special file for your printer to correct ICM.
Usually they are on the official website of the manufacturer. This color profile can be opened in any professional program for working with images - Photoshop, CorelDRAW, Microsoft RAW, etc.
The color profile is set directly in the editor program itself. For example, in PhotoShop for this, go to the "Edit" menu and select the "Color Settings" option. Clicking the "Download" button allows you to install a new profile into the program.