That almost ends our lesson on frequency. There's just one more thing that I wanted to talk to you about today, because it's so prevalent in the processing that you're going to be doing. Some psycho physicists, Campbell and Robson studied a long time ago the contrast sensitivity of the human eye, human vision system not just the eye. Now what you're looking at here is a curve where frequency goes up to the right and contrast goes up down. And probably, if you're like me, hopefully you're not like me, one of me is way more than enough, as my children will tell you. But anyway, if you're like most humans, you probably can see this stuff really well, but not so much up there. And somewhere around there, that curve is where the fall off is. That essentially, you know, lower contrast up here, you can't really see the variations. Same thing with this high contrast, okay? Your eye is sensitive in different ways. So what this means is that some frequencies matter more in terms of the importance to you in an image, okay. In particular, if I were to leave out a bunch of that freq, you know, frequencies. So that is, if there was low contrast at the high frequency, you wouldn't even know, so you can use that to do image compression.