[vtkusers] ColorLevel Operation?

[Glenn Pierce]

Hi 

I am having trouble understanding the ColorWindow and ColorLevel
properties of mappers.

I have read lecture 5 on vtk located at
http://noodle.med.yale.edu/~papad/seminar/lecture5.ppt

and that shows the graph of input intensity against output intensity.
This also show the how the values of color level and colorwindow fit
into the picture.

However, I have a program where I can change the ColorLevel and
ColorWindow interactively. When I lower the color level the image
becomes brighter?
>From looking at the graph in lecture 5, shouldn't lowering the colour
level reduce the output intensity and so make the image darker ?

I have attached two images that show this.

If this is not how the colour window and level work is there somewhere
that describes these two functions in detail ?

Thanks very much for the help.

Glenn
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