Getting started with image retouching
We are a big printing company in Shenzhen China . We offer all book publications, hardcover book printing, papercover book printing, hardcover notebook, sprial book printing, saddle stiching book printing, booklet printing,packaging box, calendars, all kinds of PVC, product brochures, notes, Children's book, stickers, all kinds of special paper color printing products, game cardand so on.
For more information please visit
http://www.joyful-printing.com. ENG only
http://www.joyful-printing.net
http://www.joyful-printing.org
email: info@joyful-printing.net
A good printed picture gives a feeling of being comfortable and natural, just as the scene is witnessed and true. Good printing copy relies on good originals, but most of the light or photo originals used in daily printing are often biased by the lens when the film is shot due to environmental or light limitations. These color-changing pictures are very different from our daily visual experience, such as purple skin color, green sky and so on. If you print these color cast images directly without any processing, the effect is certainly not good. It can be seen that, like the original, it is often not the most ideal treatment. A good designer will correct the color cast image so that the final print results can meet the visual habits of the human eye.
Making the image look natural is the basic principle of image retouching. However, this is easier said than done. If you don't understand the printing principle, this requirement is often difficult to achieve. It is often seen that some inexperienced designers work very carefully in Photoshop before the screen, and spend a lot of time thinking that they will get the ideal picture, but the result of the printing is disappointing, it is a pity.
The reason for this is that the designer relies on the screen effect to determine the color of the print. Almost all screens have their own color cast, just a matter of how much. Looking at the same photo with different screens is often quite different. Moreover, the screen is a kind of light source. After a long time, the human eye will produce a natural adjustment effect, adapting to the color cast of the screen, and the color judgment will lose the objectivity, resulting in inconsistent color correction effect. Therefore, the screen is not an ideal tool for judging printed colors.
Mastering the professional color-repairing skills, the first thing is to understand the printing principle, recognize the color of the dot combination, and know the dot data of the reading picture. In this way, it will not be confused by the screen, even if you change the work of another screen, it also gives the same and ideal color correction effect.
Before refining the picture, the first thing to do is to make the correct color judgment. The basis of the judgment is the gray balance of printing. The part that appears to be neutral gray on the screen, if printed is not gray, it means that this is a partial color picture. How to predict the result before the picture is printed, predicting what color will be biased, is the knowledge that the designer needs to master. This kind of knowledge, there is no mystery, as long as you understand the principle, plus practice, you can be familiar with it.
In theory, equal amounts of CMY (cyan, magenta, yellow) inks can be mixed to produce a neutral gray. (That is to say that 50C+50M+50Y can produce 50% gray). However, real-world inks are limited by industrial production conditions. CMY's color rendering ability is not the same. Among them, magenta has the strongest color rendering power, and cyan has the weakest color rendering power. Therefore, the same amount of CMY ink will not be produced. Neutral gray (will be reddish gray), to get neutral gray, you must increase the proportion of c (in) ink, which is the basic principle of gray balance (GreyBalance).
For example, to produce 50% neutral ash, the amount of cyan is 13% more than that of magenta, and the amount of magenta and yellow ink can be about equal. If 30% neutral ash is produced, it is required to be 9% more than magenta. . Different levels of neutral ash, magenta and cyan will also have different mixing ratios. Be especially careful in the light gray part, because the human eye is most sensitive to light color casts. The ratio of cyan and magenta in different cases can be referred to the attached table. Note that the figures here are only a reference. In fact, different brands of inks can make the proportion of outlets 2% to 5%. It is best to compare with your printing manufacturer. They provide different proportions of green and magenta mixed neutral gray for your reference. It will be more accurate when you judge this.
With the neutral gray dot data, it is equivalent to having a reference color ruler, it is convenient to judge the image color cast. Just find out the part of the image that belongs to the neutral gray, and use the color inspection tool to display the dot proportion in photoshop. If the calculated reading is in line with the standard, you can conclude that the image has no color cast, otherwise it will be based on the excess or The standard is lower than the standard, and the image is corrected.
Pictures that look natural are often the result of careful processing by the designer. Some color masters can even correct color pictures with black and white screens. In the process of learning to repair color, it is very important to understand the correct concept. Mastering the relationship of printing gray balance is the basic work of coloring.
If a worker wants to do something good, he must first sharpen his tools. Because the color pictures we produce are finally presented in printed form, understanding the principles, features and limitations of the color printing process is very important for making high-quality pictures. Without this knowledge, it is like sailing without a compass. Everything depends on guessing, it is possible to reach the destination, and it may never reach.
Nowadays, the popular offset printing technology mainly expresses colors by the shape and arrangement of dots. Common dot shapes are dots, squares, and elliptical points, and the size of the dots is expressed in percentages. In general, the minimum point printed on a four-color offset press is 2% and the maximum is 85%. These numbers represent the proportion of the ink-covered portion within a single dot area. Why is the maximum area of the dot not 100%, which is due to the size of the printed dot and is affected by two other factors. The first factor is the total amount of ink at the printing dot (ie, how much four-color ink can be absorbed per unit area). The second factor is "dotgain". Excessive supply of ink will make the paper too moist, causing problems in production, such as affecting registration due to paper deformation. Generally, the total amount of four-color printing is not more than 350%, so the maximum value of individual printing dots It will not be more than 85%.
The dot gain value is the result of the interaction of ink characteristics, printing pressure, and paper ink accepting ability. Among them, the factors of printing and paper are more decisive. In general, the high-gloss flour paper has a small dotgain (about 15% to 20%), and the newsprint's dotgain can be very large (about 25% to 35%), so the same set of film is used to make the zinc plate, and different papers are printed. The color effects can be very different. Relatively speaking, printing pressure is a variable that the printing factory can master. Some printing companies even set the average dot gain of each printing machine under normal conditions for production quality control. Since the amount of dotgain affects the final color effect of the image, it is a variable that we need to take into account when making image retouching.
Before the image is retouched, there is usually a review step, which is to see if the level of the image after scanning is normal. Most of the pictures can be divided into two parts, the bright part (light part), the middle part and the dark part (dark part). This part of the picture constitutes the light and dark level of the entire picture. The problem of beginners and color correction is to pay too much attention to color and ignore the level. In fact, whether the picture is expressive or not, the level is often the key factor.
To master the level changes, you need to start with the light and dark parts. The light position is the smallest part of the CMYK dot total value in the picture, and the dark bit is the largest part of the CMYK dot total value. These two places are the start and end points of the picture level. For easy understanding, you can think of a picture as a room. The light position is the light source in the room. If the light source is bright, the whole house will be brightened. If the light source is dark, the whole house will be dimmed; if the light source is biased toward blue Color, then every part of the house will also have a blue hue. Therefore, whether the dot value of the light position is correct determines the level and color cast of the entire image. The common photo position value is 5C3M3Y or 4C2M2Y. If the light position deviates from these values, it is almost certain that the level and hue of the entire picture need to be corrected.
By the same token, if the value of the dark dot is misplaced, the performance of the entire image will be greatly reduced. If the dark position is set too deep (the value is too large), the details of the dark part will not be expressed, and it will become black. If the dark position is not enough, the black will turn gray and it will look unnatural and unreal. .
Choosing the right light position and dark position is the basis for fully utilizing the expressive power of the picture. Through the understanding of the meaning behind the light position and the dark position value, no matter what picture you encounter, what kind of screen you choose, you can also enjoy it. High quality color pictures.