Question Concerning HMI's

[jambredz]

i'm planning my next possible music video and i want to use hmi's but not sure the wattage i need. These will be used for back lighting the subject and also rain and i will bounce that back into the subjects face. I need these HMI's to be able to throw this light a maybe 15-20 ft (not sure as yet.) shooting in the daylight so reflectors will be used to also harness the sun. the hmi's are primarily to backlight the "rain" and artists. I've never worked with HMI's before so i'm trying to see what power hmi i'd need and also try to understanf the HMI watts.
A 1.2 par is equivalent to what in tungsten?
4k par is what tungsten equivalent? how do you work it out? does it work out to be 3-4 times as with florescent? So 1.2k is roughly 4k tungsten?

Also do you think 1.2 is enough to do the job. I know its a pretty vague question but i'd like some idea of what 1.2k can do out in the sun.

Also you guys have any links to vids of rain in the day being backlit?

 

[Eileen Ryan]

A 1.2 par is equivalent to what in tungsten?
4k par is what tungsten equivalent? how do you work it out? ....
Also do you think 1.2 is enough to do the job. I know its a pretty vague question but i'd like some idea of what 1.2k can do out in the sun.

I assume you are generating the rain if you plan to also use reflector boards to bounce sunlight. You are going to need at least a 4k to backlight rain so that it will read on camera. Here are the HMI/Quartz equivalents.

An Arri 1.2k Par Plus with Wide Flood Lens has a Beam Angle of 58 degrees and puts out 204 Foot Candles at 20'. An Arri Baby 5k Fresnel in Flood has a Beam Angle of 52 degrees and puts out 221 Foot Candles at 20'. So the Arri 1.2k Par Plus puts out about as much as a 5k Quartz Fresnel.

An Arri 4k Par with Super Wide Flood Lens has a Beam Angle of 53 degrees and puts out 160 Foot Candles at 40'. An Arri T12 12000W Quartz Fresnel in Flood has a Beam Angle of 55 degrees and puts out 121 Foot Candles at 40'. So the Arri 4k Par puts out about as much as a Arri T12 12000W Quartz Fresnel.

The way to figure out the rough equivalency between HMIs and Quartz lights is to use the Arri Photmetric calculator on their website.

What light you will be able to use will depend on where your power is coming from. You can plug a 1.2 Par into a wall. You will need a generator or tie-in to power the 4k. Where are you shooting? Where is your power coming from?

Eileen Ryan, Gaffer

 

[slondon]

i'm planning my next possible music video and i want to use hmi's but not sure the wattage i need. These will be used for back lighting the subject and also rain and i will bounce that back into the subjects face. I need these HMI's to be able to throw this light a maybe 15-20 ft (not sure as yet.) shooting in the daylight so reflectors will be used to also harness the sun. the hmi's are primarily to backlight the "rain" and artists. I've never worked with HMI's before so i'm trying to see what power hmi i'd need and also try to understanf the HMI watts.
A 1.2 par is equivalent to what in tungsten?
4k par is what tungsten equivalent? how do you work it out? does it work out to be 3-4 times as with florescent? So 1.2k is roughly 4k tungsten?

Also do you think 1.2 is enough to do the job. I know its a pretty vague question but i'd like some idea of what 1.2k can do out in the sun.

Also you guys have any links to vids of rain in the day being backlit?

Also do you think 1.2 is enough to do the job. I know its a pretty vague question but i'd like some idea of what 1.2k can do out in the sun.

Also you guys have any links to vids of rain in the day being backlit?

Have you considered doing it all with the sun? Depending on the location and how long the shoot is you might be able to get by nicely without any artificial lights. The drill is to put the sun behind the artists for edge light and to backlight the rain and use bounce for key and fill.

 

[jambredz]

thanks guys...really helpful info. Yes Eileen i'd be using a generator. The size of which i havent determined as yet. But its supposed to be a junkyard/ mechanic place with cars and guys working on them. And yes i'll be generating the rain.

Slondon i have used back light from reflectors from the sun to back light people and it looks really nice...however to back light rain...i need much more direct punch if you get me.

 

[RyanT]

thanks guys...really helpful info. Yes Eileen i'd be using a generator. The size of which i havent determined as yet. But its supposed to be a junkyard/ mechanic place with cars and guys working on them. And yes i'll be generating the rain.

Slondon i have used back light from reflectors from the sun to back light people and it looks really nice...however to back light rain...i need much more direct punch if you get me.

I think he's saying to stage it so the sun is your backlight, then use your reflectors or the 1.2 to fill.

 

[jambredz]

would that work? I'm thinking the angle of the sun wont be ideal. wouldn't it be better to have the light coming from a lower angle and more direct? I will test to see if i can backlight with the sun with my hose

 

[Barry_Green]

would that work? I'm thinking the angle of the sun wont be ideal. wouldn't it be better to have the light coming from a lower angle and more direct? I will test to see if i can backlight with the sun with my hose

It'll work, but not for that long, because the sun moves so fast. If it's a short shoot, that's the way to go, you just have to plan the shoot time based on what your background needs to be, and when the sun will be in the right place for that background. If it's an all-day shoot, needing a consistent background, then no it won't work and you'll need to have lighting instruments on hand.

 

[jambredz]

kool kool. thanks peeps.

 

[slondon]

thanks guys...really helpful info. Yes Eileen i'd be using a generator. The size of which i havent determined as yet. But its supposed to be a junkyard/ mechanic place with cars and guys working on them. And yes i'll be generating the rain.

Slondon i have used back light from reflectors from the sun to back light people and it looks really nice...however to back light rain...i need much more direct punch if you get me.

I meant putting the sun behind the talent and using it to backlight the rain and the artists. Then bouncing it for key and fill.

I suggest that because it is so common here not to have very big budgets for fixtures, and in your case, probably, a tow generator too, if you decide you need HMIs bigger than 1200W, which are pretty puny compared to the sun. The disadvantage of the sun is that it moves but if you shoot your wide and medium shots pretty quickly you can probably cheat the talent's positions on the CUs so that you can't tell a few hours have passed. Only you can evaluate that.

It sounds like you want the sun somewhere in front of the talent. That's bad news aesthetically unless you really want hard shadows and for the talent because it makes them squint. That's overcome by flying an overhead of some kind. Lots of people like poly silk but I prefer Hampshire or half Hampshire frost, vinyl, because it softens the shadows while making less than a stop's difference between under the rag and the background. You'll need at least a 12'X12' overhead or possibly a 20' square and the frame and big roller stands to go with them, to say nothing of the many hazards from wind, which always seems to show up out of still air the minute you break out one of these things.

You probably have the luxury of testing anything that doesn't involve the HMIs so do it.

 

[nejuicer]

i'd be using a generator. The size of which i havent determined as yet. But its supposed to be a junkyard/ mechanic place with cars and guys working on them. And yes i'll be generating the rain.

If you are going to be creating rain, you should use GFCIs on all the cables supplying your lights – whatever size they happen to be. GFCIs are a must when working around water in order to avoid someone taking a potentially lethal shock. If you stick with smaller quartz lights, you will be fine with the hardware store variety of GFCI cords. But, if you use HMIs, or even Kinos, you will need film style GFCIs, like Shock Blocks, that are specifically designed for motion picture lights. To prevent the nuisance tripping that electronic Kino & HMI ballasts can cause with standard GFCIs, film style GFCIs sense on an "Inverse Time Curve." And, to deal with the harmonics that non-PFC Kino & HMI ballasts kick back into the power stream (that will cause other GFCIs to trip), film style GFCIs include a harmonic filter with a frequency response up to 120 hz. 3rd harmonics are attenuated by 50%, and by 500 Hz are down to 20%. Attenuated by the filter, the harmonics generated by dirty loads such as non-PFC Kino & HMI ballasts, pose less of a problem.

A single 100A GFCI "Shock Block" can provide ground fault protection on wet locations for the entire distro system of a Honda 6500 portable generator when used in-line with a Step-Down Transformer/Distro. ​

One problem with Shock Blocks is that they don’t come smaller than 100Amps. If you can’t rent a tow generator with a distro box with 100A pockets, the next best thing is a step-down transformer like the 60A Full Power Transformer/Distro we make for our modified 7500W Honda EU6500is generator. A transformer will step down the 240V output of a portable gas generator to a single 60A 120V circuit that you can put a Shock Block on.

A 100A GFCI used inline with a transformer can provide safe and secure ground fault protection for an entire distribution system consisting of Bates Extensions, Splitters, and Break-Outs to Edisons – eliminating the need for hardware store 20A GFCIs that are not designed to be used with harmonic generating loads like non-PFC HMI & Kino Ballast, & LED Power Supplies. Used in-line with transformer/, a 100A Shock Block will provide a larger GFCI protected circuit than is commonly available in homes. In fact, it enables the operation of even 4k HMIs on portable generators with GFCI protection.

If you are working in a garage, you may not need a generator at all to power larger HMIs like 4ks.
The same transformer that would step down the 240V output from a generator will work on a 240V circuit in the garage wired for a compressor.

Master shot of an iRobot commercial lit with a 4kw HMI Par (outside) & 1.8kw HMI Par (inside) powered from a 30A/240V dryer outlet through a step-down transformer/distro. Note: Sunny feel created by 4k Par on an overcast day. [/CENTER]

I used this approach on a recent commercial for iRobot (see production stills attached.) The spot contrasted the iRobot Scooba designed to clean kitchen floors to the old mop and bucket approach. For the mop and bucket approach we had a haggard looking Mom slopping water all over the kitchen floor as kids ran slipping and sliding across the floor.

Left: Transformer/Distro plugged into a 30A/240V dryer outlet. Right: 4K HMI Par under rain protection powered by Transformer/Distro [/CENTER]

Because we knew water would get everywhere we used one of our 60A Transformer Distros on a Dryer Plug to power a 4K HMI, a 1800W HMI, and some Kinos. We put a 100A Shock Block like the one pictured above on the load side of the transformer/distro to provide Ground Fault protection inside around the wet kitchen floor. It was a good thing that we did, because it ended up pouring rain that day and so the Shock Block did double duty for the 4k that was outside the kitchen window.

Left: Arri AS18 1800W Par powered from Transformer/Distro. Right: 4Kw and 1800W HMI ballasts powered from Transformer/Distro. [/CENTER]

For more detailed information on using Shock Blocks to provide Ground Fault protection on Dryer/Range plugs or with portable Honda generators, I would suggest you read the article I wrote for our company newsletter on the use of portable generators in motion picture lighting.

This article is cited in the just released 4th Edition of Harry Box's "Set Lighting Technician's Handbook" and featured on the companion website "Box Book Extras." Of the article Harry Box exclaims:

"Great work!... this is the kind of thing I think very few technician's ever get to see, and as a result many people have absolutely no idea why things stop working."

"Following the prescriptions contained in this article enables the operation of bigger lights, or more smaller lights, on portable generators than has ever been possible before."​

The article is available online at http://www.screenlightandgrip.com/html/emailnewsletter_generators.html.

Guy Holt, Gaffer, ScreenLight & Grip, Lightng & Grip Rental in Boston

 

[jambredz]

thanks Slondon. very good info.

Nah i hate having the sun straight on...i luv using it as a backlight and bouncing like in the face and filling it out. Just thought it may not show up the water droplets as clearly...and yes the sun moves fast. I'll go test what i can. Thanks again!

 

[jambredz]

whoa....Guy....dang. Thanks for all that info. You guys rock.