RAL 4005 colour belongs to RAL Classic Color System, a colour matching system mainly used for varnish and powder coating but nowadays there are reference panels for plastics as well.
In the 1915, Albert H. Munsell designed a color system based on a three-dimensional color solid [26]. These three dimensions, namely hue, chroma, and value, are perceptually uniform and independent. In his first attempts, he tried to represent the color solid system with regular solid shapes (e.g., sphere, cube, pyramid, cylinder), until he empirically came to an irregular cylinder capable of reaching the best estimation of human visual response. Hue represents the color appearance parameter. It is used to distinguish between reddish, greenish, blueish, and other degrees of color. In the Munsell color system, hues are measured with angle degrees around the cylinder central axis, divided into five principal hues (i.e., red (R), yellow (Y), green (G), blue (B), and purple (P)) and five intermediate hues (i.e., yellow-red (YR), green-yellow (GY), blue-green (BG), purple-blue (PB), and red-purple (RP)). Neutral color hues (N) can be found in the very central axis of the cylinder. Indeed, lightness (value) of a color is related to height of the cylinder. Its range spans from pure black (0) to pure white (10). The last dimension to be defined is the one related to chroma parameter, measured radially from the central axis. Its scale starts from 0 (for neutral color hues) and has none arbitrary end. This is the reason why the cylinder can be considered an irregular solid. However, limits for chroma parameter have been set by the so called MacAdam limits [22].
Nowadays, the Munsell color system is recognized in several international standards, like the American Z138.2, the Japanese JIS Z872 or the German DIN6164 [36]. In the ASTM D3131-97 standard [1] color and gloss tolerance practices are defined, while in the ASTM D2244-05 standard [2] practices for calculation of color tolerances and differences from instrumentally measured color coordinates are detailed. Particularly, in the ASTM D1535-14 standard [3], color specification through the Munsell system is formally described. This practice defines a simple visual method for color specification, which stands as an alternative to the method of CIE system, which is more precise, complex, and it relies on spectrophotometry. Color specification through visual mean is employed for recording and identifying colors limited to opaque objects (e.g., soils, minerals, flowers, or painted surfaces) [3]. Color specification is performed using Munsell charts. Each chart is made of a number of colored chips, with a fixed hue and several discretized chroma and value parameters. The number of charts depends on the edition of Munsell Soil Charts (e.g., 9 charts in the 2000 edition, 13 charts in the 2009 edition), while the number of chips depends on the chosen hue (16–42 per chart). Neurobiological researches stated that the reflectance spectra of color chips in Munsell charts matches the sensitivity of cells in the human eye that are responsible for color specification [11]; hence, they represent a valuable tool for color specification by visual mean. For this reason, they were widely employed in color specification of soil profiles, inorganic or organic materials, colored glasses and pottery, or paintings. These applications made them a perfect tool for archaeologists, which are used to employ them directly in the excavations. Colors of an archaeological artifact can be identified and recorded with different aims: classification and analysis of soils [23, 33, 39], stylistic and technological study of painted pottery, and to date artifacts to a specific time or culture [13].
The procedure of color specification by visual mean, using the Munsell soil charts, is also defined in the ASTM D1535-14 standard [3]. First, the two most similar hues to the specimen color have to be chosen by the user. Then, the selected chart is used as a mask, passing chip by chip over the specimen surface, and choosing the most similar chroma/value pair, eventually. A procedure of this kind is subjective (error prone), time consuming, and requires a hard copy of the Munsell soil charts (low affordability). Precision and accuracy of the procedure may be augmented repeating the color specification task more times and by different users. Indeed, the main issue is that color perception is strictly subjective [15]. Hence, one of the main aims of this work is to provide a tool for an objective and automatic color specification in the Munsell color system, to be used particularly in the archaeological research field. For this purpose, in our method we employed digital cameras for images acquisition. Pictures of specimens of soils have been used before in laboratory with controlled lightning conditions [4, 27, 31, 35–37]. All of these works followed the guidelines of ASTM D1535-14 standard for image acquisition [3, 28]: The light is artificially set to fixed values to know the standard illuminant (e.g., D55-mid afternoon light or D65-noon daylight), angle of view and distance of the camera from the specimen are measured and known, and an opaque background is used to avoid light reflection. Following these guidelines is difficult, potentially expensive, and time-consuming, as it requires specimens to be gathered and moved from excavations to a proper laboratory. Recently, we conducted new case-studies in a setting with controlled environment, and we contextually implemented a web-application version of ARCA, named ARCA 2.0 [41, 42]. However, one of the main aim of this work is to investigate the capability of a method for color specification through images acquired with affordable digital cameras and in an uncontrolled environment. In recent years, the growing popularity of mobile devices has brought along new methods for color specification in the Munsell color system and new research opportunities. High-definition cameras and sensors of certain smartphones has made more viable their choice of use. Gomez et al. [14] evaluated Munsell color specification task employing a mobile phone in a light box under controlled illumination conditions. Han et al. [18] specially designed two optical lenses, which are coaxial with the phone lens and are attached to the phone. Through these special lenses, they augmented the embedded Complementary Metal Oxide Semiconductor (CMOS) sensor, managing to acquire images with an adjustable view field, fixed shade, and calibrated colors. Several researches related to color specification have been conducted [6, 10, 12, 35–38], in which research groups investigated how color identification matters in artifact surface reconstruction, automatic and semi-automatic white balancing through Macbeth color checker, defect restoration, and aging estimation for pottery. However, in all of the above mentioned works the constant factor is always a controlled environment. With the term “controlled environment,” we refer to a scenario in which light values, illumination conditions, field of view, and distance between camera and specimen are fixed. In fact, methods using uncontrolled settings for image acquisition are still unavailable or incomplete. Thanks to our previous experience, in early 2017, we presented our first version of ARCA: Automatic Recognition of Color for Archaeology, a desktop application for Munsell estimation [24]. ARCA is a framework in which we implemented and improved our method. The pipeline of our application is very smooth: image acquisition of specimens, manual sampling of the image, color specification of the sampled points in the Munsell color system, and creation of a session report (Figure 1). ARCA framework is designed for archaeologists, taking into account that the system might help them directly in the archaeological site for the color specification task. We designed our pipeline using nothing but digital cameras leaving aside expensive materials as Munsell Soil Charts, Macbeth color checker or spectrophotometer can be, and without the constraint of a controlled environment for the photo acquisition phase. Attempting to face problems of color specification by visual mean (subjective, error-prone, time consuming), we developed in ARCA a feature for multiple selection and estimation of samples from the picture of specimens, to provide a way for estimation of Munsell notation in an objective, deterministic and fast way. However, color specification feature provided by ARCA may result useful even for scholars and users from a research field different from archaeology. For instance, color specification has been employed for investigation of food ingredients [20], resin composites in dentistry [16], food package printing [21], shading of paints [30], and quality assessment in industrial contexts [19].
In our first assessment of ARCA [24], we gathered in an uncontrolled environment the dataset named ARCA108, consisting of 108 images and 22,848 samples from Munsell soil charts 2000 edition. We compared all samples with Munsell reference values exploiting the CIEDE2000 ($Delta E_{00}$) color difference definition [2]. In this work, we extended the ARCA dataset, adding images from two new acquisition sessions. We acquired 156 images and 31,776 samples from the Munsell soil charts 2009 edition and 64 images and 1,536 samples from a real test case using 16 pottery shards. The reference ground-truth values for these fragments have been gathered by three archaeologists of the USF Department of History performing a standard color specification task by visual mean. Hence, in this work we are able to present and publish an extended version of ARCA dataset with 56,160 samples, named ARCA328, as it counts 328 images now, increased from the previous 108 [24]. Moreover, in Reference [24] we computed only CIEDE2000, while in this extension we added the computation of CIEDE1976 ($Delta E_{76}$) color-difference definition, as it is more suitable for visual differences perception evaluations [2]. CIEDE2000 and CIEDE1976 are compared, together with differences computed only on $L^{*}$, $a^{*}$, and $b^{*}$ channels. Through these extended evaluations, we will try to assess the soundness of our proposed method, to find the best configuration (the one with the minor error) of suggested device settings, and to highlight if there is any difference in terms of color tolerance when using a specific edition or sheet of the Munsell soil charts. Color tolerance is detailed in Section 3.2. To make our proposal comparable with other Munsell estimation methods and to consider accuracy problems, we use mean and standard deviation values in the evaluation phase [32]. Once more, our aim is to define a method for an objective and deterministic Munsell notation estimation, easy and fast to be used on site.
The article is structured as follows: in Section 2 the acquisition phase, validation phase, and ARCA desktop application will be described. The experimental results are given in Section 3, and then final remarks and considerations conclude the article in Section 4.
I'm looking at at document that describes the standard colors used in dentistry to describe the color of a tooth. They quote hue, value, chroma values, and indicate they are from the 1905 Munsell description of color:The system of colour notationdeveloped by A. Munsell in 1905identifies colour in terms of threeattributes: HUE, VALUE (Brightness)and CHROMA (saturation) HUE (H): Munsell defined hue as thequality by which we distinguish onecolour from another. He selected fiveprinciple colours: red, yellow, green,blue, and purple; and fiveintermediate colours: yellow-red,green-yellow, blue-green, purple-blue,and red-purple.
These were placedaround a colour circle at equal pointsand the colours in between thesepoints are a mixture of the two, infavour of the nearer point/colour (seeFig 1.).VALUE (V): This notation indicates thelightness or darkness of a colour inrelation to a neutral grey scale,which extends from absolute black(value symbol 0) to absolute white(value symbol 10). This is essentiallyhow ‘bright’ the colour is.CHROMA (C): This indicates the degreeof divergence of a given hue from aneutral grey of the same value. Thescale of chroma extends from 0 for aneutral grey to 10, 12, 14 or farther,depending upon the strength(saturation) of the sample to beevaluated.There are various systems forcategorising colour, the Vita systemis most commonly used in Dentistry.This uses the letters A, B, C and D tonotate the hue (colour) of the tooth.The chroma and value are bothindicated by a value from 1 to 4.
A1being lighter than A4, but A4 beingmore saturated than A1. If placed inorder of value, i.e. Brightness, theorder from brightest to darkest wouldbe:A1, B1, B2, A2, A3, D2, C1, B3, D3,D4, A3.5, B4, C2, A4, C3, C4The exact values of Hue, Value andChroma for each of the shades is shownbelow So my question is, can anyone convert Munsell HVC into RGB, HSB or HSL? Hue Value (Brightness) Chroma(Saturation) 4.5 7.80 1.72.4 7.45 2.61.3 7.40 2.91.6 7.05 3.21.6 6.70 3.15.1 7.75 1.64.3 7.50 2.22.3 7.25 3.22.4 7.00 3.24.3 7.30 1.62.8 6.90 2.32.6 6.70 2.31.6 6.30 2.93.0 7.35 1.81.8 7.10 2.33.7 7.05 2.4They say that Value(Brightness) varies from 0.10, which is fine. So i take 7.05 to mean 70.5%.But what is Hue measured in? I'm used to hue being measured in degrees (0.360).
But the values i see would all be red - when they should be more yellow, or brown.Finally, it says that Choma/Saturation can range from 0.10.or even higher - which makes it sound like an arbitrary scale.So can anyone convert Munsell HVC to HSB or HSL, or better yet, RGB? The hue specification you've given here is incomplete (4.5 should be 4.5Y etc). Since the link is dead, if anyone is interested, the specs are still alive here:The only free utility for Munsell conversion I could find was this:Very old as you can see, but seems to work well.
Current programs that can do this are not free:. (this one has a free 14 day trial)The current holders of the Munsell products are, they probably have some conversion solutions as well.Further, note that the link you supplied includes definitions for the same colors in other color coordinates - namely Yxy and CIE l ab. Both can be freely converted online at or offline with this. It is rather involved. The short answer is, converting Munsell codes into RGB involves interpolation of empirical data in 3D that is highly non-linear. The only data set that is publicly available was collected in the 1930's.
Free or inexpensive programs that I have found on the net have proved to be flawed. I wrote my own. But I am jumping ahead. Let's start with the basics.Munsell codes are different in kind than those other codes, xyY, Lab, and RGB. Munsell notation describes the color of an object - what people experience when they view the object.
(Isaac Newton was the first to realize that color is in the eye of the beholder.) Munsell conducted extensive experiments with human subjects and ingenious devices.The other codes, i.e. XyY, L ab., and RGB, describe light that has bounced off an object and passed through a convolultion with a rather simple mathematical model of a human eye. Some google-terms are 'illuminant,' 'tri-stimulus,' and 'CIE standard observer.' Munsell describes the colors of objects as they are perceived under a wide variety of illuminants. Another google-term is 'chromatic adaptation.' Chromatic adaptation in the brain is automatic if the lighting is not too weird. It is really quite remarkable.
Take a piece of typing paper outside under a blue sky. The paper looks white.
Take it indoors and look at it under incandescent (yellowish) lights. It still looks white!
Munsell tapped into that astonishing processing power empirically. Munsell codes also preserve perceived hue at different chromas.
A sky-blue and a powder-blue that Munsell assigns the same hue notation, e.g. 5RP, will appear to the typical human with normal eyesight to be the same hue. More on that in the footnote.CIE xyY, L ab., and RGB mean nothing unless an illuminant is specified. Chromatic adaptation for illuminants in the mathematical model is computationally difficult. (Rough but simple approximations can be done using the 'Bradford matrices.' ) The RGB that we use is by default 'sRGB,' which specifies an illuminant called D65.
D65 is something like a cloudless day at noon. The Lab numbers listed by the OP are probably relative to D50, which is more like afternoon or morning light. The xyY numbers might be relative to D50, or they might be relative to an old standard called C. I am not going to check. C was the light from a standard lighting fixture that was relatively inexpensive to build in the 1930's. It is obsolete. But C plays a key role in the answer to the question.In the 1930's, color scientists were developing the mathematical models.
One of the things they did was to take a standard Munsell Book of Color, shine illuminant-C light on the colored chips in the book, and record the data in xyY format. Prison break season 4 torrent. That data-set, called the 'Munsell Renotation Data,' is the only one that is freely available. Others surely exist, but they are closely held secrets.Good news though. The data set works good.
The Munsell authority today is a company called Gretag Macbeth. I imagine they have voluminous data related to the color-chips they sell.
The only numbers I know of that they publish are the D50 Lab and D65 sRGB numbers for a small set of colors on their cards. I wrote an interpolator based on the old renotation data. It agrees with the numbers for the Color Checker card almost exactly. I regret to inform that so far I have only written code for the conversion that goes the opposite direction from what the OP requested (a year ago, as I type this). It goes from sRGB to Munsell. I click on an image, and the program displays the sRGB and Munsell notations for the area clicked upon. I use it for oil painting.Footnote: CIE has a standard that is analogous to Munsell.
Practical applicationsThe objective of FlightGear and of all the volunteers that collaborate in its development is to offer a valid framework for academic use and investigation tasks. It's ideal to train pilots, as a tool for aeronautical engineers and for anyone else interested, even for pure entertainment.
It is called LCh subscripted with a,b. It is L ab. in polar coordinates.
The hues are in degrees. Chroma numbers are approximately 5 times the C in Munsell HVC. LCh has its problems though. If you have ever used a photo editor to pump up the vividness of the sky, only to see the blue turn to purple, the program was probably using LCh.
When I started writing my program, I was unaware that Bruce Lindloom had done work that parallels what I was doing. Was invaluable to me as I finished the project.
He designed a space he calls UPLab, which is LCh straightened out to align with Munsell. I had already re-invented LCh and (essentially) UPLab before I discovered Mr. Linbloom's site, but his knowledge of the subject far exceeds mine. Munsell Renotation System to sRGB Colourspace Conversion, our open source Python colour science package allows to perform that conversion. I'm late to the party, but I found another resource that may be useful on this topic.Someone at the 'Munsell Color Science Laboratory' dug up some 1943 data from Munsell, all based on 1930s Munsell research:The page refers to an Excel spreadsheet with the 'real colors only' subset of the data that falls within the 'Macadam limit', which appears to mean the gamut of colors that can actually appear on reflective surfaces. The spreadsheet link doesn't work, however, but on a hunch I guessed that it left out one level of the directory tree. I tried the URL - and it worked.
(I wouldn't be surprised if the owner of the site eventually notices it, and fixes the link, which is likely to break my link.)I messed with that spreadsheet a little to get it to generate HTML to show me the RGB colors, and added these cells to the spreadsheet:.