Ok this might be a weird question. I have always wondered does the Predator actually see through the lens of his mask or is that like a camera that looks like eyes but the picture is actually projected in their head like Geordi La Forge's VISOR on Star Trek.
I would imagine they see through them, but the lenses definitely filter light for them depending on how they want to see. In P2, in the slaughterhouse, the Pred shifts filters until he can see the ultra violet lights the insulated team is using. In its usual infrared hunting mode, they were invisible.
Scar also shifted filters to see the Aliens in AVP. As mentioned in Aliens, "...they don't show up on infrared at all."
Why do all the aliens look differently from movie to movie? Is it because copyright issues or each director uses creative license?
Luis
There are speculations,
A Directors have different views on how Aliens should look.
B It's also said Aliens pass on genetic information through the generations.
B is an excuse to justify A, but both are correct.
When I went to Monsterpalooza last month in Burbank, California and I saw the ADI guys, they even said that many of their best designs get shat on by the directors who have other ideas (PredAlien final design was not ADI's choice) or the producers who feel a certain design creates budget concerns (apparently the alien suits in Race to Witch Mountain with the Rock were supposed to look way cooler with crazy lighting effects).