I found what it was! I had added a Spot to enhance the face and  the side was lighter because of the angtle of the sun in the sky! Gosh I am sorry to have bothered the forum with such a stupid question! I need to examine before I post...... *blush I'll be more careful next time.
ThanX to each of you for your patience..
Ariana

Is there water in your future or is it being shipped away to be resold to you?
Water, the ultimate weapon...
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