What causes "Shadow Compression" tool to be turned off?

I’m using Rawtherapee 5.4 on Windows 7. I’ve done some editing using a few different tools. Now I find that the “Shadow Compression” slider on the Exposure tab has been turned off. I presume this has to do with something I’ve done but have no idea what that might be. I also suspect that there may be multiple ways to cause such an effect. Documentation for this tool in Rawpedia is pretty sparse.

I’d be grateful if someone could either explain or refer me to something that does?

Shadow compression is off when the Black slider is on 0. They are linked together and there is no compression possible when there is no adjustment to the blacks :slight_smile:

Thank you! It now looks like I must confess to wrongly characterizing Rawpedia. I was mistakenly looking at “Shadows/Highlights” page whereas what you say is pretty clearly stated on the “Exposure” page.