In the false color image, "Black" corresponds pixels with a small number of counts and "White" to pixels with a large number of counts, with a range of hues in between. You can change the maximum and minimum values (white and black) by dragging the two sliders to the right or left, or by entering in the desired values in the boxes to the left of the sliders.
Buttons just below the slider allows you to change the nature of the color scale. If set to Linear (default), the color scale is linear with the counts/pixel from the smallest to the largest. If it is changed to Logarithmic, the color is proportional to the logarithm of the intensity.
The "Color Scheme" drop-down menu allows you to specify the rainbow of colors on going from black to white--more red, more green, etc. Each choice corresponds to a different color. The last two options are black-and-white only, which may be useful if the image will ultimately output to a black/white printer. "White/Black" produces an image similar to the previous ones, with whiter pixels corresponding to more intensity. "Black/White" produces an inverted image, with blacker pixels corresponding to more intensity-this one looks very much like old- fashioned photographic film.
The Contour button provides an alternate way of displaying the data, replacing the false color display controlled by the color scale and color scheme. Constant intensity contours are drawn at selected intensity levels. The resulting image can be zoomed or written to a file in the normal way.
Clicking on the Contour button switches from Linear or Logarithmic mode to contour mode. The default is a set of logarithmically spaced contour lines. The number of contours, intensity value for each contour, and color of each contour line can be altered in a new window that is opened using the Levels button. The contours will be immediately redrawn if you click the Apply button, assuming that you have already clicked the Contour button--otherwise, the changes will take effect the next time you go into contour mode. If you decide to play with the contour levels and/or colors, keep the following in mind:
  • The program assumes that the intensity levels are in increasing order. Arranging them any other way may lead to unpredictable results.
  • The time to draw the image is approximately proportional to the number of contour lines chosen. You will see a real decrease in performance if you select too many contour lines.
  • Too many contour lines can also make an image too busy.
  • Adjacent contour lines should have very different colors, otherwise you will not be able to figure out where the changes happen.
  • You cannot change the parameters of a contour line whose index is greater than the maximum number of lines to be drawn.
  • The ultimate information of the data is limited by the pixelation. Things may look a little odd at extreme magnification.
  • Low-statistics data will result in very noisy, fractal-looking contour lines, because the contour lines faithfully follow the contours of the data including statistical fluctuations. If you are looking at broad features (which is typically the case if you are using contours at all) consider using the Condense option to bin together pixels, resulting in better statistics but poorer resolution.