Learn Hardcore French: Marie allume sa caméra pour que nous voyions son visage. - Marie turns on her camera so that we see her face.

“pour + infinitive” when the subject is the same in both parts:
- Marie allume sa caméra *pour montrer son visage.*
  (Marie turns on her camera in order to show her face.)
“pour que + subjunctive” when the subject is different:
- Marie allume sa caméra *pour que nous voyions son visage.
  (Marie does something so that *we see her face.)

Here, the subject of allume is Marie, and the subject of voyions is nous, so French needs pour que + subjunctive.

What exactly is “voyions”? Which tense and person is it?

“voyions” is:

Verb: voir (to see)
Mood: subjunctive
Tense: present
Person: 1st person plural (we)

So: (que) nous voyions = (that) we see / may see
It looks similar to nous voyions in the imperfect indicative of voir, but here the context (pour que) forces the present subjunctive reading.

Is “voyions” pronounced differently from “voyons”?

In normal spoken French, “nous voyons” and “que nous voyions” are usually pronounced exactly the same:

nous voyons → roughly: nu voy-on
(que) nous voyions → roughly: nu voy-on

The spelling changes to mark the mood (indicative vs subjunctive) and person, but the pronunciation is the same in most accents.

Why is it “sa caméra” but “son visage”? Both refer to Marie, right?

Yes, both possessives refer to Marie, but in French the possessive agrees with the gender and number of the noun possessed, not with the owner.

caméra is feminine singular → sa caméra (her camera)
visage is masculine singular → son visage (her face)

So:

sa = his/her/its feminine singular thing
son = his/her/its masculine singular thing

The owner’s gender doesn’t change the form; only the noun’s gender and number do.

Could we say “Marie allume la caméra” instead of “sa caméra”?

You could, but it slightly changes the nuance:

Marie allume sa caméra
Emphasizes that it’s her own camera (e.g. her webcam).
Marie allume la caméra
Sounds more like “the” camera in that situation, maybe a particular camera everyone is talking about (a shared device, a room camera, etc.), without highlighting ownership.

Both are grammatically correct; context decides which is more natural.

Could we say “Marie allume sa caméra pour nous voir” instead?

“Marie allume sa caméra pour nous voir” is grammatically correct but does not mean the same thing:

pour que nous voyions son visage = so that we see her face
pour nous voir = in order to see us

The subject changes:

In “pour que nous voyions son visage”, we are the ones doing the seeing.
In “pour nous voir”, Marie is the one doing the seeing.

So if the intended meaning is “so that we can see her face,” you need “pour que nous voyions son visage.”

Why is it “allume” and not “allumer” or another form?

“allume” is:

Verb: allumer (to switch on, to turn on)
Tense: present indicative
Person: 3rd person singular (il/elle/on)

So “Marie allume sa caméra” = Marie turns on her camera.

We don’t use the infinitive allumer here because we need a conjugated verb for the main clause with the subject Marie.

Does “allumer” always mean “to light,” or can it also mean “to turn on (a device)”?

“Allumer” covers both ideas:

To light something:
- allumer une bougie – to light a candle
To switch on / turn on a device:
- allumer la télé – to turn on the TV
- allumer l’ordinateur – to turn on the computer
- allumer la caméra – to turn on the camera

In this sentence, it clearly means to turn on (a device).

Could we say “pour que nous puissions voir son visage” instead of “pour que nous voyions son visage”?

Yes, that’s also correct:

pour que nous voyions son visage = so that we see her face
pour que nous puissions voir son visage = so that we can / are able to see her face

Both use the subjunctive:

voyions – subjunctive of voir
puissions – subjunctive of pouvoir, followed by voir in the infinitive

The version with “puissions voir” sounds a bit more explicit or formal (“so that we are able to see”), but both are good French.