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Shooting ExplosionsFancy a giggle?
I hope you can help. To improve image quality we can choose not to use a protective port on the camera housing on the ground floor and write off the lens. The interior ground floor shot needs to be quite wide, 100 degrees, so a 1 inch thick laminated filter will degrade the corners of the frame as well as require a much larger camera housing. Any ideas for keeping dust off the lenses? Lighting for the ground floor interior has presented a big challenge. The lighting ideas so far are:
D) Same as C but place lights in holes in corrugated iron. They would be much farther away from pillars so we would need many more. I Can't be more precise until next week when we have anothe recce. But they would be a further 20 feet away from the blast so may last a few seconds longer. E) Combination of the above. The unknown factor in this shot is of course dust. Will it obscure the collapsing pillars? UK Broadcasters are particularly touchy these days about filmmakers interfering with documentary subjects. So we have to shoot this for real. We cannot even cut-in a big close up of an exploding pillar, shot in another place. Pyrotechnics, for some added glitz, are out of the question too. We will be satisfied just to get the beginning of the explosions Mike Brennan >Any ideas for keeping dust off the lenses? You could blow compressed air towards the lens flats. As far as lighting, how about an array of china lanterns sporting 1000 watt bulbs? Obviously you won't have to worry about the lanterns catching on fire, and they're reasonably small so they won't obscure the view of the crumbling pillars. They are also quite bright and very cheap. Depending on how fast your lenses and film are and how large the interior is, the lanterns may provide enough light. Perhaps a combination of lanterns and ekiM. How about the Hydroflex mattebox with a small tank of air (like those emergency scuba outfits?). I've used this with a low angle, very dusty dirt road situation to good effect. Alan Caudillo We have two shots to deal with, one is a camera on the 20th floor, positioned on a pole about 8 from the parapet looking vertically down. When I did this a few years ago the port became a little dusty 1/3 of the way down, with fine particles sticking to the filter, 2/3 of the way down the camera hit the rising cloud of dust caused by the lower 20 floors impacting the ground. This dust cloud was very dense and as the camera was moving at about 30 mph it was instantly smeared by larger particles of grit that would be probablyimpossible to remove with compressed air. An onboard system to clean the port for the first 3 seconds would be useful. A can of dust off sounds ideal but I am worried that if the can became inverted the propellant would be expelled and therefore, ice over the port!
The cameras on the ground floor can have a pressurized supply of air no problem. Has anyone tried this under very dusty conditions? The duration of the shot is hopefully 3 seconds at 500 fps (1/2500th sec) on one camera and 1000 fps (1/5000 sec) on another for a close up, lighting budget permitting. Mike Brennan >Has anybody come across a pressurized dust off product that does not contain a >propellant? Falcon made a nozzle that was attached to a hose, that was in turn attached to the can. That may be what you need. The can can remain vertical and the nozzle moved around and positioned where you want. D) Same as C but place lights in holes in corrugated iron. They would be much farther away from pillars so we would need many more. This sounds very exciting visually wise, especially when the dust first begins to rise. I guess in this case the old standby advice "TEST TEST TEST" doesn't apply. Steven Gladstone EkiM wrote : Thanks, that a good idea and cheaper than 10k bubbles and holders, (£180 for a 10k bulb and £40 for holder) The concept of 60 to 100k of tungsten in the same area as detonating cord and explosives has still be addressed by the demolition team!
Mike Brennan
For the dust...creating a very high pressure zone in front of the flats would be my choice. In my non-linear editor I have 5 12v cooling fans that move 100 cuft/min each. If four of these were mounted in ports on a hard matte box that was sealed to the flat, each with its' intake side covered with fiberglass wool so you are not re-circulating dust, powered by a car battery.....it might do the trick. For light...flo's/nook lights/bare bulbs mounted on the backside of the pillars and above the cut line of the explosives....they will put some light the next pillar in line, provide some shape to each explosion and by lighting the developing dust clouds behind each pillar, will create a lighter valued background, making it easier for the pillars to stand out.....for awhile at least. With whatever approach you choose, lighting the clouds of dust should be part of what you do. How about putting some cheap laser pointers in there.....attached to the pillars you can create a grid in the smoke that may give a nice visual of the collapse when the smoke has obscured everything else. Glenn Suprenard Dir/DP >Auto racing ran into ( pun intended) a similar problem, and came up with a moving >shield.
ekiM. .25" clear polycarbonate plastic would be good for protection "if" it is well secured so that it doesn't implode into the lens. The unsupported area of the filter should be as small as possible to reduce the amount of pressure it has to withstand. The amount of distortion might be acceptable even with a wide lens. One problem is that it does attract and hold dust more than glass.
>Any ideas for keeping dust off the lenses? Air nozzles is a good solution. Props dept. has done this for us. We had to use two wide fan shaped nozzles with a lot of pressure to keep the dust off. This one you can test out before hand. >Lighting for the ground floor interior has presented a big challenge. Others have suggested quartz halogen T3 bulbs which come in at least 1500 watts. This sounds like the least expensive way of doing it (the cost about $15 each here in the US). A sheet metal shop should be able to make some inexpensive reflectors. Good luck & have fun! Don Hayashi >Auto racing ran into ( pun intended) a similar problem, and came up with a moving >shield. Panavision has one of these devices. I saw it used to prevent water from >splashing on the lens.
On the subject.... Did I read correctly in a prior post that you are considering the use of HMI lights with a prism/drum camera at ultra High speeds? Am I wrong in thinking that this isn't possible, since your fps rate will far outstrip any kiind of AC arc light, flicker free or otherwise? Have you discussed any options with your pyrotechnical folks about the possible use of something like magnesium flares as a lighting source? If they lay them down as part of the "charge", are you still subject to the admonishments of documentary purists. I'm not sure if I'm ready for that vow of chastity, myself. Hope your shoot is a real blast! Joe Di Gennaro >Am I wrong in thinking that this isn't possible, since your fps rate will far outstrip any >kiind of AC arc light, flicker free or otherwise? I have shot at 1/5000 sec shutter speed with my Arrisun 1.2 flicker free. Thanks
How about designing a rig that blows pressurized air across the lens with the air piped-in from a compressor off-site or next to the camera? Also, I recall seeing promo literature awhile back for HMI pars (4K-6K?) that were designed with both underwater housings and explosion housings. Jim Sofranko
I'm gratified to hear of your success with flicker-free HMI lights and prism/drum High speed. I'll be tempted to try it on my next Photosonics gig. I thought further about your needs for a somewhat expendable, powerful light source: Joe Di Gennaro
From what I've seen watching doc's on demolitions...they blow the pillars in What would it take to mount the camera on speedrails and get up enough speed Anyone belong to an amateur rocket club? Glenn Suprenard Dir/DP >How about designing a rig that blows pressurized air across the lens with the air >piped-in from a compressor off-site or next to the camera?
>What would it take to mount the camera on speedrails and get up enough speed to start rolling on the first pillar and back out of the building just ahead of each explosion, staying just infront of the dust cloud. Anyone belong to an amateur rocket club? Come on Glenn, you know you want to be in there on a dolly with a grip pushing you, the Ultimate one take shot. Steven Gladstone
Didn't think I was being that obvious. Hey...ya' know those cable rigs they use to yank stunt people off horses or launch them during explosions. Heck, with a pulley system, a couple hundred feet of cable, a hundred foot crane and a few hundred pounds of counter weight ..why...you could shoot this hand held. Glenn "Ready when you are C.B." Suprenard Dir/DP Mike you said for a giggle !! Well from Justin's "Stupid ideas R us" file comes this one :) Get Kodak to let you have a length of safety base as long as your drop and 70-80mm wide. Work out a channel for this past the lens and a feed canister on one side. Either pull it past the lens with a motor or (better I think) attach the free end to an open umbrella. This would have the advantage that it would go quicker the further it has fallen also you could extend a bit of string to the top of the building so that the umbrella would not get stuck with the falling masonary ... No I'm not drunk I'm like this all the time. Justin I had thought of a more British way to create the same effect- a bungy rope!
Mike Brennan
Mike Brennan
Get the camera rig moving before the first explosion to get up to speed and even if the explosions catch up to the camera, that would be a nice shot. I have made a tube dolly with opposing concave wheels, the dolly platform was a high hat on a pancake. The tube was PVC and the dolly was mounted from the end of the track and locked onto the tube. If you attached your bungee to this, left the end of the track open with out a stop and at building opening, it might build up enough speed to launch itself clear of the building. Think of it as a slingshot. Also, if the dust from the explosion is going to limit what you can get, why not shoot on the floor above. The building collapse could be thought of as a more important theme than the explosions that started it. Glenn Suprenard Dir/DP >Is there a way of remotely trimming carbon arcs? Actually, there is. The anode and cathode rods are fed into the lamp housing by a pair of corkscrew like devices, which act like slow turning electric pencil sharpeners. The problem is that the longest rods I know of will only burn for about twenty minutes. I don't know of any way to remotely strike the arc. I'm not sure if your demolition engineer will be knowlegable/comfortable striking up. Perhaps someone like Mark Weingartner can offer some advice, having been a sparky kinda guy for many years. Sincerely, Joe Di Gennaro Regarding lighting the demolition of the pillars in the boarded up ground floor. You might consider magnesium flares. They last for several minutes, they create a tremendous amount of light, and are disposable, so there is no great expense of trashing a lighting fixture. Of course you would have to do some tests to see just how much light they make. And also to see if the explosion shockwave will "blow out" the flare, but I doubt it would. Once magnesium is ignited, there is not much that will put it out. You will have to develop a remote method of lighting the flares. I've never done this, but it seems like a great way to make a tremendous amount of light, in a reliable manner, for relatively little money. Bill Bennett
Jim Sofranko Hi Jim,
Jerry (speaking for myself, as usual) Wolfe
One small point. I seem to remember from filming in a quarry that all the force should be held within the object being blown up. So a well controlled explosion is rather unspectacular a all you see is the rock face slowly separating from the rest of the quarry. Still, I'm glad that OpTex doesn't have high-speed cameras, I think I'll give this one a miss!
YeeeOoouch! Yeah I recall working with the smoke and sparks of the early HMI's as well as those huge, heavy ballasts. Amazing how much more durable and lighter HMI's have become in recent years. Jim Sofranko
Magnesium creates its own oxegen when ingnited. It burns fully submerged in water. caleb, New Orleans based, has shot by 'Flambe' during Mardi Gras
>I can't help feeling that we are all referring to HMIs that are sufficiently sealed as to >be 'intrinsically safe' ie they won't cause an explosion in an explosive atmosphere. I think someone needs to explain the misnomer "explosion-proof".
As for the current issue of filming a building demolition, I would first talk to the demolition team themselves. Most of these outfits regularly film or tape their work, partly for the publicity and partly to study the blast process itself. They may have plans to record the event themselves, or at least have experience with recording past building removals. Doug Hart Another possible source of magnesium flares is to contact a fireworks manufacturing or aerial display group. If they can not provide the flares and the expertise of how to remotely light them, I'll bet they would know who to call. I found several fireworks manufacturers and aerial display companies with an internet search. Seems worth a try. And by the way, I'm pretty sure I am not the only one here that wants to hear how this one turns out! Besides the difficulty of lighting the shot, I want to know how you are going to protect the camera from the thousands of tons of building that are going to fall on it. Bill Bennett One of the leading manufacturers of distress flares is Pains Wessex in UK at the following site www.painswessex.com/ After speaking with them I'm too sure that they are an option for my demolition shoot. They produce a lot of smoke and they burn at 2000 Centigrade. How will we protect the camera? Basically, there will be a precision built steel case around each camera made of 1/2 inch steel. This will be lined with 1 inch of very high density foam, (not much foam I know but the Stalex cameras can take 100gs whilst shooting) This will form the "new" body of the camera.
For instance, the cameras on the ground floor will have to withstand the impact of the weight of the falling concrete, followed by the build up of pressure caused by the weight of the 20 floors above "settling" onto the debris pile. We can calculate the pressure with some basic arithmetic. If the building weight is about 150,000 tons and the debris pile has a footprint of about 100 square feet then on average the weight on any one square foot is 15 tons. To accommodate this the cameras on the ground floor will either have another steel box around them, or an arrangement of concrete slabs forming a cubby hole or both! We will also weaken the floor to create a survival space underneath the camera. The outer case will be about about 30 x 30 x 30 inches and constructed of 1 inch thick flame cut steel plate. This box will take a direct hit from the pointed end a 500 kilo concrete slab, traveling at 40 mph. At least that's what my engineer says.... The cameras that are on the roof, traveling down with the building need to be cushioned from their impact, of 32 mph, with the debris pile. They will be housed in one of the 1/2 inch thick steel boxes lined with foam. On the outside of this box we will secure a energy absorbing material that is lightweight and cheap. Materials that we have been investigating are aluminum honeycomb, as used in the auto industry (expensive), air tight plastic bottles, as used by paragliders (effective but bulky), rubber tyres (springy- the camera may end up 2 blocks away!), high density foam, formed into wire mesh box (effective but expensive). The last/first time I did this shot the video equipment was little damaged and we constructed the box without any impact absorbing material on the outside. The box ended up on the top of the debris pile, so we just walked up and hauled it away! I hope we have as much luck on this shoot This weeks "in" list This weeks "out" list Mike Brennan
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