Hello again. I didn't think I'd be back so soon but I've got a dilemma.
I completely understand the Inverse Square Law, and how/why it works with lighting units. What I am currently having trouble understanding is why the Inverse Square Law (ISL) does not seem to occur in reflected light bouncing to the eye/camera or when viewing apparent surface brightness of a source.
A theory I have is the ISL does effect the reflected light we photograph and see, but it is negated since moving away (which should reduce the light) only needs the light energy over a smaller area of the negative. In turn, moving closer to the reflected light source (which should increase intensity) requires the light to fall over a greater area on the negative, again negating the effects.
If this is correct, and I have answered my own question, I still have some issues with this theory.
Why does my reflective light meter read the same F/stop when I'm 2 inches or 20 feet away? I loaded a white screen on my laptop, and took a reading from literally against the screen, and then another about 20 feet away (before the spot meter angle of view was no longer good) For both readings the screen filled the entire spot meter 'frame' and gave the same exposure.
I'm also racking my brain on how this would apply to zoom lenses. The lens could enlarge the reflected light upon a greater area of the negative, yet not gain the increase in light because it didn't move forward.
I guess I'm looking way beyond what is necessary, but it boggled my mind that reflected light doesn't appear to be effected by distance which breaks the ISL.
I have a some questions about pre-production. How do you do shot lists? Do you go to all of the locations with the director and talk about every shot in the movie before production starts? At that time, do you and the director figure out blocking, and do you also decide how to light each shot? What notation or documentation do you produce to describe this? Is this documentation that the gaffer and key grip can read directly? How do storyboards come in? Do you take stills to give to the storyboard artist, or do you describe each shot to him/her?
First of all, remember that Inverse Square Law only applies to a point source. But even broad sources suffer from fall-off.
But as for why your eyes and a camera lens does not see reality fading into darkness as objects recede, I don't know the scientific answer but I would guess it is because your eye or the camera lens does not need or use the volume of light reflected by an object, it is focusing a few photons through a lens, so it doesn't matter as much that a lot of other photons are scattered and lost over distance. Your eyeball isn't being "lit" or exposed by all the bounced light off of an object, it is taking a picture using only a few representative rays of light coming from the subject. That's a guess though, because it's still confusing when you think about it. I mean, I assume a point source of radiation (visible electromatic radiation in this case) behaves according to the inverse square law, but a single stream of particles (photons, electrons, etc.) doesn't. So how does a laser beam behave? They seem to travel much further than a typical light so perhaps because of a lack of scatter, they don't follow the inverse square law as much.
You basically prioritize -- you start by discussing (between you and the director) the most complicated sequences, breaking them down into manageable shots. If necessary, you storyboard them because you want people to see the graphics of the sequence, what might be in the background, etc. Less visually intensive sequences can be shotlisted. Less complicated scenes, well, you can be vaguer about the shot list.
Sometimes you have a dialogue scene with a lot of actors moving around a space and you decide that you need to block it out with the actors in a rehearsal, you can't adequately predesign the blocking without the actors' input. So you try and be aware of the time restrictions in which you have to shoot and cover the scene, do the blocking rehearsal, and then quickly break it down into shots right then, sometimes the script supervisor taking notes.
But if you do that, go without a shot list, at least try to make a guess at special equipment needs that may require some prep, some advance work to organize. You don't want to block a scene on the day and then decide you need a Steadicam, if you aren't normally carrying one (and even if you are, you want to plan on the time it takes to set-up.)
Shot lists can also be a bit pointless if they are unrealistically long, because you may end up redoing the list on the shooting day anyway to make it realistic. Slightly long is OK if the director can separate the "must haves" from the "nice to get" shots, i.e. prioritize.
There is an old saying that on a film shoot, it's " 'Gone with the Wind' in the morning and 'Dukes of Hazzard' in the afternoon" -- that you spend too much time in the morning and you rush like mad in the afternoon to make up for it.
In other words, you always have less time than you think, and if you think you are on schedule, it means that you are probably behind schedule -- so just assume you are behind schedule.
More often than not, a simple shot turns out to be harder to shoot than planned, so give yourself some wiggle room in your shot list.
It's not a bad idea necessarily to shot list the whole movie because it's like a first draft, one pass at breaking down the movie into images and cuts. That can be enormously helpful for simply getting to know each scene and its dramatic intent -- even if ultimately you find yourself deviating from the shot lists. But it takes a lot of time to go through a whole movie in such detail, and if you start at Page One (not a bad idea) you may not make it to the last page. So I would do the opening and closing of the movie, and key scenes in between, and then fill in the gaps if you still have time.
^ That is my best guess, too.
Thanks for the replies! It's a tough question I've been banging my head against for the last day. I was posting here hoping for a 'hail mary'.
This discussion was from a different website, which I take part in and the thread was quickly hijacked by this intriguing need to know why.
I still do not understand how the spot meter doesn't account for distance differences, but your answer I think has given me a better idea.
I think it's partly about how focussed the light is. As in with a laser, it doesn't seem to get dimmer as quickly because the light is coherant (meaning all going in the same direction). With a lamp the light is getting tottally scattered, less so with a fresnel but still pretty much scattered, the same with a reflected light source like some white card or an actor. When a light is shone right in your face it feels much more offensive than when it's far away, but kinda looks just as bright.
I'm not sure I'm really getting at anything here. But yeah, I guess the fact that when something is further away, it's smaller amount of light is filling up less photo-sights or photoreceptor cells so that compensates.
Edit: perhaps the spot meter is being "polluted" by nearby light?
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