
Volkard Abendroth |

Well, we have this line: "The synthesist wears the eidolon like translucent, living armor." Translucent, so light can pass through.
You Keep Using That Word, I Do Not Think It Means What You Think It Means
What you are describing is the word Transparent.
Translucent blocks some (e.g. olive oil), or even most (e.g. dark sunglasses), of the light. Humans, for example, are translucent. Don't believe me? Go in a dark room with a flashlight, turn it on, and put your hand over it. Some portion of the light shines through your hand.
That said; the synthesist retains all of his own abilities not explicitly replaced. This includes both his special abilities and his weaknesses.

Zwordsman |
Off hand I'd say no,
simply because the phsyical stats are replaced and overlaid.
quite a few things in real world let light through but also filter out vaarying properties of light.
but mostly because the rules set replace the physical and as far as I know, even with poison, the synth can't be effected by things until the fusion is broken/dead.

Omnius |

What you are describing is the word Transparent.
Translucent blocks some (e.g. olive oil), or even most (e.g. dark sunglasses), of the light. Humans, for example, are translucent. Don't believe me? Go in a dark room with a flashlight, turn it on, and put your hand over it. Some portion of the light shines through your hand.
For most practical purposes, in normal, every-day lighting, humans are functionally opaque.
Unless we're in a scientific setting where such fine details of optics are important, a human is opaque.
If they actually bother to describe it as translucent, then that is supposed to convey some meaningful content to us, not be some nebulous technicality if you shine a super bright light behind the synthesist in a dark room.
If they're saying it, then it's safe to presume it's noticeable.

avr |

Exposing any vampire to direct sunlight staggers it on the first round of exposure and destroys it utterly on the second consecutive round of exposure if it does not escape
direct sunlight
if it passes through the eidolon it's not direct anymore.
So it would not hurt the vampire.
A vampire dies if there's only a glass window between them & the sun in the source material. I'd choose to interpret the rule in a way consistent with that, i.e. the eidolon-suit won't be enough.

Lady-J |
well it depends what kind of vampire we are talking about, if its based on the more modern interpretation that its the UV rays that kill them then yes i would say the edolon protects the user from the UV rays. personally i'm of the mind set any vampire with a weakness to simple sunlight, water or silver is a pansy and not a true vampire and change all my rules for vampires accordingly.