For a long time, colour management was only seldom used in large-format printing. Sign shop personnel would linearize and then send their cyan, magenta, yellow and key/black (CMYK) jobs to their digital printers. As such, they relied on these devices’ printable gamut, but this led to issues with colour consistency and repeatability.
长期以来，在宽幅图形打印中忽视对色彩的管理，打印店的员工只会运用青色、品红、黄色和黑色，久而久之他们就只依赖于这些打印范围，导致了宽幅打印的颜色出现了一致性或重复性的问题。
More recently, colour management has gone mainstream in large-format printing, as it is seen to provide a lot of benefits to both print service providers (PSPs) and their customers. There is more than one way to implement it, however, depending on the approach a shop takes to standardization.
最近，宽幅打印开始重视对色彩的管理，因为这样做，能为标识服务行业的供应商以及他们的客户带来更多好处。然而，对色彩的管理的方法不止一种，这取决于标识打印店制定的标准化管理。
Standardizing colour management
标准化色彩管理
The operation of a large-format inkjet printer depends on a raster image processor (RIP). RIPs are always set up with printer profiles, which include ink limits, linearization and, optionally, an International Color Consortium (ICC) profile. When graphic files are submitted to the RIP, the input colours—whether CMYK or red, green and blue (RGB)—are converted to the printer’s output colours, based on tagged image and file elements of the input profiles.
在打印机进行操作时，光栅图像处理器的运用非常重要。光栅图像处理器是打印机的配置，包括油墨限制、线性化、还有一个颜色组合的文件夹。当图形文件提交到RIP文件时，输入的颜色不管是红色、绿色还是蓝色，都会被转换为打印机的输出颜色。
This is the standard colour management process, but numerous problems are associated with it, as follow.
这是其中一种色彩管理的方法，当然，这种方法也是存在一些问题，需要我们注意。
Colour differences
色差
Printed colours may appear different than intended, particularly if the input profile used within the print shop does not match the profile the original designer used. If an image has text layered on top of it, for example, and the colour of the text is derived from a part of the image, then when the file is processed, any change to the profile or intent of the image will also change the colour relative to the text, in a way the designer likely did not intend.
如果在打印时使用的配置文件与原始设计师使用的配置文件不匹配，打印出来的颜色可能跟预期的会有所不同。例如，如果一个图像的文本添加了分层，而文本的颜色是从图像的一部分派生出来的，那么在处理该文件时，设计者对图像的内容也要更改成与文本相匹配的颜色。
Applying different profiles and/or render intents to different elements, such as ../images and vectors, can also significantly affect their printed appearance.
不同的配置拥有各自独特的应用元素，不同的图像和印刷技术，也会影响打印外观。
Overprints, transparencies and blends
叠加式的打印的透明度和混合度
Applying profiles can dramatically change overprinting elements. When converting the cyan and magenta (C+M) elements from the General Requirements for Applications in Commercial Offset Lithography (GRACoL) profile to the printer profile, for example, the conversion may result in not only C+M, but also a bit of black (K), due to the printer profile. At this point, any underlying black text would disappear, because K was generated in the C+M overprinting elements.
应用配置文件可以极大地改变覆盖元素。例如，将cyan和紫红色(c+m)元素从商业平版印刷(GRACoL)配置文件转换为打印机配置文件时，转换可能不仅会导致c+m，而且由于打印机受配置文件的影响，也会导致出现一些黑色的印记，此时，任何底层的黑色文本都会消失，因为K是在c+m超打印元素中生成的。
Colour differences can also occur with transparencies, as elements that would blend might end up being converted using different rendering intents. Overprints can seem to disappear and blends can
look different when assigning profiles.
使用“透明度”选项也能使图像产生色差，各自元素可能会根据不同的呈现意图进行转换，在分配配置文件时，叠加式印刷的效果也会不同。
Colour mismatches
颜色不协调
Perceptual intent changes all colours in a file, not just those that are out-of-gamut. So, colours might look very different, depending on whether they are converted to a standard such as GRACoL or to the printer profile. The same job printed on multiple machines will look very different, since the gamut of those devices will differ and the perceptual intent adjusts all colours to the printer’s output profile.
专业人员常常想要改变文件中的所有颜色，不仅仅是那些外域的颜色。由于打印设备的范围不同，同一份打印成果在多台机器上操作也是不同的，而感知意图是将所有颜色调整到打印机的输出配置文件中。
Spot colours
专色
Undefined spot colours are printed using an alternate space, usually CMYK. If the designer has taken this into account, then the results might look very different, due to the same reasons cited above for colour differences.
未定义的专色使用不同的打印格式，通常为CMYK。如果设计人员考虑到这一点，那么结果可能看起来会不一样。
By way of example, Figure 1a (right) shows the output of a document created using Adobe Illustrator graphic design software, comprising an RGB image of an acorn, an embedded standard RGB (sRGB) colour space profile, a grey background sampled from the image, text with colour sampled from the image and another gradient derived from the same colour.
作为示例，图1a（右）显示了使用Adobe Illustrator图形设计软件创建的输出文档，包括RGB图像、标准RGB颜色轮廓。图像从灰色背景采样 ，抽取颜色的文本从相同颜色派生到另一个颜色。
Figure 1b shows what happens when the designer’s intent is ignored—likely unintentionally and relying on default application settings. A colour difference appears, for example, because the background is defined in CMYK without a profile. Adobe Illustrator would have defined the CMYK from the grey of the sRGB space and converted it to the Specifications for Web Offset Publications (SWOP) profile, i.e. the designer’s working space. If the combination of profiles and rendering intents assigned to the image and the background is not exact, then such a colour difference will appear.
图1b显示了当设计者的意图被忽略的时候，依赖于默认的应用程序设置。例如，由于背景是在没有配置文件的CMYK中定义的，所以出现了颜色差异。Adobe Illustrator将从sRGB空间的灰色中定义CMYK，并将其转换为Web偏移出版物(SWOP)概要文件的规范。如果分配给图像和背景的概要文件和呈现意图的组合不精确，那么就会出现这样的颜色差异。
Further, the acorn became brighter and more saturated compared to the rest of the design. This is because it was mapped directly to the printer gamut. This is a desirable result, but breaks the match between the text and the gradient colours in the design. The gradient is defined by an overprinting spot colour. The background now has two different appearances, also seen in the overprinting and blending effects.
此外，与其他设计相比，橡果变得更加明亮和饱和。这是因为它被直接映射到打印机的所有域，但是在设计中打破了文本和渐变颜色之间的匹配。渐变色的彩色文本是由一种覆盖的斑点颜色来定义的，背景现在有两种不同的外观，同时出现在印刷和混合效果中。
Finally, Figure 1c shows what happens when the spot colours are replaced as RGB or CMYK before being RIP’d or when the overprint is turned off to counter the gradient effect in Figure 1b. The text no longer overprints, as its colour has been replaced with a CMYK version that represents the spot colour. The CMYK match is very accurate, but due to the overprinting effect, the spot colour is darkened by the grey background.
最后，图1c显示了当斑点颜色被替换为RGB或CMYK，图1b中关闭了覆盖的渐变效果时，出现的问题，这时的文本不再被覆盖，因为它的颜色已经被CMYK所取代，灰色背景使斑点颜色变暗。
The gradient no longer shows the correct overprinting effect. The original spot colour was a duotone, fading to zero of another spot colour. As a result, it has nicely blended away. Now, however, due to either turning off the overprint or replacing the spot colours with their CMYK equivalents, the overprinting blend is lost and blends to white. Any change made to the original design by assigning or removing embedded profiles, disabling overprints or replacing spot colours before RIP-based blending will result in ‘broken’ output.
此时，渐变色的彩色文本不再显示正确的覆盖效果。最初的斑点颜色是一种双色，它能在另一种颜色上逐渐消失。这种情况的出现，是因为要么关闭了覆盖的印刷体，要么用了CMYK的替代品取代了它。对原有设计进行的任何更改，通过删除嵌入式配置文件，导致了“断开”的效果输出。
With all of this in mind, one may well wonder, why use colour management at all? The alternative of not using it, however, means sending a design file’s CMYK data directly to the printer via linearization, which results in the least colour consistency, so it is definitely not recommended. Rather, the better approach is to use standardized printing.
考虑到出现的这些问题，更加要重视色彩管理了。此外，通过线性化将设计文件的CMYK数据直接发送到打印机上，能有效地避免颜色一致性问题的出现，另外，使用标准化的打印模式也能有效避免这些问题。
Standardizing printing
标准化打印
The goal of standardized printing is to reduce the colour deviations and variations in graphics produced by different devices. These differences usually exist because machines vary in their colour capabilities—sometimes quite dramatically—due to a variety of printhead technologies, ink formulations and substrates.
标准化印刷的好处是能减少不同设备产生的色彩偏差和图形变化。有时因为机器的色域不同，有时由于使用了不同的打印头，或者墨水配方和底物不同，都会导致色差产生。
Standardized printing also respects the designer’s intentional (or unintentional) overprint, transparency and blend effects by converting colours correctly to a standard before the conversion to the printer’s own colour space. This approach ensures the output is accurate and uses everything the printer’s gamut has to offer. As there is no need to test the printer to see if the job will be handled correctly, this saves time for the operator who is preparing and printing the job.
标准化印刷也为设计者的意图所制定的，包括叠加式印刷、透明和混合效果。在转换到打印机的色域之前，需要将颜色格式正确地转换为标准化印刷格式，这种方法保证了输出的准确性。
The way to standardize printing is to convert all incoming colour spaces—whether CMYK or not—to a chosen reference profile first, like GRACoL, and only thereafter to the printer profile. Thus, all of the colours are first matched to a standard, then converted with the printer’s specific capabilities in mind, which helps maintain overall colour appearance between different devices.
标准化打印的方法是把所有的色域都转换成一个选定的参考配置文件，比如GRACoL，然后再到打印机的配置文件。因此，所有的颜色首先改成一个标准，然后再用打印机的特定功能进行转换，这样助于保持不同设备之间的整体色彩外观。
A subset of the International Organization for Standardization’s (ISO’s) Portable Document Format (PDF) specification known as PDF/X was developed for this reason, among others. PDF/X files contain the reference output intent with which they should be processed, so as to deliver a single job with everything embedded. In any PDF/X3 file (or a more recent version), all of the elements that do not match the output intent’s colour space must be tagged with ICC profiles to ensure correct colour conversions.
pdf/x文件包含了引用输出意图，包含所有工作内容。在任何pdf/x3文件(或最近的版本)中，所有与输出意图颜色空间不匹配的元素都必须使用ICC的配置文件进行标记，以确保颜色的正确转换。
This file format is now broadly supported by mainstream software applications, including Adobe Illustrator and InDesign, making it very easy to specify how a sign shop’s customers should supply their jobs in the first place. They can also be pre-flighted very easily to ensure they are acceptable before printing. The files should be exported to the most recent version of PDF/X available.
现在，这个文件格式得到了主流软件应用的广泛支持，包括Adobe Illustrator和InDesign，文件可以导出最新版本的pdf/x版本。
This approach to standardizing converts all elements to a single colour space by way of reference profile and supports spot colours. The use of device-link profiles becomes unambiguous, as there is only one colour space after the process of standardization.
这种方法将所有的元素转换为一个单一的颜色空间，由于标准化过程之后只有一个色域，设备链接配置文件使用起来会变得很简单。
Indeed, the use of device-link profiles is far superior to typical ICC conversions. By allowing a workflow to calculate a direct link, it delivers the following advantages:
使用设备链接的配置能提供以下优点:
Ink savings
墨水的储蓄
Device-link profiles can maintain detailed midtones and shadows while saving significant quantities of ink. In addition to reducing overall costs, this extends the longevity of printheads, improves printability on various types of media and saves energy by enabling printing at lower temperatures.
设备链接配置文件可以在节省大量油墨的同时，还能保持图像的色调和阴影部分。除了降低整体成本外，还能延长图像的寿命，此外，还能在较低的温度下打印来节省能源。
Repeatability
重复性
The device-link profile contains information about which colour targets it needs to hit and how to direct a specific printer to return an image to its original state.
设备链接文件包含了需要点击哪些目标颜色的信息，还能引导特定的打印机如何将图像返回到原始状态。
In practice, this means when a printer’s colours start to ‘drift,’ a simple print-and-measure process—with a relatively small colour target, involving approximately 500 patches for a CMYK printer, read with a spectrophotometer—can compensate. This means the printer will produce the same output result, day after day, without much external effort.
当打印机的颜色开始“漂移”时，在简单的打印和测量过程中，会有一个相对较小的色彩目标，包含大约500个CMYK打印机的补丁，这意味着打印机将日复一日地生成相同的输出结果。
Keeping as much colour as possible
尽可能多保留原有颜色
There is a common misconception that using a reference space will necessarily limit the capabilities of the printer to the common colour spaces shared by that reference and the printer’s own gamut. This is not always true, however, as there are several strategies that can also be implemented after a file passes through the standardization process:
有一种常见的误解，认为使用参考空间一定会限制打印机的功能，影响打印机的的色域。这并不是完全正确的，因为有些操作可以在一个配置文件里通过标准化格式来实现:
Spot colour mapping
专色的映射效果
Spot colours will be mapped to the printer’s gamut and not be limited by the reference output intent. A job using GRACoL as the reference and two Pantone colours, for example, will actually be rendered as a six-channel job, i.e. CMYK plus two spot colours. This method ensures all blending and transparency effects—like drop shadows and overprints—are processed correctly, while enabling the RIP to address the full gamut of the printer.
点色将被映射到打印机的所有范围，而不受参考输出意图的限制。例如，使用GRACoL作为参考和两种普通色彩，即CMYK+2。这种方法保证了所有的混合和透明效果，阴影和超打印都能合理运用，同时也能使打印机的全部内容都能被打印出来。
Gamut mapping
色域映射
The reference colour space—usually CMYK—can be mapped to the printer gamut in any way that is preferred. In some cases, for example, ‘punchy’ colours may be prioritized over printer-to-printer consistency or matching to a contract proof.
参考色通常可以以任何方式被映射到打印机的范围。例如，在某些情况下，“punchy”的颜色可能会优先于其他颜色。
If the printer’s gamut is broader than the reference space, then perceptual mapping with black (K) compensation can expand the reference space and maximize the use of the printer’s gamut. If, on the other hand, the printer’s gamut is smaller than the reference space, then a hybrid approach of perceptual and colorimetric mapping is recommended. By keeping the colorimetric mapping within the achievable ‘middle part’ of the gamut and using the perceptual mapping to compress the edges of the gamut, a visually comparable image can be retained without flattening the edge colours.
如果打印机的色域范围大于参考空间，那么带有黑色补偿的感性映射就可以扩展参考空间，并最大化地使用打印机的所有域。另一方面，如果打印机的色域比参考空间小，那么推荐使用一种感性映射和比色映射。通过将色度的映射保持在可实现的“中间部分”范围内，并使用感知映射来压缩色域的边缘，可以保留一个视觉上的对比度，而不会使边缘色消失。
RGB referencing
引用RGB
For fine art reproductions and photography, an RGB reference space may be used, so as to deliver a broad gamut without separating the image to CMYK, where there could otherwise be breaks in smooth transitions.
要达到很高的像素效果，可以使用一个RGB参考空间，以便在图像没有被分割成CMYK的情况下提供一个宽广的范围，否则颜色可能会出现裂痕。
After this type of standardization, the image can be mapped to the printer gamut. This way, the image benefits from both standardization and device linking.
在这种类型的标准化之后，映像可以映射到打印机的范围。这样，图像就会从标准化和设备链接中得到很好的效果。
A better way
更好的办法
The advantages of standardized printing are significant for the production of wide-format graphics. The key is to choose a RIP that is capable of (a) supporting the standardized printing process for inkjet devices—without the limitations most RIPs face due to their approach to standardizing colour management—and (b) using device-link profiles. The rewards are worth the investment.
标准化打印对于制作宽幅图形是非常重要的。关键是选择一个能够支持标准化打印格式的喷墨设备，因为他们具有标准化颜色管理和设备链接的配置文件，而不受很多条件限制。
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