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Author Topic: How to reduce beam angle on washes  (Read 5812 times)

Scott Hofmann

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Re: How to reduce beam angle on washes
« Reply #10 on: February 29, 2016, 10:55:09 pm »

No they don't.  They do both.  It is a holographic material.  There is one that narrows. 

Again I'll refer to the adj dotz product that is 80 degree without the lens and 10 or 20 with it.


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I think you will find that Elation's LSF product widens the beam angle per Elation's statement: "Effective Angular Output˜ (light source angle)? + (LSF angle)?", although their formula is a little off in that it is not simple addition. I will agree that the 1 degree x 60 degree LSF is a different case since it must both widen the beam in one direction and reduce it in the other. Not saying all holographic lenses MUST widen, but all the Elation ones do except 1x60.
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James Feenstra

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Re: How to reduce beam angle on washes
« Reply #11 on: March 01, 2016, 01:40:17 pm »

I think you will find that Elation's LSF product widens the beam angle per Elation's statement: "Effective Angular Output˜ (light source angle)? + (LSF angle)?", although their formula is a little off in that it is not simple addition. I will agree that the 1 degree x 60 degree LSF is a different case since it must both widen the beam in one direction and reduce it in the other. Not saying all holographic lenses MUST widen, but all the Elation ones do except 1x60.
actually the 1x60 still does widen both directions, as it would require a negative value to reduce beam angle as per their calculations

using elations calculation starting with a 10 degree light, it would be;
10 degrees (LSA) + 1 degree (LSF) = 11 degrees on axis X
and
10 degrees (LSA) + 60 degrees (LSF) = 70 degrees on axis Y

therefore widening both axis of light. You would require a negative LSF in order to reduce the beam angle on one of the axis.

You would need to relens the fixture (which is what you do with the aforementioned dotz par, fixtures like ETC's source 4 line and any projector with lenses) in order to reduce the beam size without loosing intensity for any significant reduction in beam size

top hats are generally used to reduce flare, and in doing so will generally narrow the beam slighting

egg crates are the other option, and can in some cases greatly reduce beam angle, but they're difficult to find for small fixtures, and your options are generally limited. They're more of a film/studio/photography lighting trick than an entertainment one.
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Elevation Audiovisual
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Jay Barracato

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Re: How to reduce beam angle on washes
« Reply #12 on: March 01, 2016, 03:27:52 pm »

Since we are talking about washes isn't the classic answer a fresnel lense?

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Jay Barracato

James Feenstra

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Re: How to reduce beam angle on washes
« Reply #13 on: March 01, 2016, 06:29:45 pm »

Since we are talking about washes isn't the classic answer a fresnel lense?
a fresnel lens doesn't inherently change the beam angle. the science behind the fresnel lens simply makes for an even dispersal of light across the field

the distance of the light source to the lens, as well as the size of the lens itself, dictates how wide or narrow the beam is
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Jay Barracato

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Re: How to reduce beam angle on washes
« Reply #14 on: March 02, 2016, 10:56:23 am »

a fresnel lens doesn't inherently change the beam angle. the science behind the fresnel lens simply makes for an even dispersal of light across the field

the distance of the light source to the lens, as well as the size of the lens itself, dictates how wide or narrow the beam is

Notice I used lense, as I was referring to the whole device, as opposed to lens. A lense includes the attributes in your second sentence such as distance from the source, I.e. the length of the lense.

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Jay Barracato

James Feenstra

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Re: How to reduce beam angle on washes
« Reply #15 on: March 02, 2016, 10:04:57 pm »

Notice I used lense, as I was referring to the whole device, as opposed to lens. A lense includes the attributes in your second sentence such as distance from the source, I.e. the length of the lense.
lense is the incorrect spelling of lens

http://www.english-for-students.com/Lense-and-Lens.html

they are the same device, and refer entirely to the piece of glass that focuses light only.

I think you mean a lens assembly...which would be something like a series of lenses at fixed (or adjustible, ie. a zoom lens) distances to achieve a certain result
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Jay Barracato

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Re: How to reduce beam angle on washes
« Reply #16 on: March 03, 2016, 05:28:12 pm »

lense is the incorrect spelling of lens

http://www.english-for-students.com/Lense-and-Lens.html

they are the same device, and refer entirely to the piece of glass that focuses light only.

I think you mean a lens assembly...which would be something like a series of lenses at fixed (or adjustible, ie. a zoom lens) distances to achieve a certain result

WTF

I mean a lens assembly. Now I agree with half of the sources, but the other half agree with my original use. Oxford dictionary agrees with you, Webster's agrees with me, Canon agrees with you, Nikon agrees with me.

The site you cited ( and why would that be authoritative) isn't even referring to the whole assembly.

Why bother being so pedantic, everyone who has studied physics knows the focal point depends on the distance from the source to the lens.

My point was that a fresnel lens in a proper assembly gathers the light behind it and changes the focus, which includes the beam width.

And yes they can narrow the beam, that was the point of using them in lighthouses to begin with.

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Jay Barracato

frank kayser

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Re: How to reduce beam angle on washes
« Reply #17 on: March 22, 2016, 11:40:49 am »

A fresnel lens is basically a segmented, flatter version of a lens with spherical surfaces.  Not good to pass clean, undistorted images (as in a camera lens*) but used in many situations to control the beam pattern of light, usually of a point-source light. Used in everything from lighthouses to headlights to stage fixtures, to those thin plastic sheets to enlarge print in a book. Fresnel lenses provide a lightweight alternative to solid glass versions of the lens which would be heavy, expensive, and in the case of a 360 degree lighthouse lens, physically impossible to construct.


As it is "just" a lens, depending on the effective curvature of the front and rear "lens" surface, it can either narrow or spread the light beam.  Seems mostly in PAR fixtures, the lens will narrow the beam, and the amount can be variable if the fixture has a lens position adjustment.


They are not effective generally on LED fixtures where there are many points of light - Assume, if you will, a three LED light - if each had its own lens, with each LED at the focal point of the lens, that lens array could be used to control the pattern.  On a fixture with, say, 108 10mm LEDS, one would need 108 tiny lenses to effect the same result.  And if you look carefully at the end of a typical projector-type LED, you will see just such a lens cast into the plastic. Of course, the design of that lens is what will give it its coverage pattern.


This is why normal tungsten pattern control devices don't work well at all with LED lamps - unless it is a high power, single LED source.


frank


* Canon has their DO series of lenses - diffractive optics - that are in principle fresnel lenses, but with a very high degree of accuracy as to not distort or cause unwanted artifacts in the resultant images.
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Rick Powell

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Re: How to reduce beam angle on washes
« Reply #18 on: March 25, 2016, 09:28:30 pm »

I have quite a few Blizzard Q12A washes that I use to light up the stage.  I use complementary colors, but still, colors wash together thus ending up in some off-white blend when the beam reaches the stage.  I'm thinking that a narrower beam angle on the washes would create more discernible color at the stage.  Are there beam "focusers" you can get for LED washes what would narrow the beam more?

I don't think anything will be too effective turning a Q12A into a spot. There are relatively few LED spot fixtures that are any good that aren't movers. Blizzard used to make a COB unit called a Raygun but I think they've discontinued it. I have 8 of the generic versions of the Blizzard Rokspot and they work beautifully, if underpowered at 15 watts.  A 50 watt version of these (which I think the Raygun was) would be dynamite.
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Jerome Malsack

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Re: How to reduce beam angle on washes
« Reply #19 on: March 28, 2016, 07:57:16 pm »

In theater it would be a Source 4 leko.  This light allows for focus and image gobo, and Color Gels.  The newest is available with LED and DMX built in.
Price wise not in the same market as the Blizzard  and Par 64  led  systems. 

Even the new LED small Follow Spots are to large for the bar stages.  I use one for some theater like work at church and children shows.  Maybe a wedding.
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ProSoundWeb Community

Re: How to reduce beam angle on washes
« Reply #19 on: March 28, 2016, 07:57:16 pm »


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