Breakdown of Я сказал, чтобы оператор проверил свет.
я
I
свет
light
сказать
to tell, to say
проверить
to check (perfective)
Questions & Answers about Я сказал, чтобы оператор проверил свет.
Why do we use the past tense проверил (checked) for a command like 'to check'?
Why is it оператор (nominative) instead of оператору (dative) if I am speaking to him?
Because in this specific Russian sentence structure, you are not saying 'I said TO the cameraman.' Instead, оператор is the subject of the second half of the sentence. Since he is the one doing the checking, he must be in the nominative case.
Could I use the infinitive проверить here instead of the past tense?
No, because the person speaking (I) and the person checking (the cameraman) are two different people. You only use чтобы plus the infinitive when the same person is doing both actions, for example: 'I came in order to check.'
Why doesn't the word свет (light) change its ending?
The word свет is in the accusative case here because it is the direct object (the thing being checked). However, because it is an inanimate masculine noun, its accusative form is identical to its basic dictionary form.