Human eye versus the CCD camera

I was standing on the top of the 8 foot solid concrete ceiling of the linear accelerator. My advisor excitedly looked through the pipe into the accelerator “cave” below. He looked back at us smiling, “I can see it with the naked eye”! What he saw was radiation emitted by an electron beam when it passed through a thin film. The human eye can detect almost single photons of light! I looked through the pipe as well and could clearly see the purplish white light coming from the thin film.

I was quite intrigued. I had never thought about how sensitive the human eye really is. We had two very expensive Charge Coupled Device (CCD) camera. In those days, digital cameras had not become consumer technology. And in any case, we were using one with high sensitivity, designed for scientific applications. At $25K a pop, weighing several pounds and liquid cooled, it wasn’t quite what you’d carry in your pocket to snap a picture the Grand Canyon. It was the most sensitive camera you could buy on a reasonable lab budget. And yet it was less sensitive than the human eye. And of course, cameras have a hard time matching the dynamic range of an eye.

My advisor’s comment got me thinking about how all our technology doesn’t even come close to mimicking the functions of an animal or human body. Robotic dogs, pneumatic hands, etc. all only estimate some aspects of behavior of natural bodies.

These were pre-Google days and though Alta Vista existed, just because I had a sudden interest in the sensitivity levels of the human eye, I couldn’t expect to find a gigabytes of layman-level information on the human eye just by searching for it on the internet.

Evolution of the eye is a topic that has been hotly debated because of how complex the eye is: So many different functions and muscles had to evolve to give us a functioning eye.

Last year, Edge, a forum which brings together the world’s leading scientists and thinkers, published the transcript of a series of dialogues on evolution of life. What I liked about the series is that it was conducted in the form of a round-table. In each session, one scientist presents his views and the others chime in at various points to raise questions or emphasize some points. So instead of a boring highly structured monologue, we read through a discussion in the form a train of thought. Link.