How to Use the PXLab Vision Demonstrations

Starting the applet version of the program will give you the following initial frame.

The menu entry Select allows you to select an demonstration. Demonstrations are grouped into more or less meaningful subtopics which have their own submenu. Selecting an item shows you the respective demonstration.

Every demonstration has three parameter panels: Color, Geometry, and Timing. The color panel shows the current object's color coordinates in one of several possible color systems. The default system shows the CIE xy-chromaticity plane and a luminance scale. Also shown are numerical coordinates and test patches of all color parameters. Pressing a color system button changes the current color system display. Color charts show a light area which contains those chromaticity values which can be shown on the current color device at the currently selected luminance level. Changing the luminance may result in a change of the valid chromaticity area.

Here is the same image using the CIELab color chart.

The geometry panel shows the geometry parameters of the current display. There are several types of geometry parameters. Changing a parameter is immediately reflected in the demonstration image.

The timing panel shows a display object's timing parameters. These are mainly used for the design of experiments are not explained here.

The main menu entry Options controls which numerical coordinate fields are visible, how colors are handled which can not be shown on the current device and what is shown in the color chart.

Moving the mouse pointer on a color field in the color panel or pointing at a display element in the demonstration panel selects an element of the display as the currently active element whose color is shown in the color chart. Pressing the right mouse button in the demonstration panel opens a pop up menu. This menu contains entries for saving the current image to a file, copying the current color to the system clipboard or to the color panel's color board, and some other entries.

Demonstrations which contain animated images or movies have the Animate button activated. Pressing this button deactivates all other buttons and starts the animation.

There are demonstrations which contain subgroups (called "timing groups" in PXLab) of elements which may be shown separately. Here is a simple example:

This display contains two subgroups which is indicated by the buttons labeled "x", "1", and "2" below the main menu. Pressing "x" shows all subgroups together. Pressing "1" shows subgroup 1 which contains the background, the big square and the small square. Pressing "2" shows subgroup 2 which contains only the the center square. Note that the subgroups are not exclusive but every single display element may belong to more than one group. These groups are used by PXLab for high precision timing in experiments. So here is what we get if button "2" is pressed in order to present only group 2.

Some demonstrations ("Spectral Colors") do not define colors from 3-dimensional coordinates but simulate lights and surface reflectances. Here is an example for two metameric gray patches which are partly covered by a transparent slide:

These demonstrations open up an additional frame which contains all spectral distributions involved and also allow interactive manipulations of the spectra.

The left side contains the independent spectra. The first is the simulated light source (CIE standard light source "C") behind the whole display. This panel has a spectral distribution and an intesity scale. The second panel on the left ("N 5/") contains the transmittance function of the background white. Then we have the two metameric gray transmittance functions ("MG1", "MG2") which make up the small central patches and the last panel on the left contains the filter transmittance ("5R 7/4") which actually is the remittance of an entry in the Munsell Book of Colors. The right column of the spectral distribution panel contains the spectral output distributions of the respective areas.

© H. Irtel, 2006.