Data is entered in boxes contained in the top row. Use the mouse to click in any of the boxes to make it the active box where data can be entered via the keyboard.
Type a gray %, for instance 2.5, in the first box. Click, then enter the L*, A*, and B* data in the appropriate boxes, then click "add point". The data will be added to the graph.
Only the Gray % and L* are required. You can leave A* and B* empty if you are only concerned with linearizing a step wedge measurement and won't be using the A* and B* data to make an ICC profile for soft proofing.
When entering data in a box it has already been entered, double click the mouse to highlight the entire number and type the new number.
This data entry widget was primarily designed to be used with the ColorMuse 2 colorimeter. However, it can also be used for entering step wedge measurements made with a densitometer. To activate this mode, click the tab at the bottom of the graph window that is labeled "Edit logD". This click will change the mode to densitometer data entry, and the gray % and logD reflectance can be entered in the appropriate boxes. Click "add point" to add this measurement.
This data entry widget allows you to edit any data point that has been entered with a mouse.
Data points that have been entered are a pleasing pink color. When you hover the mouse over this point, it turns blue. Holding down the mouse button on this point turns it a green color, and allows you to move it around - either to correct an entry error or just to smooth the curve. A readout of the gray % and the Y value (either L*, A*, B*, or logD density) will appear and allow you to finely position the point on the graph.
A pale blue line connects all the points, and indicates how any intermediate points between actual data will be written to any of the output file types.
Additional points can be added to the data by double-clicking the mouse at any point in the graph. That point will be added to the data and the spline curve adjusted accordingly.
Once all the data has been entered, pressing one of the three red buttons below the graph will resample the data shown in the graph to a standard 21-step data file. The 'save LAB datafile' will download a text file named Color-Muse-data.txt to your browsers' download folder. If you download more than one file of the same type during a session, most browsers will append some sort of number to serialize the name - e.g. Color-Muse-Data(2).txt for instance. It is probably a good idea to rename these measurement files something more memorable if you plan on using them in the future.
The middle download button will download a binary file that can be used inside Adobe Photoshop to linearize an image file. If a step wedge is printed from photoshop and the measurements have the typically compressed shadow and highlights, this correction curve will make the necessary alterations to the image in order for the tones to print in a linear fashion. This is the goal of all digital negative approaches, and will ensure that the image seen on the screen is faithfully reproduced by printing a specific process. The file is named PS-Curve.acv and will also download to your browser's Downloads folder.
This option creates a text file to use when building classic QuadToneRIP inking profiles. This so-called gray curve file has a specific format of pairs of input/output values that will be used to tell the inking profile how to make preliminary adjustments to input data to the .quad file being built. The format is a set of values inside a double-quoted string of the form "0.0;1.0 4.2;5.0 etc". Each of the input/output pairs are joined by a semicolon and pairs are separated by a space. With the availability of sophisticated QTR programs like Richard Boutwell's QuadToneProfiler family of products, this will probably not be that useful nowadays. The file is named QTR-gray-curve.txt and downloads just like the other options.
Below the file save options is a switch that can turn on the option to 'correct' the data being input to normalize the values to those created by the X-Rite i1-Pro series of spectrophotometers.
While both the ColorMuse 2 and the Heiland densitometer yield measurements that are very close to the i1-Pro, there is a slight drift in the values. The ColorMuse reads a little too dark at low L* values, and the Heiland densitometer reads a little too light at higher L* values.
I measured several known step tablets from Kodak and Stouffer's with all three instruments and decided to choose the readings from the i1-Pro as 'ground truth' and calculated a second order error-minimizing function to apply to the input values of the other two instruments that allow them to output essentially the same readings at any given gray percent.
These are very subtle changes, and leaving them turned off will not have any major effect on your results. If you are not using either the ColorMuse 2 or a Heiland reflection densitometer, you should leave this switch off!
Copyright ©2025 Clay Harmon
Permission is hereby granted, free of charge, to any person obtaining a copy of this software and associated documentation files (the "Software"), to deal in the Software without restriction, including without limitation the rights to use, copy, modify, merge, publish, distribute, sublicense, and/or sell copies of the Software, and to permit persons to whom the Software is furnished to do so, subject to the following conditions:
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This software uses the clean and elegant canvasSpliner Javascript graphing and spline-fitting library from Jonathan Lurie ©2017. It can be found on Github here. The library has been modified to support the additional needs of this software. This Javascript library is used and adapted under its existing MIT license.