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Felix Winterbottom

Gaffer's help

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Hello,

 

Just curious if anyone is used to doing this?

 

The Dp has requested 5K Skypans. Not the Mole Richardson type... The old ones.

 

I know they don't have any protection over the bulb. So if the bulb does shatter it will fall straight on the actors. I know they're open sources so I figure the heat will flow as well as with anything.

 

The thing is he does want to hang a 4x4 Ali frame underneath it to soften it a bit. Is this enough protection?

 

What's you general thoughts about this? I'd use a spacelight normally but they're going high speed on camera.

 

The shoot is in a couple of days so I need to make a call on this.

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How else would you suggest making a top soft source for a highspeed shoot?

 

Let's say we were shooting 2000fps and needed a tungsten based 20x20 softbox.

 

What would you do?

 

A lot of folks would bounce 10ks or 20ks into fabric, or you could always hang and shoot those units down through fabric.

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You don't want to burn skypans face down. The 5k DPY globes are limited to a 45 degree from base down burn position. A 90 degree angle changes the cooling characteristics and could cause globe failure, so your concern is valid.

 

Alternative fixtures to be used could be Mole MaxiCoops with your choice of PAR 64 globes. As with any tungsten source at such a framerate you are going to be subject to flicker. The benefit of multi-circuit fixtures such as these is phasing the 3 available circuits each on their own phase. As I understand it, the major issue with tungsten fixtures smaller than 5k is the flicker as a result of the filament's decay time between AC cycles. Since the phases are all tapped 120 degrees out of phase from each other, this ensures that as one phase cycles out, another phase of bulbs takes its place. There is a thread on this technique here: http://www.cinematography.com/index.php?showtopic=54634&st=0&p=364461&hl=+high%20+speed%20+shooting&fromsearch=1entry364461

 

Alternatively, if you have a strong Best Boy Electric and/or generator operator, you can look into the use of rectified DC, which eliminates the cycling problem. There is article on this here: http://provideocoalition.com/index.php/aadams/story/1000fps_on_a_budget/P0/

 

Or if you go the HMI route, make sure you get ALF ballasts.

 

Good luck.

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Thankyou Ross for a response.

 

We don't have many Mole products here unfortunately. I'm familiar with the Toplight, can't remember who makes it but it's effectively the same head. I could just go Dino route then for the softbox theory since they use the same heads.

 

That first link doesn't work for me. But I presume you're just talking about balancing the phases? Ive done this in the past and still had flicker. So I'm nervous to go that route.

 

The AC to DC rectifier idea here with that much KW is always a problem to get off the ground. I ran into a similar problem when I had a job and wanted to use carbon arcs. Found the heads finally. But couldn't get the DC.

 

I'd consider HMI. Loads more money of course. But I can't burn the Arri HMIs down either for the Arri High Speed Ballasts. Are they compatible with the Alpha 18Ks?

 

It still throws the lighting budget up 10 fold.

 

Is it not even worth the risk with Skypans?

 

 

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Thankyou Ross for a response.

 

We don't have many Mole products here unfortunately. I'm familiar with the Toplight, can't remember who makes it but it's effectively the same head. I could just go Dino route then for the softbox theory since they use the same heads.

 

That first link doesn't work for me. But I presume you're just talking about balancing the phases? Ive done this in the past and still had flicker. So I'm nervous to go that route.

 

The AC to DC rectifier idea here with that much KW is always a problem to get off the ground. I ran into a similar problem when I had a job and wanted to use carbon arcs. Found the heads finally. But couldn't get the DC.

 

I'd consider HMI. Loads more money of course. But I can't burn the Arri HMIs down either for the Arri High Speed Ballasts. Are they compatible with the Alpha 18Ks?

 

It still throws the lighting budget up 10 fold.

 

Is it not even worth the risk with Skypans? Is it not the heat build up within the 5kw fresnel that causes the problem beyond the actual 45 degree tilt? Surely the bulb in an open fixture can handle it?

Edited by Felix Winterbottom

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Just trying to think outside the box here. But, what about using the 5Ks on stands, on the ground, aiming them toward the center of the room, where you can hang an array of mirrors from your studio grid to reflect the lights down into your diffusion frame. Block out any spill onto your subject.

 

Just thinking...

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I can see a few issues with that.

 

The new cost of all those mirrors and stands. Everything else stand the same. We're not losing anything.

 

Then the fact you'd need more heads because the light will technically be travelling twice the distance.

 

Third, would all require more space.

 

Gus... Can't face those heads straight down.

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I can see a few issues with that.

 

The new cost of all those mirrors and stands. Everything else stand the same. We're not losing anything.

 

Then the fact you'd need more heads because the light will technically be travelling twice the distance.

 

Third, would all require more space.

 

Gus... Can't face those heads straight down.

 

I assumed it'd be at a sharp angle into the rag - it'll wrap :)

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you could hang the skypan and hang a mirror directly next to it at a 45deg to project it downwards. I know Briese makes a 5k tungsten umbrella that might do the job. they make a downlight similar to a skypan but with a bulb designed to operate vertically but im not sure if they make a 5k version.

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