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Old July 29th, 2004, 04:53 AM   #1
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Gelling out windows for DV

I was wondering if there was a guideline for gelling windows that are going to appear in frame on DV so they don't blow out. Charles I know you had a ND.9 on them (er three nd.3's) this weekend for a noon time shoot, is that typically what you go with for that time frame or is it more of a pure trial and error sort of thing?
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Old July 29th, 2004, 12:09 PM   #2
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You could also cover the windwo with a black net fabric to nock down the light

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Old July 30th, 2004, 12:23 AM   #3
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Hey grason thanks I was looking for something that would allow me to see through the windows without blowing out the picture. Just wondering if there is a rule of thumb (like noon nd.9 or your picture will be blind, dusk nd.6 unless you're faicng west,) that sort of deal...
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Old July 30th, 2004, 10:30 AM   #4
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Hi Nick:

It all depends on what you see outside the windows. In that instance we were looking at the side of a house that was white, but in full shade. A darker colored house might have called for less ND; if it had been in sun, more ND. And it also depends on how hot you want it to appear on camera. Usually I read the exterior with a spotmeter to make the call on what level of ND I want to use; in that particular instance I did the quickie method of aiming the camera at the window and dialing down the iris until I liked the exposure outside, then doing the math compared to the iris setting I had chosen for the interior scene. In this instance, the difference was 3 stops, so the ND.9 covered that.

So obviously, there are too many variables to really land on a rule of thumb. Had that house been angled differently or if it was an hour later, the sun would have crept up the wall and we would have been looking at at least 2 more levels of ND. And of course, the level of exposure you create inside the room will be another end of the equation. A small lighting kit wouldn't have brought us to the same stop offered by the 1200 and 575 watt HMI's we were using on that scene.

I was actually annoyed at myself because I have a roll of Roscoscrim, which is a perforated black material that achieves the same sort of thing as multiple layers of ND, and you still see the image through the holes. I had simply forgotten to bring it that particular day.

Grayson's suggestion for using black net is indeed valid; you can see and photograph through it, although once you start doubling it up it is possibly to create unwanted moire patterns. On other days on that shoot, Nick, we used double nets folded over twice to knock down large portals such as exterior doors (a double net=1 stop=ND.3).
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Old July 30th, 2004, 10:49 PM   #5
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charles, thanks, I think I was looking for the non spot meter approach adn the point and shoot then dial down of the iris was the ticket. I also always forget how much.nd = a stop of light so one nd.3 gel=one double net piece of fabric=one less stop of light. (which is a t-stop correct?)
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Old July 31st, 2004, 12:13 PM   #6
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Yes, those numbers are correct. The only thing about a loose (6x6, 12x12) double net is that it is approximate where the other factors are pretty well absolute. The net can be stretched or bunched up which may affect its transmission. But a mounted, 2x3 or 18x24 double net is supposed to equal one stop.
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