Tone Curve Modes


Today’s Question: When I switch between the two presentations [parametric and point curve] for the Tone Curve in Lightroom at the bottom left is the title “Point Curve”. Should the title change to parametric when I am in the parametric mode or does it constantly stay as Point Curve? When I get the four sliders at the bottom, is that the parametric curve function or am I still in point control?

Tim’s Quick Answer: When you see the four sliders below the Tone Curve, you are in parametric mode. When you don’t see those sliders you are in point curve mode. These two options simply provide different ways to interact with the Tone Curve adjustment.

More Detail: The curve is always defined by points “behind the scenes”. In other words, the shape you’re defining is a series of Bezier curves, which require points to define the various changes in the shape of a curve. For example, an “S” curve can be defined by two points in addition to the end points. A simple arc could be defined with one extra point (in addition to the end points).

So, in a sense, you are always working with a “point curve”. And you always have the preset curve shapes available from the Point Curve popup regardless of which mode you’re currently working in.

The only difference between working in point curve versus parametric mode is how you interact with the curve. In point curve mode you are actually adding or moving anchor points directly on the curve. In parametric mode you are instead working with sliders (Highlights, Lights, Darks, and Shadows). Note, by the way, that you can still use the curve directly to adjust the slider values (by clicking and dragging directly on the curve), but you aren’t able to actually add or move anchor points directly in this mode. The sliders are simply intended to make it easier to manipulate the shape of the curve to achieve the desired effect in the photo.

Ultimately you are always refining the shape of the curve in order to change the appearance of the photo. The only question is how you are interacting with the curve. You can use the more simplified approach of using four sliders, or you can create and adjust multiple anchor points directly on the curve. The former is simpler, and the latter provides more control.