Just when I thought I was getting a handle on understanding characteristic curves, I came across this one (scroll down to the second page): http://bergger.com/media/wysiwyg/Fiches_techniques/BERGGER_PANCRO_400_DATASHEET_01_2017.pdf Here are my questions. First, I understand the vertical axis - that is simply what the densitometer sees, but what about the horizontal? It is labelled "relative log exposure" but is in whole numbers, rather than stops (i.e., 0.3, 0.6, etc.). Second, what does this curve tell us? The toe looks a little odd, starting so high. Any light you can shed is most appreciated. Try to keep it really simple. I have great difficulty with these sorts of things.