[WhoBeI]

Night vision uses the photoelectric effect to translate a few photons from the lens into a picture you can see. It doesn't change the frequency of incoming light - it absorbs it and transmits an electron. Basically you are carrying around something similar to an old style tv on your head.

[possibilistic]

Photoreceptor proteins, such as rhodopsin (typically the first GPCR [1] you'll study in a biochem undergrad program), each have different characteristic absorption spectra. But it's much more complex than that--each of these proteins exhibit different absorption spectra given different isomerizations and even different conformers [2] .

Here are some absorption spectra [3] of crystals of various rhodopsin isomers. I'm not sure if any of these are biologically relevant isomers, but it's interesting that these were not in solution. (I suppose that since they're membrane-bound GPCRs and might be difficult to study in solution? This isn't my field of study.)

Check out some bacterial absorption spectra [4]. Visual perception isn't limited to organisms with eyes. Or even eukaryotes, for that matter. It's actually pretty ancient [5].

On that note, pigment chemistry is pretty fascinating.

1. http://en.wikipedia.org/wiki/G_protein-coupled_receptor The GPCR family is really cool. A ton of our sensory perception arises from class A GPCRs. Here's a really beautiful diagram of the 7 transmembrane regions of rhodopsin: http://physrev.physiology.org/content/physrev/81/4/1659/F1.l...

2. http://www.sciencedirect.com/science/article/pii/S2210271X13... Just to cite an instance, though this one isn't vision-related.

3. http://www.pnas.org/content/103/44/16123/F1.expansion.html

4. http://group.szbk.u-szeged.hu/ormosgroup/abs/abs.html

5. http://en.wikipedia.org/wiki/Archaearhodopsin