Clarification the Save Modes from IR and Caustics

[S_K_I]

I'm a bit confused in regards to the save function with Caustics which the documentation doesn't clarify. Will I need to compute an entirely new caustics map if I change the resolution of render? What kind of impact will it have if I computed the caustics at 1600x1600 and then re-rendered at 3200x3200 but using the previous generated caustics file? What other settings if I modify will require me to re-render the caustics map excluding what is on caustics options of course?

Additionally, if I set the mode to From File it greys out the option Auto save and Switch to saved map become greyed out, I don't understand why it does that. Can I get more simplified explanation what that indicates?

Thanks.

[Svetlozar Draganov]

Caustics map is not resolution dependent so you can use the same caustics map with any resolution without any impacts.
Please note that maps that look OK on small resolution might need more photons on higher ones, this however is not because the map is generated on smaller resolution but because the higher resolutions may requires more details.

Caustic recalculation is only needed if caustics subdivisions or photon emit radius(for the sun) have been changed, the parameters in the Caustics tab in render settings does not require re-calculation since they are applied once the map is calculated not during its calculation.

Auto save and respectively Switch to saved map options are available only when the Mode is set to New Map.
What those options do is to save and load the map automatically once generated.
When Mode is set to From File and you load the map manually there is no need to re-save it re-load it that's why those option are disabled(greyed out).