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Ceramic Discharge Metalhalide


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#1 Olivier Koos

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Posted 25 December 2009 - 09:15 PM

Hi there,

have a look at this; http://www.coollight...esnel-p-63.html I wondered if anybody have had some experiences with Ceramic Discharge Metalhalide in comparisement to HMI's ?

Thanks

Oli
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#2 Olivier Koos

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Posted 26 December 2009 - 05:22 AM

or Quartz Metal Halide
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#3 Olivier Koos

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Posted 28 December 2009 - 11:10 AM

anybody?
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#4 andrew dean

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Posted 30 December 2009 - 11:46 PM

anybody?


I own 4 of the cool lights 150w cdm fixtures as well as a 575w HMI. I would absolutely recommend the cool lights cdm to anyone on a tight enough budget to be asking about them. They are versatile little units that provide quite a kick for the money.

advantages:
ok, the huge advantage is obviously price. You can buy stacks of these for the price of a branded HMI fixture. The CDMs cost around the same as a redhead (800w open face) class fixture, by my tests output roughly the same light as a redhead gelled CTB and draw what, 1/7th the power? If you shoot daylight, or have a limited power supply, these are gems.

If you compare them to an equivalent HMI source... I guess the closest would be an arri 125w fresnel hmi. With bulb and ballast that would come out to be around $2800, roughly 6x as much as the cool lights. Without any question the arri is a better built fixture without some of the rough edges of the cool lights. If i were a rental company or ran shoots where i really beat the heck out of the gear, i'd absolutely pick the arri. As a low budget production truck, I'm happy to have 4 of the cdm plus some other fixtures for the same price.

Anybody that works with HMIs knows that you get a color shift over the life of the bulb. Newer bulbs are bluer and older bulbs warm up a bit. I've been on sets where a new bulb in an arri sun spit out 8000k (surprisingly blue) and had to be gelled warmer. What is curious with the CDM is that they came out of the box a little bit warm to start with, flagging as 5200k when testing using the white balance in an ex3 (granted, not the most precise test). I haven't put enough hours on the units to have noticed a change, so i'll be curious to see where it goes from there. On the other hand, replacement bulbs are what, $30? You can change them out 6x as often as an hmi bulb for $200 if the shift becomes an issue.

There are some quirks to the cool lights cdms. The casting is a lower quality than an arri, with the mold lines being visible and some casting "tangs" along the edges of the air vents. The rotation lock looks kinda odd and the baby mount is some kind of abs plastic which looks kinda flimsy (but has held up really well so far.) The bottom line for me is none of the shortcomings of the unit have proven to be anything other than cosmetic. It looks a little rough around the edges, but ultimately, who cares?

I have one beef with the light quality. I don't know if its the bulb or the fresnel lens, but there appears to me to be a small hot spot towards the middle of the light. I've only noticed it when shining a splash onto a wall - not when lighting a scene, but still. The oddest part is that the hot spot kinda looks to have a color shift... like its a bit aqua. Again, its never been a problem shooting a scene, but I was surprised to see it when i pointed it at a wall specifically to test the focal range.

The biggest shortcoming of the CDMs vs. hmi is the power. I mean, 150w, even as hmi is "nothing" in the film world - hardly any power at all. The 120 and 200w hmi are more sold as specialty application fixtures and not keys. In the video world, I have more and more people hiring my cdm 150s as keys.

So i only reply because nobody else has. I'm far from a lighting expert. I will say this: I've used my cool lights CDMs mixed with a cool lights 575 hmi, an arrisun 575w and arri 1.2k par on shoots with veteran DPs and grips and never heard anything negative about the mixing of the sources. In fact, the only thing usually said about the cdms is "they were HOW much??"

Personally? I'm happy and would buy them again.

hope that helps, and holler if i missed a point you wanted me to make.

cheers,
-andrew
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