Dr Karl mentioned on Triple J today that the time it takes for an image to be captured by our eyes and sent to the brain can be measured in less than metres/sec and does not transfer at the speed of light. He mentioned that certain things that captures our attention or stimulates the cortex of the eye, have higher speeds than others.
The idea of Lag on the human brain is quite interesting. Here is an interesting article I found in Google on Physical Lag times from Perception to Reaction (although it is unclear on the accuracy)
Human Perception time = 0.1 second
Brain lag = 0.1 second or more
Human Reaction time = 0.4 to 0.8 seconds
Here is a press release (7 Feb, 2002) from Brown University on the discovery of a new photoreceptor and visual system in the eye, which spans beyond rods and cones.