In short, all the Lightroom’s numeric sliders I could think of are linearly interpolated between the current image settings and the chosen preset, but only if the preset sets new values for that value. This way, you can apply e.g. sharpening preset and still keep your cross-processing look the same.

What is not applied:

• Point curve (maybe later)
• Graduated filters (maybe later)
• Red-eye removal
• Dust removal
• Adjustment brush
• Process version
• Color profile type
• Color/Black&White Mix toggle
• All attributes that select process or enable Auto-something, e.g. Defringe, vignette style, constrain crop, auto-exposure….

All values are interpolated linearly, except RAW white balance, which is (since v0.2) interpolated using 4 linear functions. This combination was figured out by dorfl68, the author of Paddy – thanks!

Outside 0-100% weight, it is still using the same linear interpolation, but as the value can go outside the proper range, clamping function kicks in. Without clamping, Camera RAW would just forget that the value is set at all.

After all the necessary values are interpolated, The Fader creates a “plugin develop preset”, which is then applied on the image. Every time a preset is applied, a new history entry will be visible on the image. Unfortunately, there is no way for me to prevent this, it’s part of the plugin API.

Here is the long list of Camera RAW internal develop settings which the plugin is using. If you notice anything missing, or values that have incorrect values, please get back to me!