During all this discussion I hadn’t thought about how little experience most of us have negotiating around outside in the dark, so a couple of tips may help with spinners and other things. This may be off-topic, but if it saves one of us from having a broken ankle it isn’t wasted. As Nightfisher pointed out, we need to use our peripheral vision after dark.
Though the eye receives data from a field of about 200 degrees, the acuity over most of that range is poor. To form high resolution images, the light must fall on the fovea, an area of the retina having a high concentration of cone cells, and that limits the acute vision angle to about 15 degrees. In low light, this fovea constitutes a second blind spot (the first being where the optic nerve enters the retina) since it is exclusively cones which have low light sensitivity. At night, to get most acute vision one must shift the vision slightly to one side, say 4 to 12 degrees so that the light falls on some rods.
Since the fovea provides the sharpest and most detailed information, the eyeball is continuously moving, so that light from the object of primary interest falls on this region, cone cells in the fovea are individually connected to nerve fibers.. ...the rods (B&W vision), on the other hand, are connected in groups to nerve fibers, and a single such fiber can be activated by any one of about a hundred rods. The actual perception of a scene is constructed by the eye-brain system in a continuous analysis of the time-varying retinal image; apparently, also not unlike the night vision of a trout. The exception is that trout has rod cells in the central portion of its visual field. While we cannot look directly at an object at night and expect to obtain any visual acuity, a trout apparently can.
To obtain and keep your night vision will take about twenty minutes with no exposure to any obvious light source. Any exposure to a bright light will destroy the sensitivity of the rod cells, and you will have to start over. A soft red light source can be used to assist in seeing surroundings most easily, but this light can be seen by others (fish?) just as well. Some caution should be exercised to shield the light source from direct exposure to the water. However, even after having extensive training in the subject, I must point out that I have lost the desire to stumble around in the dark with my companions after having discovered the social advantages to barbequed meat and strong drink.
John