Cheap Trick #2- Diffusing Spectral Lights

[Aten_Imago]

I'm a newbie so forgive me if you all knew this trick. Today I just discovered how to diffuse the nasty splotchiness that invariably results from Xenon, Krypton and other such incandescent bulbs.The blotchiness it seems is partially the result of shadows cast by the 'struts' supporting the actual filament inside the bulbs. I know there is an excellent company than manufactures lenses that diffuse the light as it exits the flashlight's head (Flashlightlens.com). However, In one of my sudden flashes of inspiration ( craziness?) it occured to me that my cuprit bulb (MAG 4D) is still emitting a blotchy beam and that some of the photons are 'absorbed' by lens diffusion as straight beams are refracted and then reflected back into the headbefore the successful photons are reflected off the reflector and emitted outside of the flashlight lens. So I frosted a bulb and Violla ! Smoooth beam and hotspot... with, get this...near ZERO light loss.Tomorrow I'll add some of my proprietary diffused glass up front for a smooth as Paté beam from my first ever MOD. My question to the experts on CPF.Do any of you have data that answers the question "Is a frosted bulb weaker and therefore have a shorter life span that a non-frosted one"? If so, I'd appreciate a reference. Oh! I almost forgot ... the product I used to frost the blub is called Armour Etch - 3oz for $6.00 at Pearl Arts & Crafts - made in NJ USA. CAUTION! This product requires special care in handling. Read the Instructions very carefully, wear rubber gloves, goggles and be near ventilation and running water when using this stuff.
Thanks!!! /ubbthreads/images/graemlins/smile.gif enjoying this light blaster now....

 

[Ginseng]

Hi,
You found a very nice treatment for artifacty bulbs. I have been using frosted bulbs since July of last year with no incident. They have been failing in the normal way; blown filaments. BTW, here's my account of how to do it along with some pictures. PaulW also did some lux measurements to try and quantify the effects of the etching. Note: high performance bulbs such as some of those from Carley and all of those from WelchAllyn use borosilicate or aluminosilicate glass and as a result are resistant to acid etching. The only way to treat them is media blasting or grinding with a sanding wheel and a Dremel.

Ginseng's Acid Etching Post

Wilkey

PS. Welcome to CPF and enjoy the ride!

 

[Aten_Imago]

Ginseng
Zounds! I knew I had done well in joining CPF and look, you people are living proof of the "great Minds Think Alike" or as Jung put it- "Collective Subconscious" paradigms! Now I'm running around my studio frosting everything that has to do with lights. I'm etching the HAG ( Heat Absorbing Glass) of a Video Camera ENG light in hope it will smooth that 50W spectral beam. Yahoo! God Bless America with all it's great inventions!!! /ubbthreads/images/graemlins/thumbsup.gif

 

[Doug Owen]

[ QUOTE ]
Aten_Imago said:
Ginseng
Zounds! I knew I had done well in joining CPF and look, you people are living proof of the "great Minds Think Alike" or as Jung put it- "Collective Subconscious" paradigms!

[/ QUOTE ]

FWIW, the Poles have a folk saying "Fools seldom differ", which also explains why we seem to come to the same conclusions.......

Doug Owen

 

[Ginseng]

I take no exception to that, Doug. I think fools are much more creative! /ubbthreads/images/graemlins/wink.gif

Wilkey

 

[IsaacHayes]

I was thinking about this today. If you can diffuse closest to the light emiting source, the less wasted scatter. Take a white sheet of paper and try it against a flashlight, the farther you move it away the more dim and scattered it gets. So it's best to diffuse the emiter, next the reflector, and last the lens.

I was thinking if you had a splotchy luxeon, make some sort of clear opaque cap for it, and use a smooth reflector. It would diffuse the irregularities, but the reflector would re-collect and align the photons for the same tight beam.

But if you used a diffusing lens, then it just scatters the light and you loose your beam shape/pattern/tightness. Best to diffuse first, and then focus later.

 

[Harrkev]

If you think like an engineer, then you know what a "link budget" is. A 1db loss is a 1db loss no matter where in the link it is.

 

[IsaacHayes]

true, you will still loose some efficeiny but the focus will still be tight if you "blur" it before the reflector.

 

[Aten_Imago]

"A 1db loss is a 1db loss no matter where in the link it is."
Harrkev ...
That's true when you're talking sound ( you're refering to audio levels right?) However, with light that is passing through an optical maze, it makes a BIG difference where the diffussion is occuring. Here the scenario: 1- Filament or Phospher glows 2- Glowing filament emits straight beams of light. 1.A-In cases where those beams meet no obstruction, then the subject receives 100% of the photons emitted from that POO ( Point Of Origin). However, here's what happens in an incandescent flashlight's head.1.B- a certain percentage of beams hit the struts supporting the filament and are absorbed or partially deflected by strut edges. Those that are absorbed cause a photon deficiency in a pattern identical to the shape of the struts ( hence..."batwings"). These defficiencies are called shadows in common parlance. The shadows are effectively projected ( enlarged ) onto the mirrored surface of the reflector and the enlarged defficiencies or shadows, then present themselves in gargantuan form on the subject. 1C- some light beams are reflected off the inner surface of the bulb casing but they must be rather few because the casing is so small and besides, they are likely to exit the bulb surface eventually. Most beams of photons will pass readily through the usually crystal clear glass bulb casings.This is no problem in the case of LED's since they are not constructed in a manner that causes shadows of filament struts or filaments themselves, to cast shadows. Now, if the OUTER surface of an incandescent bulb is slightly frosted, it can alleiviate splotchiness considerably at a much lesser loss of net output than if such diffusion is on the relector or the lens or both. The reason is that because the surface area that is theoretically absorbing or reflecting 'lost' photons is much smaller in the case of the bulb as compared to the much larger surface area of the reflector surface or the lens in front of it, it stands to reason therefore, that the greatest cost benefit can be realized by diffusion at the source point in the photon 'value chain'. 3- In addition, the farther that an obstruction is from the filament or spectral source, the more distinct and larger shall be the shadow that it casts on the subject and, as comrad CPF'r IsaacHayes so astutely pointed out, The more photons will be absorbed before they have a chance to reach thier target. To summarize: The ideal solution to light beam blothchiness would be to first diffuse the bulb casing or surround the emitter with a very fine diffusion layer, and then control the size of the hotspot in relation to the surrounding circle of light with a combination of the reflector's parabolic formula, reflective plating/stipling or faceting and then finally affect the blending of the hotspot into the surrounding circle of light with diffusion of the lens itself.My guess is that for the most even resultant beam ( and this is mostly true for incandescents) a finely frosted bulb relecting light from a stochastic reflector and then a modulation of direct beams through a lens lightly frosted in a gradation from center to perrimeter would yeild a fine compromise beam that would be the brightest that an even beam could be. I have too little experience with LED's to reflect on how this would apply - but hpefully, those that do will jump in and feedback to us...Whew! sorry for the long post