#2. "RE: Christmas lights w/ D5100 in Movie mode " In response to In response to 0
Well, you do have three months and you aren't using film that has to be developed so this should be easy. Get a string of lights and start this weekend.
Seems to me that taking a picture of a light source requires a lot less exposure than trying to take a picture of something iluminated by that light source. So you should be able to stop down the lens which gives you greater deapth of field.
Assuming that you want to capture relatively large arrangements, from the whole display to sections of the display, you will be relatively far away from the subject. This also enhances deapth of field.
So. Take make a quick video of your lights (at night) from various distances with various f/stops at each distance. This will tell you your maximum f/stop (smallest apperture) for each distance.
Assuming that you will have to go across the street to get a shot of the entire display, set up some kind of focusing target one third of the way back from the frontmost part of the display (on the assumption that the deapth of field extends 1/3 forward of the actual focus point and 2/3 behind it - if the experts know different, please help out with the correct numbers). Focus on the target from across the street and mark the lens or make a note or something so that you can return it manually. Also note the location of the camera so you can return to it when you do it for real. (This focusing can be done with AF-S. When you do it for real, everything will be done in manual mode)
Repeat the above process from any other point from which you might want to shoot portions of the display.
You may also want to consider that the house will be illuminated by the display at some level. The adjustments that determine from the previous steps may not allow the house to be in focus, so you might also want to repeat the steps to determine focusing points which would bring the house into the deapth of field zone.
I have never done anything like this, have had my 5100 for about a year and have only been getting the hang of it within the last two months or so. However, this is how I would approach the problem.