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How would you create lightning?

Got a number of scenes in my upcoming film that require a thunderstorm raging outside - I figured the best way to do this is a strobe linked to an audio track (so we can repeat it for multiple takes) - Acme makes a 1500w strobe that can be had for around £70-£80 - what do you people think?
 
Didn't consider the arc part of the welder. Sound wise, a MIG wouldn't be much better, although I always pictured that running outside the window, with the set actually inside. I wouldn't want one around a bunch of gear and people, but as a semi-distant gag. Still though, I forgot about the way an arc works, so maybe not the best idea.

http://www.halloweenconnection.com/detail.aspx?ID=102

(but as a strobe, I have the same worry about cmos rolling shutter ..)

I tested a strobe similar to that recently, and a couple smaller ones as well, definitely sheared as you would expect from a CMOS camera. Interestingly, at certain speeds the strobe would disappear altogether, nothing light by it.

Decay time seemed to be a big factor in getting a photographic flash effect w/o shearing. (maybe not the right word, but easier to say than horizontal banding of light and dark areas, heh) I was trying to get a good looking "photographer's flash" on a cmos camera for a recent project.

flash.sample.crop.small.jpg


These are a couple of quick frame crops. The top frame represents the basic lighting we had going for this shot. The second frame comes after the "photographer" has backed out of frame to take a second picture, and I had one of the g/e guys holding a clamp/dome worklight with an old school 22B flashbulb inside. When he hit the switch the bulb pops. We had a smaller parabolic flash that used press 5/25 bulbs for the prop camera as well, nicer throw with the real reflector than with the worklight reflector, but still works.

After I showed the effect of an electronic flash to the director we agreed that there was no way we could accept the shearing, great if we had a "paparazzi" thing going with lots of flashes, the effect isn't so bad then. But with our photog character being more evenly paced, taking his time, and the only one shooting pics, I really wanted to find a way to fill the whole frame.

I know this is sort of tangential, so I'll bring it back around.

I also used smaller AG-1 bulbs for some effect flashes. These are stupidly easy to rig. Small alligator clips from RadioHack and some light gauge speaker wire are all you really need. Supposedly you can get them to pop with around 3v or so. I used 9v batteries just to be certain.

Someone with more knowledge than I could probably rig something with these to get multiples of them to flash at some sort of lightning like intervals and combos.

The trick is finding them. :(

Edit:

Wow, I really have completely forgotten how to punctuate a train of thought. The funny thing is I know what's up there is rough, but no clue how to fix it anymore. :lol:
 
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It seems to be, but I only tested on one camera, so not sure how others would respond. Similar I imagine.

Before I start mis-using terms, I guess the duration of the whole flash event is the significant item. These seemed to be around 1/30th second, with probably some variation from bulb to bulb. I haven't seen any that are partial frames, but some are only a single frame flash, others start/end more gradually, lasting a couple of additional frames.

I don't know if it's the real "key," though. They are difficult to find, and you have a delay from one flash to the next as bulbs are swapped. I know the a1-g (little ones, like the kind found inside flashcubes) can be used for all sorts of things, they also seem to have a slightly longer duration (still speaking in the 3-4 frame range from strike through flash to fade out) than the other ones for some reason, in general.
 
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I am having the same problem. We are shooting an action film with lots of nighttime gunfire and some explosions. The needs of directional light is great and you just can't do it in post.
I will need lots of flashes close together and some really powerful ones. It seems arc are the only option besides real blanks.
I have an arc welder and will look into that. I also read a DYI somewhere about using carbon electrodes form the large square batteries and powering them with a car battery. But now I can't find the reference.
 
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