ColorThink Pro - Grapher

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=The Grapher=
=The Grapher=
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<big>Color information can be ''complicated'' - and 2D and 3D graphs aid visualization and help in evaluating profiles, devices and printing processes. The Grapher will plot the ''gamut volume'' (or outline) of ICC device and Space profiles - and the color list from Named Color Profiles (NCP) in (Y)xy, (L)uv, or (L)ab coordinates. It will also plot ''color lists'' resulting from measurement data, synthetic test data and image file colors.</big> Device profiles include Scanner/Camera (“scan”), Monitor (“mntr”), and Printer (“pntr”) types. Device Link (“link”) and abstract (“abst”) profiles have no discernable gamut and therefore cannot be plotted.
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<big>Color information can be ''complicated'' - and 2D and 3D graphs aid visualization and help in evaluating profiles, devices and printing processes. The Grapher will plot the ''gamut volume'' (or outline) of ICC device and Space profiles - and the color list from Named Color Profiles (NCP) in (Y)xy, (L)uv, or (L)ab coordinates. It will also plot ''color lists'' resulting from measurement data, synthetic test data and image file colors.</big> Device profiles include Scanner/Camera (“scan”), Monitor (“mntr”), and Printer (“pntr”) types. Device Link (“link”) and abstract (“abst”) profiles have no discernable gamut and therefore cannot be plotted ''as volumes''. Their effects, however, can be graphed. For instance, an abstract profile can be applied to image / color data to create a vector graph.
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Revision as of 10:22, 17 September 2006

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Contents

The Grapher

Color information can be complicated - and 2D and 3D graphs aid visualization and help in evaluating profiles, devices and printing processes. The Grapher will plot the gamut volume (or outline) of ICC device and Space profiles - and the color list from Named Color Profiles (NCP) in (Y)xy, (L)uv, or (L)ab coordinates. It will also plot color lists resulting from measurement data, synthetic test data and image file colors. Device profiles include Scanner/Camera (“scan”), Monitor (“mntr”), and Printer (“pntr”) types. Device Link (“link”) and abstract (“abst”) profiles have no discernable gamut and therefore cannot be plotted as volumes. Their effects, however, can be graphed. For instance, an abstract profile can be applied to image / color data to create a vector graph.


Creating Graphs

Icon 2D.jpg Icon 3D2.jpg Click the 2D or 3D Grapher button on the Menu Bar to open an empty graph.

Controlling the Grapher - Zoom

The ColorThink Grapher was designed so manipulation of the plot item display was intuitive and powerful. The mouse plays an important role in this ability. A summary of its functions is:

Graph Elements

Graph Control Window

Example of the Graph Control window.
The graph control panel appears as a floating window in Windows and as a sheet attached to the Grapher window in Mac OS X. To show the graph control panel as a sheet, move the mouse pointer until it is just below the title bar of the Grapher window, centered near the “Grapher” window name. The sheet will slide out for you to make changes and then slide away when you move the point away from the control panel.

Dimensions

To select 2D or 3D: Click on the 2D or 3D radio button and ColorThink will change to that graphing mode.

example of a 2D graph
In each coordinate system, graphing in 2D removes the lightness component and the chromatic component is the only information plotted. As a result, the graphs show the outer edges of the gamut regardless of the lightness level of this information. For lightness information in addition to the chromatic information, use the Grapher in 3D mode.
3D graphs have the ability to display much more information than 2D graphs. Subtle gamut differences and color shifts are represented in 3D that are not possible in 2D. For example, in evaluating an inkjet printer which may be used for proofing purposes, it is important to determine that the inkjet can reach the same black point that the press or analog proof to be simulated is able to produce. In 3D it is immediately apparent when a proofer will not get dark enough whereas a 2D-gamut overlay would not reveal this information and the proofing printer might have mistakenly been deemed appropriate for the task.

Coordinates

To select the graphing dimension

Click on the Lab, Yxy, or Luv to change the graphing dimension:

The Yxy Chromaticy diagram is a popular 2D method for illustrating the gamut differences between different devices or printing methods. Yxy, however, is not perceptually uniform and so does not give an accurate illustration of gamut shape and size. For example, the greens in the Yxy diagram are exaggerated and plot covering a larger area than greens actually represent in our perception. For this reason Luv is included as a graphing coordinate system. Luv is designed to be more perceptually uniform than Yxy and the area devoted to each color more in line with our perception. The Lab coordinate system is also offered as a graphing option. Lab also offers a reasonable gamut shape and size representation but many claim also suffers from areas of perceptual non-uniformity.

In general we recommend the Yxy or Luv coordinates for 2D graphing only. Lab has been found to be easier to visualize, understand, and compare when creating 3D graphs.

Axes & Labels

Check the “Plot [vertical] axis” or “Plot [cross] axes options to plot lines for the axes. This can help with the visualization of color spaces

Spectrum Locus

Spectrum Locus
The Spectrum Locus is the curve defined by “pure” wavelengths of light plotted from 380nm to 730nm. The spectrum locus demarks the outer range of human perception – effectively the gamut of the human eye. The spectrum locus option is only available in the Luv and Yxy color spaces. Lab, by definition, is bounded by the human eye gamut. While Lab contains numbers that do not correspond to human-perceptible colors, the shape of the visible color gamut is difficult to determine and plot.

Background

Changing the Background slider will vary the brightness of the background.

Grid/Spin Tab

Example of the Grid/Spin tab

At the Grid/Spin tab, the grid lines can be turned on or off, including the foreground grid if desired. Turning off the grid can make it easier to see details in a profile, for example, without the grid obscuring the field of view. Capturing and compressing pictures and videos can often be done with a smaller file size when the grid is turned off.

Spin Control

The spinning of the plot items in the graph can be controlled several ways:

The Slicer

Example of the slicer controls tab
Graph window with slicer turned on.

With the slicer turned on, a luminosity slider opens up on the graphing window, and a horizontal plane is "sliced" through the plot area. This allows the viewing of a profile, color list or image pixels at various sections of the color gamut. For example, individual pixels in an image can be compared to the gamut of the printer to be used.


Plot Item Control

Example of Plot Items window

To Add plot Items

To Remove plot Items

To Show or Hide Plot Item

Check or uncheck the box to the left of the plot item in the Plot Item Listbox.

Checking the box will also select the plot item. Unchecking a box will not select the plot item.

To Highlight a profile (2D only)


Setting Plot Item Colors

  1. Select an item in the plot list,
  2. Select:
  • True Colors All color points and vertices are colored using the actual Lab color values processed through the current monitor profile. Colors outside the gamut of the monitor will be plotted as the closest possible color (using the relative colorimetric rendering intent and the current CMM)
  • Single Colors All colors in the plot item will be colored using a single color. The next available single color will be selected for the plot item. To change the plot color, select a different color from the adjacent popup menu.
  • Delta-E Coloring (available in Vector mode only). Delta-E coloring will color the vectors (color shifts) in a plot item using green/yellow/orange/red depending on the amount of color shift depicted by the vector. To change the criteria for the error levels at which the color changes occur, select the “Delta-E Colors” tab and move the sliders in the color bar. In this manner you can select your shop-standard error levels and evaluate color shifts according to your own standards.

Tone using L*

Tone using L* - For true-color accuracy ColorThink darkens the colors plotted according to the Lightness (L* component of Lab) value of the color. This can cause dark colors to become invisible against dark backgrounds. Uncheck this box to remove the darkening effect and lighten the dark portion of the plot item. The colors are less accurate but details in shadow colors are much more visible.

Opacity

To vary the Opacity (transparency) of a plot item:

  1. Select the plot item in the list.
  2. Drag the Opacity slider left or right to decrease or increase the opacity of the plot item.

This is especially helpful for turning a profile gamut volume transparent so color data or other profile gamuts located inside or behind the current profile are visible. Please refer to the Tutorials section for an example of this technique.

Working with Points

Example of the "Plot as Points" option

Primary and secondary colors.
Neutral gray plot
  • - The points on the surface of the gamut,
  • - Only the primary colors (Red, Green and Blue) within the profile
  • - Only the primary and secondary colors (Red, Green, Blue, Cyan, Magenta & Yellow) within the profile
  • - The RGB Device Neutral colors (grays).

Working with Vectors

Plotting colors as vectors allows a graphical view of color shifts in 2 or 3 dimensions. This is a powerful technique to quickly get a feeling for how color shifts are occurring in different colors (different areas of the 3D color space) and what types of shifts (lightening/darkening, hue shifts, saturation changes) are occurring.

Vectors can be used to:

- Color shifts as inks dry
- Differences between papers
- Differences between ink sets
- Differences between printers

The vectors will look like little tadpoles. The dot will appear at the end of the vector and represent the color that is second in the list of plot items. Think of it as the first list is the "before" and the second list the "after".

This feature can be very useful for viewing device drifts, how different printer/ink/media settings affect color, or how different filters on your reading device affect the color values.

Enabling Vectors

  1. Select an Image or Color List plot item and click the “Vectors” button.
  2. A “destination” box will appear.
  3. Drag your comparison data or a profile into the destination box.

Comparison data can be another color list or image file. It is suggested the original color list and the “destination” color list have the same number of colors. If the number of colors in each list differs, ColorThink will plot all the vectors for which a color exists in each list. Additional colors in the longer list will be ignored.

If you drag a profile into the “destination” box, ColorThink will “round trip” the color list and show the color shift that occurs as a result of this conversion. This round trip consists of a conversion from Lab to the color space of the device profile and then a conversion back to Lab using the same profile. Assuming the “back” or “proofing” conversion of the profile is accurate, this round trip transform will show how much color sift occurs as a result of the profile application. You will see out-of-gamut colors shift in-gamut to as to become printable, in-gamut colors shift due to perceptual renderings or profile errors.

Rendering Intent (profiles only)

To change the rendering intent used for the conversion (the Lab->device part of the conversion):

Coloring by delta-E - see delta-E color in Plot Item Control above.

Working with Volumes

When plotting profiles, ColorThink shows the device gamut captured by the profile using a gamut volume shape (for 3D graphs) or a gamut outline (for 2D graphs). The appearance of that volume can be in three different styles:

  1. Wireframe is the simplest plot and joins the vertex points together using lines. Linearity/calibration of the profiled device shows as differing spaces between the lines.
  2. Flat Each 4-sided polygon on the gamut surface is rendered using a single, solid color. This effectively shows the gamut volume, the linearity/calibration of the device and the color representation of the locations in the Lab colorspace.
  3. Smooth Each polygon’s color is rendered smoothly, blending the different corner colors across the surface of the polygon. This is the most accurate color rendering of the surface of the device gamut but at the expense of gamut surface detail.

Resolution

Some profiles might have fluctuations along the gamut boundary. In these cases a higher resolution can be selected to provide more precise gamut calculations. Be aware, however, that the smaller the resolution, the longer amount of time it will take to create the gamut plot.

To change profile volume resolution:
At the "Res" drop-down box...

&&& Rendering

Device Gamut

Other intents

Constrain Channels

Tutorials & Guide Tests

See the tutorial section for an example of how to use these different styles along with varying gamut volume opacity to clearly compare and contrast two device gamuts.


Working with Profiles

&&&

as volume

as points

Working with Images & Lists

as points

as vectors

Saving Graph images

Windows
Mac

ColorThink Pro can save the graph window as an image in either "BMP" format (Windows version) or "PICT" format (Mac version).

1] Go to File, Save as BMP image (Windows) or Save as PICT image (Mac)

2] Choose a file name for the image and the location at which you wish to store it.

Quicktime Video

Saving Graph as QuickTime Video file

You can also save the action in the graph window in motion in a QuickTime video. This allows the sharing of 3D graphing with anyone who has a QuickTime viewer.

CTP movie1.jpg
CTP movie2.jpg

1] Go to File, Save as Quicktime Video

2] Choose the frame rate.

3] If "Specify Quicktime Options" is checked, you will be given options for compression format and quality in the next step.

4] If the slicer has been turned on in the Grapher, the "animate slicer" option is activated when saving a QuickTime movie.

5] The Compession Settings dialog box comes up if "Specify QuickTime Options" has been checked in #3] above. This allows the user to specify what compression type to use, how many frames per second to be captured, and the quality of the compression of the video. In most cases, the larger the number, the larger will be the file. It is possible to reduce the file size by adjusting the display of the grapher. Most compression algorithms will be more efficient with simpler graphs, so turn off the grid and simplify the background to reduce the file size of the movie.

There is a very large selection of available compression types to choose from. We find that Photo - Jpeg works well and provides a good quality image.

&&&

Keyboard Shortcuts

While in the Grapher...
To Save a Graph

Press control/command-S to save an image file of the graph window.

To Save a QuickTime movie

Press shift-control/command-S to save a Quicktime movie of the graph window.


Go on to Chapter 7 - "The Worksheet"

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