LAWRENCE MAYHEAD wrote:

Hello again Alberto,
Many thanks for your reply to my mail. The problem is that if I move the
slider away from the start position either way left or right the contrast
changes as expected BUT when I return the slider to exactly the same place
the contrast is different! in fact I cannot return to the original with any
setting of the slider!   [snip]

Hi Laurie and John,

   problem verified and already fixed now.
Now that you have specified that returning the slider at the start position
didn't restore the exact contrast as it were there, I specifically checked
for this, and, sure enough, it happened on my PC too..
The fix has been trivial, just make the initial value of a variable congruent
with the initial position of the slider. It was in the beginning, but then I 
changed
one without changing the other...
TNX you both for your report, and check the Web site for the new version
in a couple of days.

73
Alberto    I2PHD