I'm looking into adding another HMI with a bit more punch to my kit (currently a Profoto 1.2k HMI PAR) is my biggest unit, and I'm wondering if anyone can comment on how the Arri 1.8k Baby Max compares to something more traditional like the Arrisun 2.5k PAR?
I'm in 240v land so I can run either off household power sockets here, I'm very intrigued by how the Arrimax reflector in the 1.8k compares to the Parabolic reflector in the Arrisun though, I seem to remember some people posting that it actually offers greater output than the higher wattage 2.5k unit, however I can't seem to find those posts in a search.
A lot of people claim that the M18s can replace 4K PARs, but I disagree. However, I think it's pretty unanimous that they out-perform the 2.5k PARs, not only with output but also in terms of ergonomics. They are smaller and lighter, and there are no lenses to deal with. They also pack a lot tighter in a truck, with no lens case and with a significantly smaller ballast. Of course in America with a 120v system, the advantage of powering from a 20A house circuit is huge for smaller productions as well. The one redeeming feature of the Arrisun 2.5k PARs is that you can also bulb them at 4K. The 2.5k Fresnels will probably remain useful longer than the 2.5k PARs, especially as M40s replace the Arrisun 40/25s in rental houses.
Buying an expensive lamp in the "film industry" in australia is not a good investment.
Well I'd say that depends entirely on whether it makes you money or not.
For me, there's simply no other option than going the name brand route. Three times I've had producers rent 1.2k HMIs for me for outdoor/portable-generator shoots; all three times the heads and ballasts have turned out to be cheap Chinese clones, and all three times the clones have failed to strike from 2kw and 3kw portable generators. Rendering the lights useless, the rental costs spent on them worthless, and my lighting for those scenes violently compromised.
I've had success with those same cheap Chinese clones on mains power, but I don't always have access to mains power on location, and a light I can't power from portable generators isn't worth the space it takes up in the ute.
Three times I've had producers rent 1.2k HMIs for me for outdoor/portable-generator shoots; all three times the heads and ballasts have turned out to be cheap Chinese clones, and all three times the clones have failed to strike from 2kw and 3kw portable generators. ... I've had success with those same cheap Chinese clones on mains power, but I don't always have access to mains power on location, and a light I can't power from portable generators isn't worth the space it takes up in the ute.
The reason the cheap Chinese clones work on the grid and not on portable generators is that the ballasts are not Power Factor Corrected (PFC.) As such, they draw current in abrupt bursts that are rich in harmonics. On the high impedance of generators, the harmonic currents drawn by non-PFC ballasts can cause voltage waveform distortion that can trip the generator’s breakers. Depending on the size and design of the generator, it may have 5 to 100 times greater impedance than a power grid transformer. Consequently, harmonic generating loads which work fine on utility power, will react entirely different when powered by a generator.
In practice, when you plug a HMI light into a wall outlet you need not be concerned about current harmonic distortion producing voltage distortion. The impedance of the power source (the grid) is so low, the distortion of the original applied power waveform so small (less than 3%), and the power plant generating capacity so large by comparison to the load, that harmonic currents fed back to it will not effect the voltage at the load bus (as can be seen in the left hand oscilloscope shot below. )
Left: Grid Power w/ 1.2Kw Arri non-PFC Elec. Ballast. Right: Conventional Generator Power
w/ 1.2Kw Arri non-PFC Elec. Ballast.
As is evident in the right hand oscilloscope shot above, it is an all together different situation when plugging a 1200W HMI into a small portable generator. Given the comparatively large sub-transient impedance of conventional AVR portable gas generators, and the high THD value of their inherent power waveform (see no load waveforms below), you have a situation where even a small amount of harmonics being fed back into the power stream will result in a large amount of harmonic distortion in its’ voltage.
Left: Original Grid Waveform w/no load & low THD (>3%)
Right: Original conventional AVR Generator (Honda EX5500) waveform w/ no-load & high THD (@17%)
Making the matter worse is that, given the increasing prevalence of non-linear light sources, such as LEDs and Flos in production, it is likely that the percentage of the generator’s capacity taken up by non-linear loads will be very high given its small size relative to the size of HMIs typically used on these generators (575-2500 Watts.) Small portable conventional AVR generators present a perfect (electrical) storm where the return of any harmonic currents results in a very high degree of voltage distortion and tripping breakers.
I've had an Arri 575 HMI not strike on a gennie. Has anyone else had to jumpstart an HMI? Since all we had was Kinos at the time (no high watt lamps), I actually hauled an 1875w air conditioner out to the middle of the woods on a tractor to get the necessary juice flowing to strike. I was given that tip by a grip friend of mine, but I've never heard of having to do that before.
Really appreciate the detailed explanation Guy, thanks! It's always nice to understand the root cause of these issues (and know that I'm not mad in justifying the much higher expense of name-brand HMIs!)
I've had an Arri 575 HMI not strike on a gennie. Has anyone else had to jumpstart an HMI? Since all we had was Kinos at the time (no high watt lamps),
Most Kino Flos are not power factor corrected and, as demonstrated in the oscilloscope shots below, can be a source of considerable harmonic noise in a power stream. For example, the older style Kino Flo fixtures that use the T-12 tubes (the Single, Double, and 4 Bank Fixtures, the Wall-o-Lite, Flathead 80, and the Image 20, 40, & 80 fixtures) are not power factor corrected and draw such harmonically distorted current that when used in quantity, as in studio chroma key productions, they can constitute a serious problem. For this reason, Kino Flo cautions users, on their website: “Kino Flo ballasts are generally not power factor corrected. They will draw double the current on the neutral from what is being drawn on the two hot legs. On large installations it may be necessary to double your neutral run so as not to exceed your cable capacity.”(FAQ “Why is the neutral drawing more than the hot leg”.)
Left: Grid Power w/ Kino Flo Wall-o-Lite. Center: Conventional AVR Power w/ Kino Flo Wall-o-Lite. Right: Inverter Power w/ Kino Flo Wall-o-Lite.
The generation of harmonic currents by production equipment should be eliminated whenever possible, otherwise harmonic noise can build to a point where it will have an adverse effect upon other equipment, such as Will’s Arri 575 HMI, running on the same power. In fact, a viscous cycle can get started. The more harmonic orders that are generated, the more distorted the power supplied by the generator becomes. The more distorted the power waveform becomes the more harmonic currents are thrown back into the electrical distribution system, which in turn, creates additional voltage distortion. In this fashion, something akin to a feedback loop can get started. Very often, the operation of electrical equipment may seem normal, but under a certain combination of conditions, the impact of harmonics is enhanced with unpredictable results.
Harmonic distortion is becoming a more prevalent problem because some of the power generation equipment we use on set was not designed to deal with the abundance of non-linear loads like electronic HMI, Fluorescent, & LED ballasts in use today. Running incandescent lights on generators was never a problem because as purely resistive loads they didn’t create harmonic currents. The problem began with the increasing use of non-linear lighting loads, like electronic HMI and Fluorescent ballasts, that generate harmonic currents. The problem is being further compounded by the increasing prevalence on set of sophisticated electronic production equipment like computers, hard drives, and HD monitors which require clean stable power to operate, but are themselves sources of harmonic distortion. Where in the past, much attention was given to generator features such as automatic voltage regulation, speed regulation and AC Frequency; given the increasing prevalence of harmonic currents and the problems they cause, an increasingly more important feature today is the quality of the generated waveform.
Guy Holt, Gaffer, ScreenLight & Grip, Lighting Rental & Sales in Boston