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].

Munsell DG allows you to browse the Munsell color space on your iPad, iPhone or iPod Touch. Touch Munsell colors to see their RGB values.

Universal's records are long gone, but some information has been collected from serial numbers and configurations of known guns. Thanks to John Blood for providing the serial number info. If you have a Universal M1 Carbine, especially one with a SN in the transition ranges listed below, or examples that don't fit the range, please send the. The highest Universal serial number observed so far has been 488,363. A separate set of serial numbers was used for the Vulcan model carbines produced 1963-1965. Vulcan serial numbers recorded so far have been 1014 - 2453. During 1980 Universal produced a commemorative carbine. Serial numbers recorded so far have been 00204 - 000430. M1 carbine universal serial numbers. Serial numbers between approx. 130,000 and 299,999: If you own a Universal Firearms.30 caliber Carbine within this serial number block it is strongly recommended you examine and continue to examine the barrel in the area of the gas piston for any damage to the barrel. If you find even a small amount of damage do not fire the weapon.

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.

With HEX/RGB Color Converter, you can easily convert color from HEX value to ARGB value, and vice versa. Additionally, you can easily copy these values to Clipboard. The conversion happens automatically when you finish typing with key 'Enter' or clicking anywhere else, so that you don't have to do any extra move.With the color preview panel in the bottom, it is very handy to use HEX/RGB Color Converter in snapped mode when you are working on some UX related work.All windows modes and rotations are supported.Have fun! With HEX/RGB Color Converter, you can easily convert color from HEX value to ARGB value, and vice versa. Additionally, you can easily copy these values to Clipboard. The conversion happens automatically when you finish typing with key 'Enter' or clicking anywhere else, so that you don't have to do any extra move.With the color preview panel in the bottom, it is very handy to use HEX/RGB Color Converter in snapped mode when you are working on some UX related work.All windows modes and rotations are supported.Have fun!Show More.