Lightroom’s Develop module has 7 groups of adjustment tools:
- Tone Curve,
- HSL / Color / Grayscale,
- Split Toning,
- Lens Corrections, and
- Camera Calibration.
These groups appear in the image below, and on all but the first group there is what appears to be a little switch, as highlighted below:
These widgets are, in fact, switches. “Flicking” a switch off and does just what you think it would: it turns the group’s effects on or off. And, by enabling & disabling a group’s effects, you can…
- easily discern the effects that group’s tools have on your image, and
- temporarily disable the tools within while still keeping their values for possible future corrections.
And since the switches behave independently, flicking one switch won’t affect the tools in another group; this behaviour allows you to keep all of your other adjustments in play (ie: turning the Tone Curve switch on and off has no bearing on the Split Toning adjustments).
So why bother tinkering with them—why not stick to scrubbing through the image’s adjustment history or dig into the stack of undos & redos that pile up during the touch–up process? Think of the switches as having a different access point to the adjustments applied to your photos: undo/redo and the history require you to move through your edits in a sequential fashion, whereas the switches allow you to selectively move in and out of your edits at your leisure. And on a somewhat–related note, it should be noted that toggling a switch is added to the undo/redo stack but it is not recorded in the history.
Now, as to why the “Basic” adjustment group doesn’t have a switch is beyond me… any ideas?