The red, green and blue fields of the currently loaded image can be pushed to the stack using the first line of the "Colour space conversion" section of the tool. Select the fields you wish to push to the stack in the RGB check list, and then press the "RGB push" button. The images will be pushed in reverse order, so that for example if all three buttons on the check list are selected, the red field will end up on top of the stack, the green field will be second on the stack, and the blue field third. The images will then be available for manipulation in the Imcalc tool, or display in the Imcalc Tv's.
The process can be reversed using the "R Pop", "G Pop" and "B pop" buttons. Pressing these will take the top image from the Imcalc stack and load it into memory as the currently stored red, green or blue field. If one of the other fields has already been loaded (either by loading a colour image or by popping and image from the stack) then the size of the new field must be the same as that of the others already loaded.