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Fresnel output with lens removed?


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#1 Mark Kenfield

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Posted 15 March 2014 - 08:07 PM

Hi guys,

I don't have any fresnels handy to test this at the moment, so I'm wondering if anyone could comment on the output you get from fresnel fixtures (particularly HMIs) when you remove the lens?

I've heard of people doing this before, but never tried it myself.

Is the ouput comparable to the lensesless ouput you'd get from a par of equivalent wattage?

I'm trying to find ways to get higher ouput for bounced light.

Cheers,

Mark
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#2 timHealy

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Posted 15 March 2014 - 09:24 PM

Going out on a limb here but WTF? Are u crazy?

 

The lens in HMI's are safety glass for UV protection.

 

Do not use HMI's without the safety glass! No if's and's or but's. For the safety of actors and crew.

 

On tungsten lights you can take out all the glass you want.

 

Best

 

Tim


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#3 Mark Kenfield

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Posted 15 March 2014 - 10:41 PM

Do no HMI fresnels have UV protection at the bulb? My par has protection at the bulb rather than built in to the lenses.
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#4 Adrian Sierkowski

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Posted 16 March 2014 - 12:21 AM

As far as I know all Fresnel HMIs are not UV protected on the bulb as they are not designed to ever be bare-bulb. When in doubt, doun't take it out.


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#5 Mark Kenfield

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Posted 16 March 2014 - 12:33 AM

Well that puts paid to that idea.
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#6 andrew ward

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Posted 16 March 2014 - 05:45 AM

Yeah the fresnels uv treated not the bulb. A par should have a safety screen and a safety switch. And the lenses are uv treated as well.

Its pissweak usually, the reflectors not as good as a par. A par with no lens is a poormans mole beam. A fresnel without a lens is a disapointment.
The fresnel gives much higher output.

You could try a "condenser" like a sunray par has instead of barn doors. Like a snoot but it goes a little wider and is reflective, so some of the flooding light you lose at the lens is condensed into reflective beam.

But basically, always get a bigger lamp and cut back

You could go crazy and retrofit like a babymax relector into an hmi and get a safety screen, but just get a bigger lamp.

Or do a bit of "fla spot" and walk the whole deal in.

Or get a spottier/more reflective bounce.

I should stop pontificating. It makes me feel important.
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#7 andrew ward

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Posted 16 March 2014 - 05:47 AM

Oh and dont take the lens out of a tungsten lamp unless you want a face full of glass.

They used to open the door on a 10k to get puntiform shadows but that scares me.
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#8 Leonardo Brocato

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Posted 16 March 2014 - 07:16 AM

If you want a very very harsh light you could open the lens but......

a fresnel hmi uses the lens to stop uv so you can't open it it's not safe and also all hmi have a microswitch in the closing of the lens so with the lens open the circuit it's not close so no strike.
For Pars like arri sun the uv block it's a clear lens also for safety and if you remove it's not safe for eyes and without lens the beam it's ridicoulous and useless. If you need more power in bouncing use par not the fresnel (much more output) or maybe an open face. Arri makes the X series that is an open face lensess like a redhead with an hmi. 

I use to open the lens of the fresnels tungstens to have a very harsh shadow in some situations.

Sounds strange but for bouncing the best it's an hmi open face like arri X.

 

Leonardo Brocato
Gaffer Rome Italy 


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#9 timHealy

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Posted 17 March 2014 - 07:26 PM

Do no HMI fresnels have UV protection at the bulb? My par has protection at the bulb rather than built in to the lenses.

do you have one of those older 1200 watt him pars that had the bulb in a sealed beam glass housing similar to a par 64 bulb? that type may have had uv protection built in, but i don't think anyone makes that anymore. i haven't seen one in years.


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#10 Mark Kenfield

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Posted 17 March 2014 - 09:43 PM

do you have one of those older 1200 watt him pars that had the bulb in a sealed beam glass housing similar to a par 64 bulb? that type may have had uv protection built in, but i don't think anyone makes that anymore. i haven't seen one in years.


I've got an older Profoto 1200w fixture, it's a buglight style fixture like the Joker Bugs, so the bulb sits in a glass UV cover (and the par reflector slides over the top).
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#11 andrew ward

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Posted 19 March 2014 - 12:51 AM

Maybe the issue is your weird umbrella fetish. Get a proper bounce and youd get more out of the lamp.
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#12 Brian Drysdale

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Posted 19 March 2014 - 01:59 AM

If you just want to bounce light, open faced lights like Redheads are fine for that kind of work. You can easily rig an umbrella in front of them if you want to.  


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#13 Mark Kenfield

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Posted 19 March 2014 - 06:51 AM

Maybe the issue is your weird umbrella fetish. Get a proper bounce and youd get more out of the lamp.


Don't you talk smack about my umbrellas.
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#14 Edward Lawrence Conley III

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Posted 19 March 2014 - 10:16 AM

I've got an older Profoto 1200w fixture, it's a buglight style fixture like the Joker Bugs, so the bulb sits in a glass UV cover (and the par reflector slides over the top).

 

The Pro Daylight has the UV protection in the Pyrex that covers the HMI globe, which you just described. It also has a safety switch/pin that the Pyrex sits on so if you take off the Pyrex it shuts off the HMI.

 

Fresnel HMIs have the same safety device- open up the door holding the Fresnel lens and the head should shut off.


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