How do icc profiles affect output

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.

It's vitally important at this stage that either the printer control software i. This method optimises the process. Thereafter, those same settings must be used whenever the profile is to be used.

Consistency is king, machine behaviour must be invariable. So, what are we printing in this patch file? The file data has no unequivocal appearance, the numbers are ambiguous. How can we see patches on screen then? We must not assign an ICC profile to patches in practice, because it could invalidate the printing process. So, it's not possible to send the data through the screen profile to the screen - therefore, to allow display, Photoshop assumes i. This doesn't affect the printing process, but it does explain why the file appears to have a set appearance on screen.

The printed patch set is measured using an accurate spectrophotometer. As you read above, after printing and reading the target no comparison to anticipated results is actually made, because there is no anticipated result for the printed patches. So, what does actually happen? Using the printer profile, printing. When selected in an imaging application like Photoshop, the printer's ICC profile provides a prediction, which is used, along with the document profile, to work out how to alter each of the document file's pixel values to get a print that looks like it should.

That is, it should closely match the source image shown on a calibrated and profiled display screen, or another print from a profiled workflow. As well as on-site profiling, I also offer remote inkjet profiling, here. Good printer profiles can be used in on-screen softproofing in order to predict printed output on a well set up monitor screen.

This useful output preview process is available in Photoshop and some other imaging applications; softproofing provides a screen preview, simulating the output of a printer, which can be viewed during image optimization.

Of course, accuracy in softproofing relies on having a decent quality, well calibrated and profiled, Display System and a good accurate output printer profile. Without going too deep, the process involves the original file's values passing "through" the printer profile en-route to the display profile.

The ICC input profile is used to compensate for consistent issues in the capture or scanning process. The relevant ICC profile is assigned to the image when opening any original capture or scan.

In many software applications, the profile can be assigned and embedded automatically. Assigning the ICC profile to an incoming image provides for accurate appearance on screen through a transformation using the input profile and display profile - and, often, also the chosen working colour space profile.

Unfortunately, however well intentioned they may be, ICC profiles supplied with products or found around the internet which might claim to accurately represent a particular device can often be quite poor. In some instances the provider even fails to provide instructions on device settings for use with their profile. Otherwise, use sRGB which is the default for most cameras. Advanced users may also consider using different profiles for different light sources.

For scanner profiles, some photographers create separate profiles for each type or brand of film scanned on a scanner. Output device profiles Describe the color space of output devices like desktop printers or a printing press. The output profile should also take into consideration specific printing conditions, such as the type of paper and ink. For example, glossy paper is capable of displaying a different range of colors than matte paper.

By assigning, or tagging, a document with a profile, the application provides a definition of actual color appearances in the document. But when tagged with the Adobe RGB color space, these numbers specify an actual color or wavelength of light—in this case, a specific color of purple. When color management is on, Adobe applications automatically assign new documents a profile based on Working Space options in the Color Settings dialog box.

Documents without assigned profiles are known as untagged and contain only raw color numbers. When working with untagged documents, Adobe applications use the current working space profile to display and edit colors.

Profiles describe the color spaces of the input device and the document B. Profiling software can both calibrate and characterize your monitor. Characterizing your monitor simply creates a profile that describes how the monitor is currently reproducing color. Brightness and contrast The overall level and range, respectively, of display intensity. These parameters work just as they do on a television. A monitor calibration utility helps you set an optimum brightness and contrast range for calibration.

Gamma The brightness of the midtone values. The values produced by a monitor from black to white are nonlinear—if you graph the values, they form a curve, not a straight line. Gamma defines the value of that curve halfway between black and white. Phosphors The substances that CRT monitors use to emit light. Different phosphors have different color characteristics. White point The color and intensity of the brightest white the monitor can reproduce. When you calibrate your monitor, you are adjusting it so it conforms to a known specification.

Once your monitor is calibrated, the profiling utility lets you save a color profile. The profile describes the color behavior of the monitor—what colors can or cannot be displayed on the monitor and how the numeric color values in an image must be converted so that colors are displayed accurately. Note : Monitor performance changes and declines over time; recalibrate and profile your monitor every month or so.

If you find it difficult or impossible to calibrate your monitor to a standard, it may be too old and faded.

Most profiling software automatically assigns the new profile as the default monitor profile. For instructions on how to manually assign the monitor profile, refer to the Help system for your operating system.

Color profiles are often installed when a device is added to your system. The accuracy of these profiles often called generic profiles or canned profiles varies from manufacturer to manufacturer. You can also obtain device profiles from your service provider, download profiles from the web, or create custom profiles using professional profiling equipment.

To embed a color profile in a document you created in Illustrator, InDesign, or Photoshop, you must save or export the document in a format that supports ICC profiles. You can embed a color profile in an object or an entire PDF. Acrobat attaches the appropriate profile, as specified in the Convert Colors dialog box, to the selected color space in the PDF. For more information, see the color conversion topics in Acrobat Help. There are very few situations that require you to change the color profile for a document.

These changes mostly removed ambiguities in the v2 specification so as to deliver a more precise definition of PCS.

The main benefit of using v4 is improved predictability of profile performance and reducing differences in interpretation. Regardless of which CMM is used, when a pair of profiles is used, they should always produce the same result.

The major improvements made in v4 over v2 are:. The dynamic range of PRM corresponds to high quality print. The ICC recommends using v4 profiles. However, there are still many v2 profiles out there, and some profile builders only make v2 profiles. ICC continues to support v2 profiles, and also provides information on how to make good v2 profiles.

Nevertheless, it is probably better to use v4 profiles to prevent ambiguity. An ICC profile is a file containing color information for devices conducting color communication. It was developed by the ICC, and two versions v2 and v4 are in use. ICC profiles are used in color management workflows to provide consistent color reproduction.

Also, these profiles contain data essential to accurate simulations on monitors, for example, simulating printing. This requires the use of a printer ICC profile. So the ICC profile is a very powerful tool for people working with color management.