1200 watt bulb in arri 575 fixture?

C.J. Scheppers · May 18, 2009

Hi, can I use a 1200 watt bulb in an Arri 575 watt HMI fresnel fixture with the proper 1200 watt ballast? Is there anything different about the igniter? Thanks!

Matthew Parnell · May 20, 2009

No, no, no, no and especially NO!

It is never a good idea to overrate lamps at the best of times, with HMI's this can turn deadly. Unless you are an engineer and can safely convert the head to 1200w and have insurance to do so DON'T DO IT!

JD Hartman · May 20, 2009

It would require a little more research, but I'm fairly sure the igniter in a 575w head would not be able to strike a 1.2 HMI globe. There are replacement HMI igniters that are adjustable. You probably would also have focus problems plus additional heat issues. Why would you want to do this?

I don't think the resulting light output would be "pleasing", for the same reason that output from 10" 1k fresnel is bettter than that of a 7" 1k.

Karel Bata · May 20, 2009

plus additional heat issues.

Big time! A lot of a lamp's design is about dissipating heat - look at how quickly a lamp blows when some idiot rigs it upside-sown. A head is built to the minimum size practicable for the intended bulb.

Matthew Parnell · May 20, 2009

It is really not worth the risk... is saving a few grand worth endangering lives?

Chris Keth · May 20, 2009

It would require a little more research, but I'm fairly sure the igniter in a 575w head would not be able to strike a 1.2 HMI globe. There are replacement HMI igniters that are adjustable. You probably would also have focus problems plus additional heat issues. Why would you want to do this?
I don't think the resulting light output would be "pleasing", for the same reason that output from 10" 1k fresnel is bettter than that of a 7" 1k.

Not to undermine all of the safety concerns (all of which are valid) but many 575 ballasts are really 575/1200 ballasts and will work for both fixtures so that part would be taken care of if one wanted to pursue this (safely, please).

Richard Andrewski · May 21, 2009

Not to undermine all of the safety concerns (all of which are valid) but many 575 ballasts are really 575/1200 ballasts and will work for both fixtures so that part would be taken care of if one wanted to pursue this (safely, please).

Actually, the ignitor is the same in some 575w and 1200w models. The main difference will be in the voltage/current sent by the ballast which may in fact turn out to be a dual ballast that can do either 575 or 1200. The way such a ballast knows whether its a 575 or 1200 bulb is usually by the wiring configuration from the head to the ballast. There will be some jumper inside one or the other which shorts two wires together like a switch, and this informs the ballast which head it is: 575 or 1200.

Ignoring whether you can do it or not, the practical matter is that the sockets are probably completely different from a 575 or 1200 model. G22 for hot restrike 575 and G38 for hot restrike 1200 if you're talking single ended which is very common these days. So you'd have to change out the socket.

If you did end up making it work, it'd be dangerous to say the least if you didn't get the wiring right from head to ballast. Have to be sure your model is capable of driving either 575 or 1200 and also that you know the way the wiring should work and whether the ignitor in your fixture is in fact a dual 575/1200 type.

Something would blow for sure if you get any of these various points wrong. So, best not to experiment with it.

Karel Bata · May 21, 2009

And no way would insurance cover you for a mod like that. You might even find electricians refusing to touch it, and producers getting annoyed with you for creating a problem.

Your lamp life would be a fraction of what it should be. Temperature is a major factor in lamp performance. I haven't the figures for HMIs but I know that if you run tungsten lamps at 90% Voltage, you will increase their life by a factor of 10! - though I simplify, and there are other issues involved with the physics of a quartz envelope

This is because at a lower voltage the filament is not glowing at the full 3200Kelvin. All filaments slowly (and to put it simply) evaporate until there is a portion that is so thin it can't handle the current and it blows. It's why lamps of different ages can show subtle differences in color. Hence, running at a lower temperature the lamp lasts longer. Theatre lamps (where color temp is not such an issue) do a neat trick and burn at 3000Kelvin and consequently their lamp life is substantially longer - by at least a factor of 4.

The base lamp temperature of an HMI should not exceed 250C (280 in the case of an 18K, but that has a fan and foamed aluminium heat sinks!). In a lamp housing designed for a 575, a 1200 will get a lot hotter than it should be and will burn out very quickly. Color temperature will decrease too, and you'll likely get flicker.

The igniter for a 575 may well 'work' for a 1200, but I doubt it's optimal. As electrodes erode they need more voltage to create the initial spark, so you may find that after 100-200 hours it will lack the required 'oomph!' to get the bulb going, while the lamp itself is still servicable.

And Richard, have you heard of this thing about how a new HMI lamp will have an excess of UV? I've heard it's wise to put on a UV filter on the camera lens, but I've never seen (well, noticed) anyone do it...

Richard Andrewski · May 22, 2009

The igniter for a 575 may well 'work' for a 1200, but I doubt it's optimal. As electrodes erode they need more voltage to create the initial spark, so you may find that after 100-200 hours it will lack the required 'oomph!' to get the bulb going, while the lamp itself is still servicable.

And Richard, have you heard of this thing about how a new HMI lamp will have an excess of UV? I've heard it's wise to put on a UV filter on the camera lens, but I've never seen (well, noticed) anyone do it...

When the ignitor works for either a 575 or 1200w head, its because its rated for 1200w so its not a problem. Our units work like that and so do some Arri's.

On the UV output, yes there most definitely is a UV output which is different for different wattages and types of bulbs. Most fixture manufacturers build some kind of UV protection into the lens of the unit as you would have far worse problems with such an HMI than what it might be doing with the camera. Think sunburns...

I think if you aren't sure and want to be absolutely safe, you put some of the Lee Filters Tough UV protection on the light and then you're covered for sure.

Chris Keth · May 22, 2009

This seems as good a place for this question as any:

Why can 800 watt HMIs (jokers) be made in such a small package and you guys are worrying about making a 1200 in a 575 package? Isn't it comparable? I don't really know enough about the specifics of HMI fixtures to know if that's a dumb question or not, by the way.

C.J. Scheppers · May 22, 2009

Hi, thanks for all of the replies. When I posed the question, I thought the Arri 1200 watt fixture would be the same size as their 1000 watt tungsten fixture. Turns out that the Arri 575 HMI fixture is the same size as their 1000 watt tungsten fixture and the Arri 1200 HMI fixture is a size up from that, having a 6.9 inch lens and a 9 inch scrim/barn door assembly. Also looks like Arri makes a Studio series of fixtures which are one size up from the Compact Plus series. So I'll withdraw the question about running a 1200 watt HMI bulb in the 575 fixture.

Richard Andrewski · May 22, 2009

This seems as good a place for this question as any:

Why can 800 watt HMIs (jokers) be made in such a small package and you guys are worrying about making a 1200 in a 575 package? Isn't it comparable? I don't really know enough about the specifics of HMI fixtures to know if that's a dumb question or not, by the way.

You can make small fixtures with larger wattage HMIs but in general its not a good idea for bulb life. You can think of the fixture as a heat sink for the bulb. The more heat sink the more the life of the bulb. So you trade off portability and size for bulb life in general is another way to say it.

When you have a ballast that can drive a 575 or 1200w, its 99% the case that its two different heads you'll be driving (and not one that can do both) as its not very practical for reasons of the socket alone to do both in one head. As I said, there will usually be a subtle difference in the wiring of the cable between a 575 and the 575/1200 ballast and a 1200 and the 575/1200 ballast. This is the signal the ballast needs to know to be able to turn up or down its power to drive a 575 or 1200 bulb. Getting those signals crossed would be dangerous as we said before.

Doug Brantner · March 23, 2010

This seems as good a place for this question as any:

Why can 800 watt HMIs (jokers) be made in such a small package and you guys are worrying about making a 1200 in a 575 package? Isn't it comparable? I don't really know enough about the specifics of HMI fixtures to know if that's a dumb question or not, by the way.

Also, I've noticed that a Joker 800 gets much hotter (and takes a lot longer to cool down) than an Arri 1200.

Marc Galerne · March 24, 2010

Also, I've noticed that a Joker 800 gets much hotter (and takes a lot longer to cool down) than an Arri 1200.

As Richard mentionned:

" You can think of the fixture as a heat sink for the bulb. The more heat sink the more the life of the bulb."

If you look at a Joker Bug 800, it is 2 parts; the Bug part which holds the lamp socket and the Beamer which is the part holding the parabolic reflector. The Bug part is actually designed as a big heatsink and the Beamer is made of machined thick aluminum.

The reason it runs hotter is because it is actually doing its job of evacuating the heat generated by the bulb. It takes longer to cool down because it's solid thick aluminum but I am convinced the bulb will be cool sooner that in a conventionnal housing.

Marc Galerne · March 24, 2010

Also, I've noticed that a Joker 800 gets much hotter (and takes a lot longer to cool down) than an Arri 1200.

As Richard mentionned:

" You can think of the fixture as a heat sink for the bulb. The more heat sink the more the life of the bulb."

If you look at a Joker Bug 800, it is 2 parts; the Bug part which holds the lamp socket and the Beamer which is the part holding the parabolic reflector. The Bug part is actually designed as a big heatsink and the Beamer is made of machined thick aluminum.

The reason it runs hotter is because it is actually doing its job of evacuating the heat generated by the bulb. It takes longer to cool down because it's solid thick aluminum but I am convinced the bulb will be cool sooner that in a conventionnal housing.