Should I buy a 5000k Arri tungsten or 2.5k HMI?

G

Gregg

Well-known member
I rented a 2.5k HIM this week and the rental guys said the best thing would just to get a 5k tungsted and gel it for daylight. He said then it would give the same light as a 2.5k HMI for much less money.

Other than the extra heat the light puts off are there any other disadvantages/advantages?
 
No way. If my brain serves me right... a full CTB to get tungsten daylight balanced, will lose you two stops, making that 5K the equivalent of a 1250w light. On top of that HMI's are more efficient than tungsten (2 or 3 times as bright per-watt? someone correct me on that?), so the light output between those two scenarios is no contest-- the HMI is way brighter in this case.
 
hemophilia said:
No way. If my brain serves me right... a full CTB to get tungsten daylight balanced, will lose you two stops, making that 5K the equivalent of a 1250w light. On top of that HMI's are more efficient than tungsten (2 or 3 times as bright per-watt? someone correct me on that?), so the light output between those two scenarios is no contest-- the HMI is way brighter in this case.
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That's right about 85 to 108 lumens per watt. 3 to 4 time is a good rule of thumb. Metal halide, another technology, is listed at about 80 to 140 lumens per watt so even a bit more efficient. Personally I wouldn't be investing in any more high wattage tungsten lights. Especially if you'll be using it at your home. You'll have to put in a special circuit for a light like that one.
 
The "guy" at the rental house must have been high! A 5k tungsten with full CTB isn't even remotely close to a 2.5k HMI. Even a 10k wouldn't match, it would take close to a 25k to equal the HMI.

Here is the data:

Consider a 2.5k HMI (like a Mole 6641 Daylite Par) with a medium lens. At a distance of 20' this will produce a 10.34' diameter circle of light with an intensity of 2406.25 FC.

Now compare this to a 10k Fresnel (like a Mole Tener Solar Spot). Set to full flood at a distance of 20' this will produce a 12.3' diameter circle of light with an intensity of 1040 FC. If you add full CTB (Lee 201 as an example) this will have a light loss of 1 2/3 stops (or 3.182:1). This reduces the output of the 10k to 326.8 FC under these conditions.

So a 10k tungsten would be less than 1/7th the output of a 2.K HIM, a 5K tungsten would be about 1/15th of the light output.
 
khmuse said:
The "guy" at the rental house must have been high! A 5k tungsten with full CTB isn't even remotely close to a 2.5k HMI. Even a 10k wouldn't match, it would take close to a 25k to equal the HMI.

Here is the data:

Consider a 2.5k HMI (like a Mole 6641 Daylite Par) with a medium lens. At a distance of 20' this will produce a 10.34' diameter circle of light with an intensity of 2406.25 FC.

Now compare this to a 10k Fresnel (like a Mole Tener Solar Spot). Set to full flood at a distance of 20' this will produce a 12.3' diameter circle of light with an intensity of 1040 FC. If you add full CTB (Lee 201 as an example) this will have a light loss of 1 2/3 stops (or 3.182:1). This reduces the output of the 10k to 326.8 FC under these conditions.

So a 10k tungsten would be less than 1/7th the output of a 2.K HIM, a 5K tungsten would be about 1/15th of the light output.
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Do you prefer a fresnel or using individual lenses like on the Mole?
 
eureka said:
get the dedolight 400D HMI
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How could that possibly put out as much light as a 2.5k Arri?

I need to light up a group of 4 people so need fairly large coverage. As I understand the Dedos are great at putting out very tight and powerful beams.
 
Gregg said:
Do you prefer a fresnel or using individual lenses like on the Mole?
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A Daylite Par like the Mole 6641 can be equipped with either a 2.5 or 4K globe. Its list is $5995. With a 2.5k globe lensed for a 10.34' diameter beam it will achieve 2406.25 FC of illumination.

A Solarspot (Fresnel) like the Mole 6341 can only use the 2.5k globe. Its list is $4250. With a 11.6' diameter beam it will achieve 1600 FC of illumination.

The advantages of the Fresnel are somewhat lower initial cost, a greater range of control compared to individual lenses.

The advantages of the Par are higher output for the same power input and the ability to use a larger globe.

Either is an excellent source and will serve you well in many different applications.
 
If you were considering using a 5k Tungstun, you could also just use a 1.2k HMI. Are you looking to buy or rent? If you are looking to buy I am going to be selling 3 1.2k Arri Daylight Fresnel Kits with FF electronic ballasts for $2k each in about a week. PM me if interested.
 
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