Learn Farsi: در حین نورپردازی، پروژکتور افتاد.

Yes, you could say hengâm-e nur-pardâzi. Both mean "during" or "at the time of." However, dar heyn-e often places a slightly stronger emphasis on being right in the middle of an active, ongoing process (like the physical work of setting up lights). hengâm-e is a slightly broader way to say "at the time of."

If I wanted to say "during the time they were doing the lighting", could I put a conjugated verb after dar heyn-e?

No. Both dar heyn-e and hengâm-e act as prepositions and must connect to a noun or noun phrase using the ezafe (-e). Here, it correctly connects to the noun nur-pardâzi. To use a full conjugated clause (like "while they were lighting"), you would instead need a conjunction like dar hâli ke or vaqti ke.

How exactly is the noun nur-pardâzi (lighting) built?

It is a compound word made of three parts: nur (light) + pardâz (the present stem of pardâkhtan, which can mean to process, arrange, or deal with) + the suffix -i, which turns the phrase into a noun. Literally, it translates to "light-arranging" or "light-processing."

Since the falling happened during an ongoing action, why is oftâd (fell) in the simple past instead of a continuous tense?

The ongoing background context is already fully established by the phrase . The falling itself was a single, instantaneous event that interrupted that background action. Therefore, the simple past () is used for the sudden event, just as it is in English.