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反射式Colorchecker测试卡

常用的反射式Colorchecker测试卡(配合反射光源使用)

透射式Colorchecker反射式Colorchecker

ColorChecker目标旨在实现逼真的影像再现,这样摄影师可预测和控制色彩在任何光源下显示出来的实际色彩。24 种色彩中的每一种色彩都代表了自然物体的实际色彩,并且每种色彩都能反射光,犹如其真实世界的对应物一样。

色彩数量: 24 种自然物体色,彩色、原色和灰度色。

色彩描述: 白色、黑色、四种中性灰色、蓝色、绿色、红色、黄色、品红、青色、橙色、紫蓝偏紫、中度红色、紫色、黄绿和橙黄、深肤色、浅肤色、天蓝色、树叶色、蓝花色和蓝绿偏蓝

色度数据

大小:

- ColorChecker(标准型):8.25 x 11 英寸(21.59 x 27.94 厘米)

功能:

ColorChecker® 24 色卡目标是在众多色彩中一系列经科学配制的 24 个自然色、彩色、原色和灰度色块。这些色块大多代表自然物体,如人体皮肤、树叶和蓝天。由于它们代表各自对应物的色彩,并且以同样的方式反射所有可见光谱中的光,所以这些色块可在任何光源下与其代表的自然物体的色彩相匹配,同时还可用于任何色彩再现流程。ColorChecker 还可用于数码相机创建白平衡,以确保在任何光照条件下都可产生准确、均匀的中性白。

要比较数码照片和真实景色或测试目标,如果您拍摄的是 JPEG 图像或传统图像,只需第一张照片拍摄 ColorChecker 即可,如果您拍摄的是 RAW 图像,可在拍摄期间随时拍摄 ColorChecker。然后,您可到工作室使用拍摄的 ColorChecker 照片在任何色彩还原系统中比较、评估和分析色彩再现中的差异。该客观标准将有助于您避免代价高昂的错误以及反复的色彩校正试验。

ColorChecker应用领域包括:

(1)数码摄影:检查图像,校正白平衡并执行色彩校正;

(2)传统摄影:检查胶片、光线、滤色器和纸张;

(3)印艺:检查任何打印或者打样程序;

(4)电影(电视和视频):检查相机、光线和胶片;

如果您要为您的数码相机创建色彩配置文件,并想要将数码摄影提高一个档次,那么请考虑使用 ColorChecke24色卡 

Colorchecker 参数数据介绍

1. X-Rite default old:
Color space Wt Pt

(the default setting
prior to 4.4)

This section has been rewritten to reduce confusion.

L*a*b* values provided by GretagMacbeth in 2005. The values are in an Excel file, Lab data Iluminate D65 & D50 spectro.xls (click on the link to open or download), that contains 2 degree D65 data used for D65 color spaces and 2 degree D50 data used for D50 color spaces. This is somewhat different from the current practice of always assuming L*a*b* data was obtained with a D50 illuminant and converting it to D65 (for D65 white point color spaces– sRGB, Adobe RGB, etc.) using a Bradford Transform. The 2 degree D50 data is still in the X-Rite Colorchecker data page (as of March 2016), even though X-Rite has announced changes to the reference values for Colorcheckers manufactured after November 2014). Starting with Imatest 4.4 (March 2016), the reference selection includes another option, X-Rite default: pre-Nov 2014 D50 (described below), that uses the D50 data and converts it to D65 for color spaces with a D65 white point (sRGB, etc.).

2. Babelcolor

L*a*b* values measured by Danny Pascale of Babelcolor, from Table 2 (bottom) of RGB coordinates of the MacBeth ColorChecker, which is recommended reading for all Colorchecker users. Pascale’s D50 values are transformed to D65 using the Bradford transformation for color spaces with a D65 white point.

3. Danes-Picta BST4D

A knockoff of the Colorchecker (same geometry with different colors) from Danes-Picta in the Czech Republic (on their Digital Imaging page).
4. LAB file
(CSV or CGATS;
no transforms)
Read a file (CSV or CGATS format) containing L*a*b* data. The reference illuminant is assumed to be the same as the selected color space (D65 for sRGB, etc.). This is at variance with current practice, where L*a*b* files are assumed to have D50 data. The new LAB D50 file (below; Imatest 4.4+) is now recommended.
A dialog box appears for entering the filename. CSV files consist of 24 lines with L*, a*, b* values on each line separated by spaces, commas (,), or semicolons (;). Example (first 3 lines of 24):
38.08, 12.09, 14.39
66.38, 13.22, 17.14
51.06, 0.38, -22.06
(The commas are optional if spaces are present & vice-versa.) If you have an Excel .CSV file with extra rows or columns, you can easily edit it Excel by selecting the key region (3 columns, 24 rows), copying it to a new file, and saving it in .CSV format. L*a*b* data is preferred to xyY data below because it is independent of white point color temperature, hence less error-prone. The CGATS file format is also supported.
5. xyY 5000K file,
6. xyY 6500K file,
7. XYZ 5000K file,
8. XYZ 6500K file
Read a file containing xyY or XYZ data with a 5000K (D50) or 6500K (D65) white point. Procedure and format is the same is the LAB data file, above. These are generally not recommended: they are kept for backwards compatibility.
9. Last file (none or
file name)
Displays the last selected reference file (LAB, xyY, or XYZ). Select to read this file.
10. X-Rite default:
pre-Nov 2014  D50
(new in Imatest 4.4+)
X-Rite L*a*b* D50 data for charts manufactured before November 2014, linked in the New color specifications…page, and still found on the X-Rite Colorchecker data page (as of March 2016) . Converts it to D65 for color spaces with a D65 white point (sRGB, etc.). Note that the RGB values obtained from this data do not agree with the values on the X-Rite page. Danny Pascale evidently ran into the same problem. Table 2 (top) of RGB coordinates… has two RGB columns, labeled sRGB (Pascale’s calculations) and sRGB (GMB) (from the X-Rite Colorchecker data page). ThesRGB column is in agreement with Imatest sRGB values.
11. X-Rite default:
post-Nov 2014  D50
(new in Imatest 4.4+)
New X-Rite L*a*b* D50 data for charts manufactured after November 2014 from the New color specifications… page. Note that the CGATS files in these pages are in column-wise format, and can’t be read directly by Imatest. The post-November 2014 file uses commas (,) for decimal points.
4. LAB D50 file
(CSV or CGATS)
(new in Imatest 4.4+)
Read a file containing D50 L*a*b* data, and transform it if needed (using a Bradford Transform) to white point the selected color space’s white point. This is the recommended approach if you have spectrophotometer measurements for your individual chart. The CSV format is described above.

Reference file values can be

  1. measured on your own instruments (instructions here),
  2. derived from measured values from a camera you determine to be a “gold standard” by running Multicharts, then pressing FileSave L*a*b* results as CSV reference (making sure to check CSV reference file of L*a*b* results…). This can be useful for manufacturing testing because the camera under test is compared with attainable values rather then unattainable ideal values.
  3. values you have determined to be “pleasing” that you wish to use as design targets. (Remember, accurate color is not necessarily pictorially pleasing. Designers of consumer cameras often aim for “pleasing” colors, which typically involves increasing saturation in foliage, skies, and skin.)

Color space: You can select among the following. Danny Pascale’s A Review of RGB Color Spaces is recommended for readers interested in an in-depth explanation of color spaces.

sRGBThe default space of Windows and the Internet. Limited color gamut based on typical CRT phosphors. Gamma = 2.2 (approximately), White point = 6500K (D65).
Adobe RGB (1998)Medium gamut, with stronger greens than sRGB. Often recommended for high quality printed output. Gamma = 2.2, White point = 6500K (D65).
Wide Gamut RGBExtremely wide gamut with primaries on the spectral locus at 450, 525, and 700 microns. One of the color spaces supported by the Canon DPP RAW converter. 48-bit color files are recommended with wide gamut spaces: banding can be a problem with 24-bit color. Gamma = 2.2, White point = 5000K (D50).
ProPhoto RGBExtremely wide gamut. Gamma = 1.8, White point = 5000K (D50). Described in RIMM/ROMM RGB Color Encodings by Spaulding, Woolfe and Giorgianni.
Apple RGBSmall gamut. Used by Apple. Gamma = 1.8, White point = 6500K (D65).
ColorMatch RGBSmall gamut. Used by Apple. Gamma = 1.8, White point = 5000K (D50).
Rec. 709 LegalSmall gamut. Used in HDTV. Pixel values 16-235.
Rec. 709 FullSame as Rec. 709 Legal, but with Pixel values 0-255.
ACESAcademy Color Encoding System, used in the workflow developed by the folks who bring you the Oscars. Extremely large gamut, covering all visible colors. Linear gamma. White point = 6000K.
Rec. 2020 LegalFairly large gamut, covering most colors from reflected objects. For UHDTV. Pixel values 16-235.
Rec. 2020 FullSame as Rec. 2020 Legal, but with Pixel values 0-255.
DCI-P3Medium gamut, similar to Adobe RGB. For digital projection systems.

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