In Exposure tab you can:
The exposure level is maintained when Calculate is set to ISO, Aperture, or Shutter and any of ISO, Aperture, or Shutter speed parameters is adjusted.
Invalid values are displayed in red. These values can’t be selected because exposure level would not be maintained — to maintain exposure level the calculated parameter would be out of the range of allowed values. For example when ISO is calculated and the minimum ISO value is 200, if selecting an aperture of f/4 would ajust ISO to 100 then f/4 is red and can’t be selected.
When Calculate is set to None all parameters can be adjusted freely.
Save Preset saves the current exposure for later retrieval. A category and name must be provided for the exposure. The Presets button displays the list of saved presets. Selecting a preset from the list initializes the current exposure with that preset.
Baseline saves the current exposure to the bottom of the screen as baseline for comparison with current exposure. Below the saved exposure the comparison between the current exposure and the saved one is displayed:
When Calculate is set to ISO, Aperture, or Shutter the exposure can be adjusted by selecting a difference (lighting ratio or ND filter) from Baseline.