jon_slater

I mean like several photos that can't be retrieved. What have you done with them?

I'm still a PS neophyte. Rods see luminosity and some contrast. Cones see in RGB. Cones are about 300 times less sensitive to light than rods. According to Guyton's textbook of physiology, the human eye can change it's sensitivity to light by as much as 500,000 - 1,000,000 times. It's an interesting topic - wonder when we'll have biologic sensors in our cameras?

Jon

I'm still a PS neophyte. Rods see luminosity and some contrast. Cones see in RGB. Cones are about 300 times less sensitive to light than rods. According to Guyton's textbook of physiology, the human eye can change it's sensitivity to light by as much as 500,000 - 1,000,000 times. It's an interesting topic - wonder when we'll have biologic sensors in our cameras?

Jon

Justin,

I'm not sure what the dynamic range of the human eye is, or how you'd even measure it. I'll try to reach for an answer. For the benefit of those who don't know, the human retina has two types of photosensitive cells. Rods are sensitive to luminosity and are found over all parts of the retina except the macula where your eye focuses for detail. They have a wide range of sensitivity, and are responsible for night vision. Thus at night, you don't appreciate colour, and you can't really see something you look at directly.

The macula only has cones. Cones are sensitive to colour. They require more light to be active but are sensitive to a much wider range of light than film or CCDs. Basically, if you can read, you're using cones to do that task.

However, since you can only focus on one area at a time, you won't really notice detail in the other areas. So the dynamic range of the human eye could be considered very limited in that respect.

I'm not sure if I've clarified or confused the situation, but that is my limited understanding of the subject.

There's a good discussion of this on Luminous Landscape http://luminous-landscape.com/tutorials/expose-right.shtml

Jon

I've noticed that the requirement to post a comment when giving

ratings of 1,2 or 7 has been dropped. This has led to perhaps more 7s

being given, but it has also led to an increase in drive by ratings

with 1s and 2s. Without comments they do nothing to help improve

photography. I'd appreciate a return to the former policy.

Jon Slater