This is, okay. So, look at these pictures. This one, then you apparently for you to see the rich colors. Then you are using your cone photoreceptor. Also, look at this picture, so no much colors. What kind of photoreceptors you are using? Okay, it's quite tricky. So, the cone photoreceptor of course can give you a color vision. And this one with color but it's still you are using your cone for the receptor. You don't see the colors because the picture yourself with no colors. You still using your cone photoreceptor, because this is the bright light vision. Under these conditions, your photoreceptors are not working. It's saturated, okay? [FOREIGN] Like a rod photoreceptor. [FOREIGN] It's not it's the same meaning as we talk about the evening right now because you have the artificial lighting, right? So, when you can see the colors that kind of light illumination those conditions you are not using your rod photoreceptor, okay? [FOREIGN] You cannot see any colors array, it's just black. And then gradually you can see, maybe some kind of images happens. Maybe your friend sees some whale. You just see the ships there but you cannot recognize the colors of their clothing, right? So, in those conditions, you are using rod photoreceptor. And then maybe under some conditions you will use, it's like a light illumination. It's a bit brighter but not enough to saturate the rod photoreceptor. Then you both [FOREIGN] reporting to your brain, okay? So, this one, of course, it depends on our color photoreceptor. This is color vision. For color vision, actually, we need to go to this gentleman, Newton. He did quite famous experiments, actually, in those days. The first one actually is this one. If you just use a prism and then you can split the light in two and deepen the colors, right? This is the [FOREIGN]. And then of course you can isolate this single color [FOREIGN] but interestingly, if you give two lights. Let's say this green and the red together shine on the same spot. What happened? You will see a yellow here. If you compare this yellow and this yellow, they're completely different. I mean, maybe for you the perception they're the same. Both are yellow but then the physical property of these two yellow lights, are completely different. This is actually the single wavelength here. Not single. It's just a more pure band of the yellow light. But this one, actually is two. LIke a combination of the red and the green, okay? Then that tells you something already. If you think hard. Indeed, in those old days. Like a, [FOREIGN] that is actually how we can see color, yep? The color, as we said here. These two yellow are so different, the physical properties. But for us, they're actually the same perception. So, this actually- These two gentlemen we should talk about Thomas Young and Helmholtz. These two actually really great thinker, actually in those days, actually, didn't know any anatomy or electrophysiology, and they tried to think about how we can really make the color vision. See color. And then the purpose that you see this is the theory, actually, called [FOREIGN] 1802. This gentleman proposed [FOREIGN]. So, we only have three kind of basic type of photoreceptors in the eye, okay? And each of the three types of photoreceptors sensitive to particular range of visible light. Each cell's actually responsible for different light sensing. And then in 1850 Helmholtz then developed this theory further. [FOREIGN], so [FOREIGN] just three types of cone photoreceptors, blue and green, and red, [FOREIGN]. And then the relative strength of these signals detailed by the three types of cones are interpreted by the brain as a readable color. [FOREIGN] the brain. [FOREIGN] of course, at those days, actually, no any other evidence. This is just actually, by this kind of experiments actually, they really kind of have great insight. [FOREIGN]
