As the transition point moves more left, the darker points of the image become more and more washed out. While some of this is desirable, we need to be able to control the effect a little more precisely. For this exercise, set the transition point at about 23, and add a new control arrow at about 13. This placement has the effect of anchoring the curve and allows us to control the stretching of the darkest shadows. Like the transition points, the placement of the anchor point(s) needs fine tuning.
Anchor points can also be used within the Sabattier effect area to control the effect, as well as in other places to limit unwanted ide effects of the transform. Do the basic manipulation first, concentrating on the transition points, then add and adjust anchors to control the effect within the transition points.
Some other points to be noted with this transition point setting