Please, visit the Color Mixing Tools page for downloading information. Introduction: This program converts the paint mixture into chromatic coordinates, shows the resulting color on the monitor and also places it in a 3D Munsell Space. Moreover, this system allows experimenting with the effects of various lighting conditions on the paint. In other words, if a particular color mixture is created and painted on a test strip, then placed close to the monitor with the defined lighting condition, the colors on the (calibrated) monitor and those on the paper strip will match and give the same color experience. This system also generates color trajectories between paint mixtures. In addition, various other interesting aspects such as the positioning and orientation of the color wheel, and the color space of both the ideal RGB monitor and the brand of the chosen colors can be visualized. Program description:This program is written as a MATLAB script and for its execution it is necessary to have installed "MATLAB Component Runtime library (MCR)". This is the main interface window of the program version 3.4: In Area 1 we define the paint recipe to be analyzed. Area 2 shows the color resulting from the recipe, while Area 3 shows the spectra. The reflectance spectrum of the mixed color can be saved with the "Save rs" button (4) in a database readable by rs2color. The position of the mixed color and other relationships can also be visualized in Munsell space 3D in Area 5. Up to 4 spectra may be defined in Area 6 and visualized in Area 3 in order to have additional information on the interaction of the reflectance spectra.
The "About" button (10) provides system information with links to websites of interest and MATLAB licensing information (some parts of the document also apply to systems used through the MCR libraries, like the Color Mixing Tools).
In the version number of
the "Color Mixing Tools", the number after the first dot refers to
the number of color brands coded in color2drop
and drop2color, while the number after the second dot indicates the number of
databases defined in rs2color.
By clicking "Exit" (11) or closing the window, several settings get saved such as lighting, selected color brand, etc. In case of unrecoverable errors due to operating system malfunction (with Windows you never know), first the application needs to be closed and then the "drop2color.ini" file canceled from the directory where the program is located: the original configuration will be restored the next time the program starts.
Clicking the "web" (12) button opens the drop2color web page.
Area 1:
Once the color brand is chosen (1), up to 6 color bases may be defined (2). Each color base needs to be selected from the available colors found in the drop-down menu (3) together with the quantity of drops/parts. The quantity can be entered in box (4) or defined by using the cursor (5). A click on the left/right arrow (6) reduces/increases the color drops. The cursor (7) can be moved using the mouse. Moreover, if the cursor is to the far right, a click of the mouse multiplies the increase by ten and moves the cursor to the left in order to further increase the paint quantity.
Area 2:
Since color perception also depends on the lighting of a painting, the illumination spectrum needs to be defined from the list (1). There are 19 preset illumination spectra available:
In color swatch (2), the color provided by the recipe appears with the lighting defined by the first spectrum (1). In zone (3), the RGB and Lab coordinates of this color are shown. It is also possible to define a second illumination spectrum (4). The corresponding color is shown in the lower box (5). If the color cannot be visualized on an ideal monitor (i.e. it is outside of the RGB color space) the "no Gamut" (6) message will appear. The RGB and Lab coordinates of this color will be written in zone (7). The color inconstancy index (C.I.I.) between the two lightings is shown in (8). The C.I.I. is the DE*94 error between the Lab values of zone (3) and zone (7). "Light Strength" (9) refers to lighting intensity. 100% means that the illumination spectrum has an ideal intensity, while it can be lowered to take into account potential dim light. The percentage values are modified to the non linear response of the human eye: for example, a perfect white color with Munsell value 10, with "Light Strength" 50% will be perceived as value 5. If there are no particular reasons to reduce light strength, it is recommended to use value 100%.
Area 3: The spectra are shown as values from 0 to 1 in increments of 0.25 (1). The frequency coordinates (2) go from 380nm to 730nm in increments of 10nm. The color spectra (3) were drawn point by point to show the perceived color with a spectrum zero everywhere, except at one specific coordinate point. The color intensity decreases below 420nm and above 670nm because our eyes are less sensitive in these areas of the spectrum. The spectrum of the mixed color is shown by a thick continuous line (4) with the color perceived with lighting "C". The thinner continuous spectra are the ones with 4 spectra definable in Area 6. The standard observer spectra are colored and dotted (x=red, y=green, z=blue), while the lighting spectra are white and drawn with a dashed line.
Area 5: This area shows the Munsell space (1) defined for lighting "C". (2) shows the Munsell coordinate for the recipe with thick continuous line in Area 3 (or "???" if the color is too far from the color space visible to the human eye). The Munsell space is shown in three dimensions, but starting from a view from top (the Hue-Chroma plane) where one can see the circles (3) with constant Chroma. The distance between adjacent circles is 2 Chroma. The radial lines refer to constant Hue and the name (4) of each principal sector is shown on the larger outer perimeter. The placement of the hue name is next to number 5 of each hue, following the definition of the main sectors of the Munsell space:
The point in the space defined by the coordinates (2) is shown by a sphere (5) colored with the corresponding true RGB value. The position of the sphere is shown on the Hue-Chroma plane while the Value is shown on the line (6), on the grid scale (7) that covers all 10 values of the Munsell space. For each color brand all the mixable Munsell chips are precalculated (from a total of about 2700 of the Munsell Renotation Data). These chips are shown (8) with the correct RGB color. This way one can see the space of the mixable colors at a glance. It is possible to choose (9) to see the chips in 10, 20 or 40 sectors, but if none of the boxes is selected, the chips are not shown. If box 10 is selected, the chips will be lined up with each principal hue sector (of number 5: these are the 10 most important sectors that give the color a name). With the selection of box 20, there is also the number 10 (or 0, from the moment that 0 and 10 overlap), while with 40, the ones with 2.5 and 7.5 are also added which complete the available data. The visualization of the three dimensional Munsell space is shown by a virtual camera. The camera is pointed to the center of the neutral axis (V=5) while the same camera is placed at a certain distance to show the whole space. The camera can orbit horizontally (13-14) and vertically (11) around the Munsell space. The camera can also zoom in (12) by a radial motion. Each of these settings can be activated by keying in a number that represents the angle (13) or using the cursor (14). Moreover, it is possible to face the main planes, like the red-blue/green with the"R-BG" button (15), the yellow-blue/viola with "Y-PB" (16) etc. The "HuCh" (20) button shows the hue/chroma plane from top. Sometimes it is useful to swing around the space to better perceive the position of the colors or the trajectories. This movement can be done by checking box (21). By clicking "Persp" (22), the space is seen in perspective or with orthographic projection (this is the default because this way, from above, the chips are aligned). Choosing a set of paint in Area 1, the space of mixable colors with these bases is calculated (only if box 10 or 20 is selected). The non mixable color chips become transparent. This can answer questions such as whether to use black paint or not, or, if I can mix all the colors from the primary color bases etc., as it is described in the Application Examples section. You may choose to expand the Munsell space from the mixable colors of a selected brand to the entire color space of the human eye with the "EyeG" (Eye Gamut) button (24). In order to see better the relationship between the mixed colors and the color space, you can visualize only one plane crossing the point where the camera is pointing by using the "Slice" button (25) that cuts a slice of the space. This way it is possible to see the classic plane with the Munsell chip that will be completely filled when observing the principal sectors or the planes where the chips are shown. The color of each chip is calculated directly from the Munsell Renotation Data coordinates. If the camera is above or below the plane HC (angle with a vertical range of -90 or + 90), the cursor (26) gets activated to move the target of the camera. The neutral axis value of where the camera is pointing is indicated in (27). Changing the value from 1 to 9, you can see the set of mixable colors in sequence with varying values. It can be noticed that colors with low or very high lightness exist only with reduced chroma. In order to see better the mixable colors there is the "Pnt S" (28) button, Paint Surface, that enables you to see the contour of the mixable colors as a surface. The "rgb S", RGB Surface button (29), on the other hand shows the set of visible colors on an ideal monitor with the white point at 6500K. These surfaces are shown in opaque/semitransparent colors, by selecting/deselecting box "sld" (30), solid, individually or just as gray surface by selecting "gry" (31), gray, for better view in certain cases. Selecting the box "inters" (32), intersection, with "rgb S" (29) deselected, black points are added when the chips do not belong to the color gamut of the monitor. In other words, they are the chips that are outside the color solid defined by all the RGB colors. The box "union" (33), however, adds gray chips to the ones of the color space of the chosen brand to complete also the RGB color space. This way one knows which colors are visible on the monitor, but cannot be mixed, or which colors can be mixed, but not correctly seen on the monitor. If in Area 6 at least two colors are selected, the buttons of the trajectories are activated "T…" (34) in order to be able to draw them. Each trajectory is white with a starting/ending sphere of the starting/ending color corresponding to the group it belongs to. This is extremely useful in seeing how a color changes perceptually when it is mixed with other colors. The trajectories are red in areas which do not belong to the color gamut of the human eye. The button "del all" (37), deletes all the trajectories (that are canceled anyhow every time when the chips are redrawn).
Even if the Munsell space
is defined for lighting "C", there are many curiosities connected to
how the perception changes with varying lightness. Only if the brand Polycolor
is selected can we see the "illum1" (38) button activated that forces
the first chosen lighting. For each color coordinate the XYZ tristimulus
response is calculated using the first illumination spectrum and this gets
transferred into Munsell space using illumination "C", keeping the
XYZ values fixed. If the coordinate cannot be located, it is indicated somehow:
for instance, the trajectories become red in the indefinite zone, or their
terminal sphere gets filled up with red points, etc. A possible color wheel for
each brand has been defined and can be seen by selecting the "Cweel"
(39), Color Wheel, button. The wheel is placed on the plane that better
approximates the single colors of the wheel. This way one can see well that the
neutral axis never leaves the wheel perpendicularly, as it is often shown, but
that the plane of the wheel is tilted: the yellows, in fact, have a high value
(lightness), while the values of reds and blues are much lower. From here
derives a well known fact that when mixing colors, not only the hue changes,
but the value as well. Otherwise, sometimes a color can be brightened also with
yellow/orange/etc. without necessarily using white paint, etc. Button "ShowP"
(40), Show Position, indicates where all colors of a certain brand can be
found. This is useful, for example, to identify the complementary color of a
given paint base or its saturation level. Finally, the
"detach" (41) button allows you to move the Munsell space into an
external window. The advantage is that you can resize this window, save it in
jpeg or tiff formats, have a complete control of the camera and the positioning
of the light to see the surface well: By moving the mouse pointer
over symbols, the function of each button appears. Upon opening the window, the
default selection lets you turn the camera around the Munsell space. This is
much more efficient than using preset commands of the main page, but the exact
position cannot be determined or repeated easily. Moreover, if the mouse moves
while releasing the left button, the space starts to rotate continuously. The
positioning buttons on the main page readjust the camera any time.
Nevertheless, it is a good idea to stop the motion before canceling or adding
data to the image because unpredictable errors may occur. Area 6: In this area you may choose
to draw additional spectra, such as the distribution of the x, y, z tristimulus
functions of the Standard Observers (1), lighting spectra (2) of the selected
illuminations and the reflectance spectra of 4 possible paint mixes. For each
paint base (4) there are four possible options (5), one for each group. In the
example the first color belongs to the first group, while the second color to
the second group. If there are several selections in the vertical boxes, the
recipe obtained from the selected colors will be used taking into account the
paint quantity defined for each base. For each group the color is computed (6)
and the spectrum is also shown in Area 3. Notes: Please read the notes of
the color2drop web page and for further notes and
information, please check the Frequently Asked Question section of the Color Mixing Tools. Application examples:Example 1: Color placement analysis of a mixed paintI choose to analyze the paint mixed by two Polycolor bases: "116- Primary Yellow": 11 parts + "256-Primary Red-Magenta": 1 part. Area 5, point (2) indicates that with light spectrum "C" the Munsell coordinates are 4.4YR 6.1/9.1. Using the "detach" button (41) in Area 5, this window shows up: I can see all the
coordinates (Hue, Value and Chroma). Now, I want to see the
position of this color with respect to other mixable colors of the same brand.
Using the button "Pnt S" (28) of Area 5, I draw the shell around the mixable colors
(i.e. the color gamut) of the Polycolor primaries: With "vertical
orbit" (11) in Area 5, I set the vertical position of the camera at
35 degrees. I notice that the color I have mixed is on the outer shell regarding both saturation and value, that is, I cannot have a brighter color than this one or a darker one without loosing chroma. Now I check my color to see if it can be shown correctly on an ideal monitor by activating the RGB surface with the "rgb S" (29) button in Area 5, both in side and top views: I can see that my color is far from the visualization limits of an ideal monitor. In order to see how these color gamuts are positioned compared to my eyes, I activate the "EyeG" (24), Eye Gamut, button in Area 5. Since the control of the
camera is in the detached window, I have to move the camera farther away or
zoom to see the borders of the eye gamut. With the sixth control button (from
the left) of the camera I activate the Zoom function and upon moving the mouse
I get: Now I can see the strange form of the color gamut of an ideal RGB monitor in the Munsell space. In order to see the color trajectory resulting from mixing "116-Primary Yellow" and "256-Primary Red -Magenta" paints, I check the yellow paint as group 1 and the magenta as group 2, as shown in the picture of Area 6. Now I deselect the Paint and RGB surfaces and press the already activated "T1-2" button (among the buttons (34)) in Area 5. I can see in white the
trajectory I get by mixing Yellow and Magenta in different ratios. It is
curved, as almost all color trajectories in the Munsell space. In order to see
how lightness (Value) varies, I notice that the trajectory is almost aligned
with the principle direction P-GY. Therefore, I press the
"P-GY" button (19) in Area 5. I notice that the value variation has also a non linear behavior. In order to see the trajectory better, I select "Slice" (point (25) in Area 5) to remove all the chips except those along the direction P-GY forming a plane:
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