Of course, rods are hugely more sensitive, which is why we see in B&W when the light is dim. (And while a single rod can respond to a single photon, in practice it takes 5-10 photons to create a response in the visual cortex, and given the fact that most photons entering the eye fail to hit a rod, we end up with an actual quantum efficiency of just 1-5%.)neufer wrote:While it is true that we have many more orange sensitive L cones & green sensitive M cones than blue sensitive S conesChris Peterson wrote: Our eyes are least sensitive to blue light. Our short wavelength cone response is one to two orders of magnitude less sensitive than our long wavelength cone response.
Another factor to consider is that the cone density of short wavelength cells is also lowest. Our blue sensitivity isn't just poor, so is our blue resolution. This is very easily seen if you're out at night and observe a commercial sign with illuminated blue letters against a dark background. The writing will look out of focus. But it's not a focus problem; the failure is happening in the retina itself.
...we have about 15 times as many green-blue sensitive rod cells as all our own cone cells.
- A rod cell is sensitive enough to respond to a single photon of light
and is about 100 times more sensitive to a single photon than cones.
Note that the responsivity curves presented in the Wikipedia link are normalized. When considering the relative sensitivity of the eye at various wavelengths, we're better off looking at the unnormalized data.