Hmmm.. that makes no sense.
Without a Bio Preds see completely red. They only see other spectrums of light (infra-red etc.) WITH the Bio. According to Predator 2 at least (even though there's an error when P2 sees Harrigan in infra-red without his Bio). So that's kinda weird.
But yeah, I've seen numerous pics of Machiko on here and until Cajunsith mentioned it I never noticed her eye. Can't blame me though..
Makes no sense?! It makes no sense for it not to make sense. Predators see in infrared no matter what. The way their vision is portrayed has never been consistant though.
"We're fairly certain this being can see in only one spectrum of light--infrared. He hunts by seeing our heat." -Peter Keyes in Predator 2.
The bio just filters the light for them and allows them to see in other spectrums. On a personal note, I think the infrared would be cool as just a Bio feature, but it makes no sense the rest of the time, especially when their prized trophies would not give off any heat, but are clearly there to be admired by other Preds. It's a flaw in the character design from the beginning.
For Machiko to have one eye modified to pick up heat makes total sense. Yes, her Bio should do that for her too, but she won't always have it on. How many hunts have we seen where the Pred has the Bio on at the end, right?
Come to think of it though, this vision would not work for Alien hunting anyway. The Aliens don't show up on infrared.
"Switch to infrared, people." -Sgt. Apone in Aliens
"Maybe they don't show up infrared at all." -Cpl. Dietrich in Aliens just before the Alien she just looked right at drops down and grabs her as she turns away.
Even Scar had to switch modes to see them in AVP, which means he shouldn't have been able to clearly see the Queen at the end of the movie.
If they do end up remaking Predator, I hope they rethink the vision problems.