[malloyd]

Originally Posted by Ottriman

This is about vision, I am writing a novel and might also use this for a game at some point.

A character has a power that lets her transform her eyes to replace all the cones with more rods to sacrifice color vision in favor of night vision. We'll assume no neurology problems or anything from this.

You are completely restructuring the nerves and visual cortex of your brain, but for some reason keeping the density of receptors on your retina the same? Why? Shouldn't you consider increasing them instead?

1) How many levels of the Night Vision advantage would that be?

Less than you probably think. You have about 10% as many cones as rods, but rods are about two orders of magnitude more sensitive, so in principle you get about 10 times the light response. But 10 times the brightness isn't all that much by the standards of variation of light levels eyes function in. It's less than +2.

2) If she also added the eye-mirror thing into her eyes that a cat has, how would that affect things. Again we assume no compatability issues.

Not much here either. This basically just gives you a second chance to detect a particular photon that missed the first time (and a cost of blurring the focus of it I suppose). Doubling the light intensity is less than a +1 (about +0.43 for the log ratios).

The fact is human vision (and hearing and touch) are quite good as animals go, and smell isn't bad, particularly for the stuff primates specialize in - we're actually pretty amazing at smelling esters ("fruit flavors"). We tend to exaggerate how fantastic animal senses are.

3) How would you stat this? Something like Night Vision X (Switchable, temporary disad: colorblindness) right?

Sounds right to me.

Edit: 4) What would this look like?

Changing cones to rods is probably invisible without instruments, though maybe somebody with a flashlight peering into your pupil could notice something. A reflective layer is only really obvious in the dark in situations if whoever is looking at you is standing along the line between you and a light source brighter than the ambient light (i.e. pretty much only when the observer is a human carrying or standing in an area of artificial light), but can occasionally glint in moonlight too.