Photoreceptor Size

Length scales in bionumbers allow a deeper understanding of the eye. A rough estimate would take a human rod to be $10^{-6}m$ ($\mu m$) in diameter, giving approximately 250,000 rods per $mm^2$ into 500x500 blocks. Since the back of the eye has about 2-3cm diameter, there are roughly $10^9 \mu m^2$ TODO(why divide by 4?), giving 200M photoreceptors per eyeball.

The Samsung S21 ultra has about 100M pixels, so smart phones are catching up to the data size that the human eye is capturing.