How to undo Image->Adjust or Process

After performing Adjust->Threshold or Process->Sharpen, I cannot seem to undo it with
Edit->Undo or ^Z what’s the right way to do it?

Those options should work to undo one step only. ImageJ/Fiji does not provide a way to undo many steps, so you should try to keep always a copy of your original image.


@Peverall_Dubois, if your image has been saved previously you can do File > Revert to recover the last saved version.

One way to keep your original image as @iarganda suggested is to run Image > Duplicate (cmd-shift-D on Mac) before trying out a command.