How colors and effects are expressed

In this paper, three different recognition methods for paint color matching are summarized. A precise description of the method is important, especially for the effects of aluminum powders and light interference pigments, which depend heavily on the angle of the measurement selected. The measurement angle defines the combination of the lighting angle and the observation angle at the time of measurement, and the established light source angle accurately matches a
chinese
. The three methods are: visual matching by the window sill or in the light room, measuring with the relevant measuring equipment, and describing the optical properties.
the window sill and tilt the model up and down in the direction of light. The model also usually flips in direction, with an upright back to the light source. For walk-in light rooms, they are evaluated in a similar way to the window sill. There is a table or a work table in the light room where the tester can sit and experiment. In a light room, a model is usually placed in the path of light exposure - the light source is usually hung at the top of the light room - for evaluation.
the use of the instrument, the measuring instrument needs to be placed on the sample plate, which is illuminated during measurement and the reflected light is measured. The physical values of these measurements are then converted into perceived color data. Reflection curves are useful when evaluating the color effect of a coating. In particular, the reflective curves of light interference pigments reveal a great deal of information about pigments and their optical properties.
today, portable measuring instruments are still measured from multiple angles, with the addition of -15 degrees. In the early days, these measurement angles were used to test metal effect coatings. In the late 1980s, the same instruments and angles were used for the measurement of light interferon pigments in emerging coatings, without taking into account the physical and optical properties of these pigments. The color and effect of aluminum pigments and light interference pigments are highly dependent on the measurement angle, i.e. the combination of lighting and observation angle. This measurement angle is applied to visual evaluation as well as instrument evaluation. Ideally, both approaches should get the same result. Because the instrument evaluation is derived from the visual evaluation: the physical reflection value. Instrument measurements are converted into perceptive color data to reflect visual impressions. However, it has been criticized by paint labs because observations by windows or in light rooms cannot be associated with measurements, especially when evaluating effective coatings. The paradox is not the inaccuracies or errors in the measurement method, or the converted color data, but rather the use of different measurement angles in visual and instrument evaluation. The choice of measurement angle plays a decisive role in both evaluation methods. In particular, the optical properties of light interference pigments are determined by the measurement angle chosen.
the third method is to describe the optical properties of the pigment effect. And the language described needs to be able to recognize and depict. For example, different types of aluminum pigments should be represented differently. Light interference pigments are specifically represented according to their optical principles. Compare the apparent optical properties to corred with the other two methods.
visual
is performed at the window sill, and the primary position of the model is for the observer to see the gloss of the model. At this starting position, the gloss angle (the angle at which the light is reflected) is the same as the lighting angle, and the vertical
of the model is right in the middle of them. For example, suppose that the angle of the incoming light is -15 degrees, and accordingly, the angle of the reflected light is -15 degrees. It is used here as a convention angle, with the angle on one side of the incoming light specific to positive values and the angle on the observer side specific to negative values, although according to optical principles, the angle of the actuation light is equal to the degree of the angle of reflected light.
now the observer tilts the model or tilts it forward or back toward the observer. In any case, the angle between the observer and the light source remains the same, always at 30 degrees in the example. On the other hand, when measuring with a portable instrument, the angle between the lighting and the observer changes with each measurement angle selected.
if the observer moves the tilted model closer to itself, the angle of the incoming light increases. At the same time, the angle between the observer and the glossy angle (inverse mirror) is increased. For example, if the angle of incoming light is increased from .15 to 45 degrees, the angle of gloss changes from -15 degrees to -45 degrees. The angle of the observer becomes 15 degrees, which changes 30 degrees from the angle of the incoming light. At this point, the angle of observation and gloss (inverse mirror) is 60 degrees (see Figure 1).If the model will be moved far away from the observer and the back-up model, then the angle of the starting incident light will move toward the main line, for example, from .15 to .5, the corresponding gloss angle is -5 degrees, and the angle of the observer will change
to -25 degrees. At this point, the angle angle between the observation angle and the gloss angle (inverse mirror) is -20 degrees. If the observer tilts the model back further, the incident light angle moves to the other side of the main line, for example to - 1 0 degrees. Then the angle of the gloss moves to the other side of the main line, and the angle of the observer becomes -40 degrees, and the angle between the observer and the gloss (inverse mirror) becomes 50 degrees.
important thing to consider when tilting the model up or down: because of the reversal of light, the color values can be almost identical. For example, the measurement of
by lighting and -20 degrees should theoretically be consistent with observations of lighting at .20 degrees and -10 degrees. You will find that when you pour the model, the measured values recorded are almost the same as between the back-up models. This difference is very subtle for the eye and is considered to be the same color or the same gradient color in actual perception. Basically, the observer will get the same color feel regardless of whether the model is forward or back (see Figure 2).the above phenomena vary widely on different scraping samples because of the orientation of the scraping, which can be clearly seen by measurement. However, the difference in spray samples is small. But it is also related to the quality of the sample spray.
other observations produce the same result: if you turn the model upside down, have it measured back to the window, and then tilt the model forward or back, you can get the same result. Even in a walk-in light room, you can find something similar. and other color light boxes designed according to the customer's specifications. In this article, the model piece is usually illuminated vertically from above or at 45 degrees, followed by the model tilted forward or back. Compare at various angles in turn (see Figure 3).don't forget that visual inspection can only be done in one direction: the sample plate is significantly larger than the measuring point area of the instrument. When the observer observes a model of a conventional size at a conventional viewing distance, the viewing angle is approximately 20 degrees between the top and bottom edges of the model.
visual inspection begins at an angle close to the gloss, and when the model is tilted forward or back, the observer continues to leave from the gloss angle, leaving them away from the window and into the position of the light unchanged. The lighting angle of the portable measuring instrument remains the same, changing the observation angle. For light interference pigments, they have more or less obvious color conversion, and the instrument measures in different ways to obtain more than one measurement.
instruments evaluate
effects and gradients of color, especially light interference pigments, which are highly dependent on the angle at which they are exposed to light sources and the angle at which they are observed. The different angles used for portable devices than those used in visual evaluation do not represent the quality of their tests. The fewer angles you select, the more you limit the amount of measurements you can get, which requires additional measurements. Even adding the gloss (inverted mirror) -15 degree angle defined in the ASTM standard test method requires a lot of measurement work by many users. Even today, what happens in the measuring device and the meaning of the angle name is still inexplicable for many users (Figure 4).the addition of colored pigments tocoatings only shows little or no effect of color conversion, and in practice, when aluminum silver paste is added to the coating, the luster changes with the measurement angle. The brightness is greatest at the glossy angle, and the brightness away from the glossy angle decreases. This phenomenon can be described using measurements from portable devices. Measure the sensor gradually away from the glossy angle by fixing an angle of illumination. This method can record the phenomenon of brightness changes, which is also the result of visual description at different angles. For example, for coatings mixed with carbon black pigments: when using a more delicate carbon black pigment, the paint is blue. In the case of thicker carbon black particles, the paint will be brown. After mixing the same amount of aluminum silver paste into the carbon-black coating. Looking at the paint from an angle close to the gloss, the blue carbon-black aluminum paint looks darker than the brown carbon-black aluminum paint. The rate of change in brightness depends on the distance from the glossy angle: paint mixed with blue carbon black becomes brighter than paint mixed with brown carbon black. This can also occur in coatings mixed with light interference pigments. Changes in brightness can be described visually or by instrument measurements.
Compared to visual evaluation, one advantage of instrument evaluation is the ability to observe the color performance of color transparent interfering pigments: if the corresponding coating is coated on a white base plate, changes from reflection to transmission color can be identified. These pigments have a typical reflective color on their surface, and since there is no phase shift, the light that penetrates the pigment produces complementary transmission colors on the back. The measuring instrument illuminates at a fixed angle, changing several different angles (reverse mirroring) measurements starting from the gloss angle to ensure an accurate description of its optical properties: depending on the pigment type, there is a media area between 20 and 30 degrees (inverting mirroring), which is usually also the area where the change occurs.
portable instrument can reveal some of the color properties of the coating based on the angle chosen. Visual matching can reveal the color properties of different parts of the coating. This results in different results. Therefore, the combination of the two assessment methods is very important to arrive at the optimal assessment results.
the characteristics of optical
the third aspect of color evaluation involves optical properties. These assessments were initially independent of the above visual and instrument evaluation methods. The description of features raises the question of whether and how they can adapt to the first two approaches.
aluminum pigment changes its brightness when irradiated at different angles or at the same counter-mirror angle. Similarly, when the lighting angle is fixed and observed at different inverse mirror angles, the brightness changes. Looking at the corresponding reflection curve, you can see that only the brightness level changes, there is no phase displacement.
interfering pigments show eye-catching color According to the principle of light interference, light interference pigments react to changes in the angle of lighting. At the same angle of view, when these pigments or the corresponding coatings are evenly irradiated, the reflective curve migrates in a shorter wave direction. For example, red interferon pigments migrate to the yellow phase, while yellow interferon pigments migrate to the green phase and green interfering pigments migrate to the blue phase. This performance is clearly represented by the reflective curve and the color value of a*b*color obtained by the measurement that changes the illumination angle.
this behavior is typical of each light interference pigment and can also be used to identify light interference pigments. The characteristics of a light interference pigment can be described by measuring its interference line of 15 degrees/15 degrees, -45 degrees/15 degrees, - 6 5 degrees / 1 5 degrees and the reverse mirror line 4 5 degrees / 1 5 degrees, - 4 5 degrees / 2 5 degrees, -45 degrees / 45 degrees (illumination angle/observation angle). Connecting with 45 degrees/25 degrees, -45 degrees/15 degrees, -65 degrees/15 degrees, the arms of the curve always point in a counterclockwise direction of 45 degrees/15 degrees, -65 degrees/15 degrees (see Figures 5 and 6). these angles cannot really be realized in portable instruments, and due to the principle of light reversal, the instrument's measurement angle of 45 degrees/-15 degrees can be used instead of 65 degrees/15 degrees observation angle. The illumination angle is 45 degrees and is observed at -60 degrees (equivalent to inverse mirroring -15 degrees). If we reverse the light path, the illumination angle is 60 degrees, while the observation angle is 45 degrees (equivalent to 15 degrees in reverse mirroring); Using this "trick" (see Figures 7 and 8), the optical properties of an interfering pigment can be partially captured.
summary All three descriptions have their advantages: visual evaluation moves the model forward or back more like humans (Figure 9). In most cases, the two model pieces are compared to detect the color difference. Portable instruments can be measured as long as there is a chromation at a given measurement angle. Optical performance requires different measurement angles to define and distinguish interfering pigments. If you want to visually evaluate them, it is recommended that you move the models from top to bottom in parallel so that you can change the angle of the lighting at the same time. If you grasp the model and flip it back and forth, the model should be treated more evenly. If you lower the model, its lighting and observation angles will become steeper and steeper. If you want to get close to the portable measuring instrument, you need to include a measurement angle of 45 degrees/-15 degrees. Data from the multicolored light interference pigments at 45 degrees/15 degrees and 45 degrees/-15 degrees will turn, while the data related to the measuring angle of the aluminum powder pigment will be in a straight line, while the data related to the measuring angle of the aluminum powder pigment will be in a straight line, while the steering will occur at 45 degrees/25 degrees and 45 degrees/15 degrees.
Werner Rudolf Cramer, Minster, Germany