I have CS3 on one computer and CS 5 on another. On CS3 my dynamic brush options have a section called ‘Other Dynamics’ that allows me to change jitter opacity, but my CS5 does not have that option in the same area.
Does CS5 not have ‘Other Dynamics’ for brushes or is it just somewhere else?
Go to the Brush panel (Window -> Brush, or F5), select the “Brush” tab. You will find “Opacity Jitter” in the “Transfer” section.