Thank You for your attention and corrections. Please, before adding some more context for my main question, I'll very appreciate if you can tell me the reason is better saying "tell" than "say to", and the same as for "in" instead of "at". This kind of nuances always worries me.
The simple answer is You say something/ / You tell someone something.
John says goodbye. Mother says stop.
John tells Jim to go home. Mother tells Jenny a story.
"at" a point/place = I am at home; You are at school
"in" relates to the interior of something = I am in the house; The words are in the dictionary.
As for "To lock down", it is said in a text talking on the way camera is used in a movie according to the moment. First part has a hand held camera that moves a lot conveying d
ynamism, but when focusing
on a depressed character named Ray..."Ray's life is very static and filled with desaturated colors, so we
locked down the camera. These people live in huge spaces, so we take advantage of the widescreen format. Kind of trying to show the loneliness of it all."
Thank You again.
