Staring into the Sun

Question: If a Scion with the Sun purview stares into the sun or any bright light that would normally blind a Scion lacking the Sun purview, would it stand to reason that the scion that has the Sun purview would be able to see perfectly fine without any hindrances?

Not necessarily. Simply having Sun will not make you immune to any and all lights, the same way that simply having Illusion will not make you immune to all illusions or having Animal (Bear) will not make you instantly bear-proof. Some purviews have no immunity boons, or express them in different ways (i.e., you can command the bear not to hurt you, but you'll have to beat its roll); others specifically have immunity boons that allow you to ignore the effects of that purview's powers and energies, and those are the ones you need to try to pull off being able to shrug away anything that the purview might control. A Scion with Sky who doesn't take Electrical Immunity is going to be just as susceptible to lightning bolts as a Scion without Sky, because he chose some other powers to represent his control over the purview.

The Sun purview does not technically have an immunity boon, mostly because the problem of light overload is usually covered with Stamina + Fortitude or Perception + Awareness rolls; because withstanding simple brightness can be covered by those mechanics in a way other purviews with immunities can't (for example, you can't Stam + Fort your way out of being on fire), it's not as necessary for there to be an immunity boon, especially since one would probably come up a lot less than mosst other immunities. For most characters, determining how much you can see when there are very bright lights impeding you is a matter of having a high enough Stamina roll to avoid being blinded and/or a high enough Perception roll to see despite the glare.

However, if you happen to have Penetrating Glare, some Storytellers do allow it to function as a sort of light immunity for those Scions who have purchased it. While we don't technically have that built into the boon for the reasons above, we do occasionally allow it with a good stunt, when a Scion does something particularly neat or unexpected with his affinity for sunlight. A Scion who's just squinting at something on the horizon while the sun's there probably wouldn't get anything from us, but one who describes how he opens his eyes wide and they take on the golden sheen of the setting sun while tears pour down his cheeks from the light et cetera will probably get a pass (or at least some stunt dice to mitigate the normal penalty for effects that make it hard to see).

Even if you do prefer to use Penetrating Glare as an immunity boon, however, we'd suggest limiting it to normal lights and situations most of the time, or at most only to other Sun boons. Your powers over the sun should not make you immune to being blinded by a Sky god's lightning bolt hitting you in the face or a Star god's flash of blinding whiteness; those are magics that are clearly not covered by your powers over the sun, and a boon that could do that would need to be significantly higher-level than Penetrating Glare currently is. If you did choose to expand it to all lights, I'd suggest removing its power to see in low light in order to balance it out a little better, and letting Scions with Sun roll their Perception + Awareness like everybody else when it's mostly dark.