vdis10021 working in digital design - lecture 4 - digital colour management

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This lecture is an overview that defines what digital colour is and how it can be managed through appropriate workflow to result in consistent colour outcomes for either web or print.

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  • Lecturer: Rachel Hawkins VIRTU DESIGN INSTITUTE WORKING IN DIGITAL DESIGN VDIS10021 DIGITAL COLOUR MANAGEMENT
  • VIRTU DESIGN INSTITUTE: WORKING IN DIGITAL DESIGN - VDIS10021 2 What is Digital Colour Digital Colour is usually referred to as a Colour Space, Colour Model or Colour System. A Colour space is an abstract mathematical model which simply describes the range of colors as tuples (a data structure consisting of multiple parts) of numbers, typically as 3 or 4 values or colour components (e.g. RGB, CMYK, LAB). Simply speaking, colour space is an elaboration of the coordinate system. The majority of monitors adopt RGB color space because it is a convenient color model for computer graphics and the human visual system works in a similar way. This includes monitors on computors, smart phones, cameras and other similar devices. The most popular RGB color spaces are sRGB and Adobe RGB. An RGB monitor synthesizes colors additively by selectively illuminating each of its pixels red, green, and blue phosphor dots at varying levels of intensity. The light from a pixels three phosphor dots blends together to synthesize a single colour. In additive colour synthesis, all hues of the visible spectrum of light are mixtures of various proportions of one, two, or three of the primary colours of light. COLOUR SPACE Available colour systems are dependent on the medium with which a designer is working. When painting, an artist has a variety of paints to choose from, and mixed colours are achieved through the subtractive colour method. When a designer is utilizing the computer to generate digital media, colours are achieved with the additive colour method. Subtractive Colour - When we mix colours using paint, or through the printing process, we are using the subtractive colour method. Subtractive colour mixing means that one begins with white and ends with black; as one adds colour, the result gets darker and tends to black. CMYK is a subtractive colour system. The CMYK colour system is the colour system used for printing. ( Cyan, Magenta, Yellow, Black) Additive Colour - If we are working on a computer, the colours we see on the screen are created with light using the additive colour method. Additive colour mixing begins with black and ends with white; as more colour is added, the result is lighter and turns to white. RGB is an additive colour system. The RGB colours are light primaries and colours are created with light. Percentages of red, green, http://en.wikipedia.org/wiki/Color_space http://www.worqx.com/colour/color_systems.htm
  • VIRTU DESIGN INSTITUTE: WORKING IN DIGITAL DESIGN - VDIS10021 3 Conversion/Colour translation Colour space conversion is the translation of the representation of a colour from one basis to another. This typically occurs in the context of converting an image that is represented in one colour space to another colour space, the goal being to make the translated image look as similar as possible to the original. Working With Systems The Visible spectrum consists of billions of colours, a monitor can display millions, a high quality printer is only capable of producing thousands, and older computer systems may be limited to 216 cross-platform colours. Reproducing colour can be problematic with regard to printed, digital media, because what we see is not what is possible to get. Although a monitor may be able to display true colour (16,000,000 colours), millions of these colours are outside of the spectrum available to printers. Since digital designs are generated using the RGB colour system, colours used in those designs must be part of the CMYK spectrum or they will not be reproduced with proper colour rendering. Working within the CMYK colour system, or choosing colours from Pantone palettes insures proper colour rendering. Indexed colour Indexed colour is a technique to manage digital images colours in a limited fashion, in order to save computer memory and file storage, while speeding up display refresh and file transfers. It is a form of vector quantization compression. This images is a 256 colours. CIELAB and CIE XYZ CIELAB and CIE XYZ are similar colour models designed to approximate human vision. Because these colour models include so many colours, they are both used when translating from one colour model, such as RGB, to another, such as CMYK. These are referred to as profile connection spaces (PCS). For instance, Photoshop uses CIELAB as a reference colour space when it converts from one RGB profile to another RGB colour space. Photoshop uses CIE XYZ when it converts from the RGB colour mode to the CMYK colour mode. Its possible to use the CIELAB colour space for image editing in Photoshop, although few choose it for that purpose since it is not as easy to understand as the other colour models. http://en.wikipedia.org/wiki/Color_space http://www.worqx.com/colour/color_systems.htm L*a*b* colour uses three channels to represent the theoretical range of human vision: Lightness (L*), and two colour channels of opposing values of red-green (a*) and yellow-blue (b*). L*a*b* colour is different to RGB and CMYK in that it is both a colour model and a colour space. It is also a device- independent colour space, meaning that its colour values are absolute and not tied to any particular piece of hardware. http://dpbestflow.org/colour/color-space-and-color-profiles
  • VIRTU DESIGN INSTITUTE: WORKING IN DIGITAL DESIGN - VDIS10021 4 What is Colour Management? Colour Management is the process of tuning your cameras, scanners, computers, monitors, software and printers into a universal standard for colour so that you can ensure accuracy when reproducing images. Color management is not about making photos look better or getting the best color out of a particular device. Color management aligns an entire system of cameras, displays and printers so that the different color spaces (colors) produced are as close as possible. For example, factors such as the color of printing paper, the lighting in the room and lighting in the original photo can all affect the way colors appear. Color Management is a way to set up your environment and process (called a workflow) to allow all these devices to speak the same language so you can get accurate and predictable results. The ultimate goal is to match the colors of the image displayed on your monitor with the ones produced by your printer. Why colour manage? Good colour management will improve the accuracy of colour reproduction between digital input, monitor and digital output. Monitors and printers all have their own colour idiosyncrasies and it is impossible to make them a perfect match. It is however possible to convert the color data of each device via a common color space so that the various colours can match more closely. This is the basic principle of color management. The fact is all your devices scanners, digital cameras, monitors, and printers reproduce colors differently. There are even differences in the way individual printers of the same model manage color. Many variables affect color, including your ink and paper type. What is involved in colour management? Using special hardware and software you can program your digital devices to perform to standards that you determine. This process is the creation of Profiles. The resulting profiles are then slotted into your studios workflow. Once you have installed a profile you can then determine the devices performance based on that profile. Color management can be performed by following a set of rules to correctly handle the data. Color management will not only improve the end quality but also bring other major benefits to each work step. In addition to colour profiles you need to calibrate your devices so the colour display is as consistent as possible across all of them. http://suitecreative.com/studio-services/colour-management/
  • VIRTU DESIGN INSTITUTE: WORKING IN DIGITAL DESIGN - VDIS10021 5 Simply, color management provides a unified environment for handling colors where a common color reference is used at each step of production, from photography to design, plate making, and printing. From the Eizo Color Management Handbook
  • VIRTU DESIGN INSTITUTE: WORKING IN DIGITAL DESIGN - VDIS10021 6 Colour management fundamentals Putting in place a good colour workflow ensures the best possible results for your digital images. Colour workflow is required regardless of if the images will end up in print or on the web. Consistent and accurate results save both time and money for you and your clients. There are three fundermental stages in colour management: If we focus in on each of these areas there are several steps that can be taken to ensure the workflow addresses all colour influences in the journey between input and output. Step 1: Light Sources - The colour of an image at the capture stage is heavily influenced by the environmental light sources like the sun, light bulbs or a camera flash. Being aware of these influences and controlling them will improve colour results for input. Step 2: Input - Capturing and image through a camera or scanner can be influenced by the type of lens and scanner type. Creating a device specific colour profile will mean that you can predict what colour will be captured by the device. Step 3: Profiling - Most digital devices have dependent colour systems. This means that each devices colour differs depending on the settings of that device. It is therefore important to profile each device and install the profiles to result in device independent colour with consistency across the board. Step 4: Process - Once your monitor has