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! It is strange and may be my computer,although I did
reload the progran just to be sure and the effect is still there. If no one
else has this problem please ignore it and I will try to sort it out here, I
dont want you to hold things up for what may be a mistake of mine.Many
thanks Laurie.