Good calibration and profiling software will provide a wide range of calibration target settings which are used in order to tune and optimise screen appearance, these options are vital since e.
Output profiles are a type of device colour space. Options such as resolution and media type can all affect output, so must be optimal. Next, test prints of a relevant set of colour patches are made, using the chosen software settings and using the correct paper and ink. After drying, accurate measurements of the test prints are made using a high quality spectrophotometer device. Next, these measurements are analysed within the profiling software and, in a process of assessing both the measured patch values and the target reference data, the software can produce an accurate device characterisation - an ICC output profile.
Now, Adobe Photoshop, and other colour management capable programs, can use this ICC profile to adjust image data, as it is sent to the printer. This means that we can expect an accurate reproduction of the original image file, within the limits of gamut of the printer and paper chosen.
An ICC printer profile is specific to one certain printer, one type of paper, one inkset and, even, to one print resolution and media setting. If you buy a different make of ink or type of paper, or alter software settings, then the printer will likely behave differently, this inevitably means that the profile we made will no longer describe the printed behaviour.
So, now, the process of printing using the ICC profile fails to give an accurate printout. A new profile would be needed in order to assess the printer's new behaviour. The need for consistency is often called "process control". Because of the importance of consistency, it is not a good idea to use low cost "compatible" ink cartridges when profiling, because the vital continuity of performance using those inks is very unlikely - due to poor quality control, they often differ, one to the next.
As well as on-site profiling, we also offer remote inkjet profiling, here. Good printer profiles can also be used within colour management savvy applications like Adobe Photoshop for on-screen softproofing in order to predict printed output. Softproofing means that a screen preview, simulating the output of a printer, can be viewed during image optimisation. Of course, accuracy in softproofing relies entirely on having a decent quality, well calibrated and profiled, display system as well as a good accurate output printer profile.
In a very similar process to that outlined above for inkjet printers, i. However, it is important to understand that profiling a press properly is quite a big task. It's very important to analyse a press for profiling in a well optimised state, that can take a lot of time. There is no "just use CMYK" any longer, each press type and paper type has it's own ink recipes and those are respected in the freely available standards based profiles.
So, there is a more practical way to work than by than profiling each press individually. What is on the plates is easier to work with which makes for faster more efficient use of the machine.
Standards based ICC profiles result from standard press runs measured by technical experts - "standard" press ICC profiles are available freely. More information about pre-press and standards based working here. Checking ICC profile accuracy, a high quality well controlled visual test is the ultimate way I feel more on testing display and print profiles here. Once a profile is associated or "assigned" in Photoshop terminology , then the relationship between the file's numbers and human vision is established.
That's because the actual colours of the constituents, Red Green and Blue are not defined. By associating a colour space definition, i. The data can now be a passed off to a display screen or to a printer in a process that uses those exact colour definitions - terminating in a conversion to optimise the data for the receiving device. So, what are they? These colour spaces define colour using a full scale, based upon how humans see colour, so that a particular set of values always means the same colour.
XYZ : Y is luminance. Z and X are related to human cone response curves. There are lots of papers online for those who'd like to delve further but that's certainly not needed in a quest to better understand how ICC profiles work in practice. Even a working colour space like AdobeRGB Some ICC profiles do contain quite a few tables to allow for conversion using different rendering intents, but, basically, all those tables do is to provide for variants on the above calculations.
Liken this to translating a word from French to German without access to a French to German dictionary. When a conversion between two colour spaces takes place we are normally offered a choice of rendering Intent. For output conversions all the intents, Perceptual, Relative Colorimetric, Absolute Colorimetric and Saturation are all available within the process and will affect the result. However, when converting from an input colour space to working space, although Photoshop offers the options above, all that's actually available is a form of Colorimetric rendering.
There are some important implications to this because image data can be clipped during the conversion process which may happen unnoticed in the background. Issues arise especially if the working space is not large enough to contain all the image data which happens all to often.
Disappointment with image quality, especially in detail in dark, light or saturated areas may result and, although this may be thought an inevitable part of the process, there are sophisticated ways of controlling it. Taking control of this, by careful working space selection and properly managing the process, is something I provide training in. In an attempt to make a description of the ICC print profiling process easy to comprehend, many writers, myself included, have alluded to a process of comparison between printed results and the actual desired appearance of the patch file.
That's not entirely wrong in spirit, but, technically, calculating an ICC profile is NOT a process of comparison of printed output to patch values. This is because the patches actually have no "ideal" appearance i.
You read earlier that RGB and CMYK values are ambiguous, because the primaries are not defined, well, here in the printer profile, the ambiguous file values of the target are made unequivocal by the table calculating between printed output and target values. Color plays a crucial role in things we use and buy, and for those who design items like these for a living, ensuring color is accurately applied and displayed is a key aspect of their work.
With most of the steps in the design process now being executed digitally, designers are relying more heavily on their computers and monitors to guarantee the accurate display of colors.
In order to ensure the highest level of color accuracy, designers have to first familiarize themselves with a tiny set of data called ICC Profile, which plays a small yet decisive role in the design process. So what is ICC Profile? The profiles typically describe the color attributes of a particular device by defining the mapping between the device source and a profile connection space. Simply put, every device that displays color can be assigned a set of profile, and these profiles define the color gamut that will be displayed by these devices.
For most designers, the question then becomes, how do they make sure their monitors display the most accurate color? There are a few steps that they can take to smooth the process. Here is an example. These considerations led to the fundamental statement made earlier that the PCS for perceptual rendering intent represents desired appearance. The term "desired" implies that the PCS is oriented towards colors to be produced on an output medium.
Obviously, "desired" is open to various interpretations. However, in order to enable the decoupling of input and output transforms, it must be interpreted in a way that, to the greatest extent possible, transcends the capabilities and limitations of the specific color-reproduction processes, devices, and media for which profiles are to be provided.
For instance, an input profile for a slide scanner should attempt to yield "desired" colors, represented in the PCS, that are independent of the gamut and aesthetics of any specific output medium.
This independence, which decouples the PCS colors from the device colors, allows the input profile to be used in conjunction with any output profile. These desired colors will be based on the colors of the input slide but are not necessarily identical to those colors or limited to the gamut of the slide medium. They are the colors that would be desired on output if the characteristics of the potential output media could be transcended.
Similarly, the output profile for a color printer must reproduce the desired colors within the capabilities and limitations of the output medium and device.
This reproduction may involve some adjustment of the colors, as defined by the rendering intent, but it transcends the characteristics of any specific input medium and permits the use of the output profile in conjunction with a variety of different input profiles. With this PCS definition, it is the responsibility of the profile transforms to handle any required corrections or modifications to the colorimetry of a reproduction. Input profiles are responsible for modifying the colorimetry of the input media to account for adaptation, flare, and gamut limitations.
They also must provide the artistic intent implicit in the word "desired", which allows latitude for variation. For instance, the "desired" colors may be a close facsimile of the original, an aesthetic re-rendering of the original, or a simulation of a specific reproduction medium different from both the input and output media. Output profiles for media that are viewed in environments different from the reference are responsible for modifying the colorimetry to account for the differences in the observer's state of adaptation as well as any substantial differences in viewing flare present in these environments.
This is needed in order to preserve color appearance. Profiles must also incorporate adjustments to the dynamic range and color gamut of the image in order to accommodate the limitations of the actual medium.
One of the most fundamental corrections that must be applied to the measured colorimetry has to do with issues of tone reproduction and overall brightness level. These issues involve adaptive effects, as well as aesthetic and pragmatic considerations. When viewing a reflection print under normal viewing conditions i. A reflection print is perceived as an object in this environment in which the brightest areas in the image are those in which the paper or other substrate is blank no colorant.
Thus, the highlights must be considerably compressed in the reproduction. On the other hand, slides or movies projected in a darkened room do not suffer from the same limitation. In the absence of dominant external references, the observer's state of adaptation is controlled by the bright image on the screen. Thus, these media are designed to reproduce diffuse white at a lower luminance than the maximum attainable, which leaves some headroom for the reproduction of specular highlights and other very bright tones.
The same illusion is possible with back-lit transparencies and video, as long as the viewing environment is sufficiently dim that the observer is adapted primarily to the image, rather than the surround. The practical consequence of this difference is that the tonal compression of highlights is much less severe in the case of movies, slides, and video, than in the case of typical prints on paper.
All real media have a limit at the dark end of the tone scale, so that tonal compression is required in the shadows as well. Furthermore, the level of flare in the intended viewing environment has a strong effect on the apparent tone scale, particularly in the shadows and three-quarter tones; media designed for viewing conditions with different levels of flare tend to incorporate different amounts of flare compensation in their tone reproduction.
PCS colorimetry must also be corrected to account for the change in color appearance caused by differences in the absolute luminance level. For example, the lux illuminance of the reference viewing environment is similar to that of most actual home and office viewing environments but less than the lux often used in Graphic Arts and Photography. Corrections will typically be needed to correct for the brighter, more colorful appearance of reproductions when they are viewed at higher levels of illumination.
In photographic systems, the tone-reproduction characteristics are implemented in the construction of the sensitized layers and the chemistry of the emulsions and developers, or in the case of digital photography, in the image processing. In video, they are implemented in the electronics of the camera and receiver.
Thus, a color management system usually deals with an image originating from a medium or device that has already imposed its own tone characteristic on the luminances captured from a scene, so that the highlights and shadows are already compressed.
However, it is often necessary to reproduce the image on a different medium, for which the original compression may be less than ideal. In such cases, for best results, the tone scale of the image should be adjusted for the output medium.
The PCS and its reference medium provide a convenient interface for these tone-scale adjustments. Input transforms apply adjustments to map the tone scale of the original medium onto that of the reference; output transforms incorporate adjustments to map the tone scale of the reference medium onto that of the output medium.
These adjustments can take on many different forms, depending on the aesthetic effect to be achieved. In some cases, the appearance of the original may be accurately preserved; in others, it may be preferable to make deliberate alterations in the appearance, in order to optimize the rendering for the output medium or to simulate a third medium.
This range of possibilities is implicit in the phrase "desired color appearance" in the PCS definition for the perceptual intent. Output to media with a dynamic range different from that of the reference medium may be handled by tone-shaping techniques which compress or expand the tone scale to the range the device can handle. Furthermore, in output profiles, the different "rendering intents" can incorporate different adjustments. Some perceptual transforms, for example, can be designed to preserve the tone scale of the reference medium, clipping abruptly at the minimum reflectance if necessary, while other perceptual transforms may apply a more subtle reshaping of the highlight and shadow tones.
Input from media with a dynamic range different from the reference medium also may have tone-shaping techniques applied, along with luminance scaling to maintain brightness balance. These adjustments should be invertible in the sense that they match the precision of the data and the computation for high-quality output to the same devices.
For instance, images with an extended highlight range such as those from scanned photographic transparencies must be remapped for the reference medium, so that the highlights will be compressed to the range of the PCS.
The details of these techniques may vary with the intended market, the specified "rendering intent", and aesthetic choices made by the profile builder. If the intent is to preserve the appearance of the original, adjustments to the tone scale can be limited to those compensating for differences between the actual viewing conditions and those of the reference environment.
These include the effects of brightness adaptation, surround adaptation, and viewing flare. In other cases, there is plenty of latitude for profile vendors to differentiate their products with respect to aesthetic choices, while still basing their profile transforms on the common definition of the PCS.
Thus, proprietary art can be fostered and encouraged in a context of interoperability. Got a question about ICC Profiles or colour management? Information on profiles Finding profiles FAQs. Introduction to the ICC profile format 1. Background A large number of companies and individuals, from a variety of industries, participated in the development of the ICC specification which is designed to provide developers and other interested parties with a clear description of the profile format.
Device profiles provide color management systems with the information necessary to convert color data between native device color spaces and device independent color spaces. The specification divides color devices into three broad classifications: input devices, display devices and output devices.