Dichroic Glass V.S. HMI for hair lights

[MagicCat]

I'm wondering if anyone has any in-depth experience using Dichroic 32-56k glass filters on tungsten Lighting, for indoor use. I need daylight balanced hair lights for an upcoming shoot. On paper, Renting out a 200 watt HMI seems to be overkill, at least as far as the budget is concerned because it looks like I could actually OWN some glass for about the same price, and accomplish the same goal. White Light on top of Head. Its pretty much that simple

Will the Dichroic Glass filters truly match up to the color of my Daylight kino's and HMI's?

I assume any glass filter will eat a little light, but, at the risk of a few stops, I'm thinking my money could be better spent buying and owning some glass, rather than renting HMI fixtures, for this purpose?

I have some other Dichroic glass filters I bought off Ebay for cheap, I think they were for some Moles or something. They are convex 10 inch lens's. I put one on a Lowel DP and although it seemed the center was the correct color, the edges of the spot were red. Im not sure what that was about. Maybe they are old?? None the less, they are unusable due to the reddish circle they throw on the fringes of the light. They did the same thing when put up to smaller Fresnel too. That is what prompted my inquiry here, I don't want to end up with the same problem if that reddish ring is inherent to Dichroic Glass.

Mucho Gratis in Advance!!

David Walker

I will use it on some smaller 300 watt fresnells that I have in my kit. They are older Bardwell-McAllisters, but Im quite fond of them. They have taken a real beating over the years and still work like the day they came off the shelf.

 

[kplo]

Magic Cat,
All dichroics will get redder with age, as the coating fades with heat. You might be better off using something like a 1/2 booster blue (Rosco) on your hairlight. Many shooters prefer the "slightly warmer than daylight" look on a backlight/hairlight. Also, you won't lose as much light that way..and:gel sheets are relatively cheap. You can cut 4 gel frame size filters for the 300w B&M from a sheet of 1/2 blue.
Hope this helps.
Ken
the Screen Skins guy

 

[MagicCat]

Magic Cat,
All dichroics will get redder with age, as the coating fades with heat. You might be better off using something like a 1/2 booster blue (Rosco) on your hairlight. Many shooters prefer the "slightly warmer than daylight" look on a backlight/hairlight. Also, you won't lose as much light that way..and:gel sheets are relatively cheap. You can cut 4 gel frame size filters for the 300w B&M from a sheet of 1/2 blue.
Hope this helps.
Ken
the Screen Skins guy

Thanks!!

Yes, that is generally what I have been doing all along. Especially on platinum blondes with no skin color, if you can keep most the 32k light off their skin, it really warms them up and gives the hair some warmth and glow.

Anyway, I had thought maybe glass would be a little more accurate and consistant. And maybe, I could even use a glassed 32k light for fill if it is THAT accurate. (at least until they start permanently throwing in the blue towell, per-se) Gells go bad pretty quick under high heat. 2 or 3 1-hour sessions in front of a 300 watt Fresnel and they are toast.

I don't live in an area where I can easily replace gells without using mail/ups/Fed-Ex or a half day adventure in driving, to get to/fro the nearest pro-shop (cleveland Ohio) Then again, they are not expensive so I guess I should just stock up. You are probably right, I could probably buy a lifetime supply of 1/2 and 1/4 blue plastic for the price of 1 3-inch hunk of melted sand. (they DO make nice coasters after they have been through the toaster )

To cure my curiosity, Do you find that a fresh hunk of glass matches most daylight kino's or HMI's??

Thanks man!!

 

[kplo]

Magic Cat,
Actually, even when new, the dichroics for my Mickey Moles (1000w open faced focussing units) were never really 5600k. I metered the color temperature once and it came up around 4800-5000k; easily visible as slighty red, especially on old reversal film stocks like 16mm Ektachrome Commercial and EF. The dichroic coatings on actual globes ("FAY lights") was a bit more consistant...by the time it got red, the lamp was at the end of it's life anyway. .
If you use your fresnel 300s with the dichroics as "daylight" fill lights, you will probably have to add a 1/2 booster blue to get it up to temperature.
Fortunately, HMIs and fluorescents just about eliminated the use of add on glass filters.

Rosco or Lee gels are pretty stable under heat...you should do better than a few 1 hour sessions. However, even if you get 10 hours from a 1/2 sheet that you clip to the doors, you're only lookin' at about 4 bucks.
Also, remember that you need to use a GOOD UV filter in front of HMIs at any distance or Fluoros used in close, as they emit a lot of UV light. Eye killers for you, you crew and talent! So there's that cost to consider (although we usually buy the UV in rolls for use in gel frames on large units).
Hope this helps.
Ken
the Screen Skins guy

 

[Bucknfl]

Dichorics are a pain in the ass but they don't cut the light output as much as full blue gell. Do a test and see what works the best. Of course HMI's are great but the con is the price.