# Axial and Radial l ERS



## Grog12 (Oct 11, 2010)

What is the difference between an Axial and Radial (or non-Axial) ERS?

Bonus: Is a Selecon Pacific an axial or radial?

Standard QotD rules apply on all including bonus questions.


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## derekleffew (Oct 11, 2010)

Double bonus: How about the Kliegl Bros. 1357 series?


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## gafftapegreenia (Oct 11, 2010)

To add to that, what is a Profile Spot, such as a Strand Patt. 23?


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## MNicolai (Oct 11, 2010)

QotD rules apply?


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## Grog12 (Oct 11, 2010)

MNicolai said:


> QotD rules apply?


Yeppers...


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## zmb (Oct 11, 2010)

An axial ERS has the lamp entering through the back of the reflector like a modern-day ERS while the a radial ERS has the lamp entering on the side of the reflector like many older instruments.

A Selecon Pacific is a axail ERS, the light leaves the parabolic reflector at a 90 degree angle to another reflector and then through the lenes.


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## Les (Oct 11, 2010)

Why the names 'axial' and 'radial'? Axial in relation to what, and radial in relation to what?

So, now we have a multi-part question.

What is the difference between an axial and radial ellipsoidal?
(not quite answered fully yet, IMO)

Is the Selecon Pacific Axial or Radial?

How about the Kliegl Bros 1357 series?

How is a profile spotlight different from an ellipsoidal spotlight?

Why the names 'axial' and 'radial'?


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## dcollins (Oct 12, 2010)

Les said:


> Why the names 'axial' and 'radial'? Axial in relation to what, and radial in relation to what?


Axial and radial in relation to the axis of the ellipsoid, which extends from the origin in the back to the opening in the front - the axis more accurately connects the two focal points, one of which is located at the lamp, the other is located near (I think just past?) the shutters/gobo slot. Axial ERSs have the body of the lamp in-line with the focal axis, while radial ERSs have the body of the lamp in a radial direction, like the spoke of a bicycle wheel.


Les said:


> Is the Selecon Pacific Axial or Radial?


Axial. The lamp is oriented in line with the focal axis - it's just that the focal axis then takes a 90 degree bend before it reaches the lenses. From the perspective of the lamp, it is still axial.

No idea about the Kliegl 1357 - it looks like a radial, but I can't find a good enough image or diagram, and I don't know about the specifics of a profile instrument vs. otherwise without looking it up. And I also have to go to class.


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## gafftapegreenia (Oct 12, 2010)

If I know my fixtures like I think I do, then I believe me and Derek are trying to get at a similar idea. Although, individually our questions are concerning different aspects of instrument design.


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## Grog12 (Oct 12, 2010)

zmb said:


> A Selecon Pacific is a axial ERS, the light leaves the parabolic reflector at a 90 degree angle to another reflector and then through the lenes.



There's something wrong in this sentence. What is it?


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## MPowers (Oct 13, 2010)

zmb said:


> An axial ERS has the lamp entering through the back of the reflector like a modern-day ERS while the a radial ERS has the lamp entering on the side of the reflector like many older instruments.
> 
> A Selecon Pacific is a axial ERS, the light leaves the parabolic reflector at a 90 degree angle to another reflector and then through the lenes.


 
Axial means a single ended lamp is placed in line with the beam axis of the instrument. I have never heard the term radial before. 

Until the invention of the ERS in the 1920's, claimed by several individuals and manufacturers, including messers Levy and Kook (LeKo) and the Kliegl Brothers (Klieg Light) lamps were designed as base down and the socket was placed below and in front of the reflector. This was true of Fresnels, PC's and Beam Projectors. The first ERS units used projector lamps which were designed to burn Base Up and to place the filament at the reflector focal point, entered the reflector at the top. On a left-right axis the lamp was centered, from front to back it was angled 45 degrees to the rear to allow for the "average" downward angle of the unit toward the stage and thus the lamp was positioned, "Base Up". The only lamps to ever enter the reflector from the side were the double ended lamps introduced in the 60's and 70's during the development of the quartz iodine lamps which became today's TH lamps.

The Selecon Pacific units 
Stage Lighting: Profile Luminaires
have an ellipsoidal reflector not a parabolic. The cold dichroic mirror is placed at a 45 degree angle to the beam axis, not 90 which would reflect the light back at the lamp. These units burn the lamp base down, thus rising heat moves away from the socket. The "cold" mirror reflects very little infra red and almost all the visible spectrum, thus the heat passes through the mirror and out the back of the unit via a heat sink, allowing a far cooler beam to pass through the lens.


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## Les (Oct 13, 2010)

Sometimes I think "radial ellipsoidal" was derived by us CB'ers, meaning that the lamp enters the reflector within the radius of the optics. Since this portion of the question has been all but answered by MPowers, I will throw my educated guess out there that the Selecon Pacific is, by definition, a radial ellipsoidal since the entrance to the lamp is not on axis with the optics; hence it is "non-axial". 

I have always thought that axial vs non was referring to the lamp's relation to the optical system, as opposed to the lamp's relation to the reflector. 

I have also heard 'radials' being referred to as 'top-loaders' because you load the lamp from the top, unless you hung it wrong.

To me, the Selecon Pacific isn't necessarily a new idea as far as technology is concerned. We've been using a bulkier version of it for decades, called the overhead projector. OHP's probably don't use a "cold mirror", but they do in fact remove a lot of heat from that 360 watt lamp. Another differentiating quality of OHP's is the fact that they use the micro fresnel lens as part of the optical system -- something not found in a Selecon Pacific to my knowledge.


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## MPowers (Oct 14, 2010)

> I will throw my educated guess out there that the Selecon Pacific is, by definition, a radial ellipsoidal since the entrance to the lamp is not on axis with the optics; hence it is "non-axial".
> 
> I have always thought that axial vs non was referring to the lamp's relation to the optical system, as opposed to the lamp's relation to the reflector.



Les, 

I would respectfully disagree with you here. IMHO, the Selecon Pacific is an axial system. The optical system, the optics, begins with the lamp and the primary reflector. When the optical path of the light is formed, it is formed exactly as it is in all axial systems, i.e. the lamp, is inserted in line with the axis of an ellipsoidal reflector, placing the primary portion of the filament at the nearest focal point of the ellipsoid. The light field formed is about an axis progressing in a straight line toward the secondary focal point the the ellipsoidal reflector. Due to a secondary reflector, the optical system takes a 90 degree turn for the light to reach the second focal point and the lens train, but everything is still in a straight line from the lamp filament to the last lens in the system. 

The optical system of many projectors use this same principal. Kodak Carousel projectors have used this 90 degree reflector system since the 1980's and all of the ultra high intensity adaptations and aftermarket lamp assemblies for that projector take advantage of the increased optical path and the cold mirror technology to reduce heat at the slide aperture (in theatre terms, shutter position and Gobo slot). It just took a while for theatre instrument engineers to say, "hey, that's a cool (pun intended) idea! and figure a way to make it work for stage lighting units. Of course video projection and LED video walls have all but spelled the doom of carousel projectors and the various computer control programs and dissolve unit systems like Dove and Genesis et.al. 

IMHO the Selecon Pacific is an axial unit as the lamp is in axial alignment with the path of the light from the filament to the light beam exit from the lens train at the other end of the unit.


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## gafftapegreenia (Oct 14, 2010)

I know that CB did not invent the term Axial as at least one manufacturer off the top of my head uses the word in its data sheets L&E
http://le-us.com/sitebuildercontent/sitebuilderfiles/ellips6.pdf


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## Sony (Oct 14, 2010)

To add to gafftapegreenia, I have heard MANY lighting designers refer to the older "top-loading" fixtures as Radials, people who have been in the business for years and have never even heard of Control Booth. It may be a regional thing, but I know in New England the term radial is used quite a bit.


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## MNicolai (Oct 14, 2010)

I've always understood radial to be a valid term since long before I joined CB, albeit a dying one since most manufacturers have adopted an axial design for their fixtures as fewer and fewer fixtures use radial designs.


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## venuetech (Oct 14, 2010)

> How about the Kliegl Bros 1357 series?


 
Interested?
look at what style lamp base the unit uses.


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## derekleffew (Oct 14, 2010)

MPowers said:


> ...I have never heard the term radial before. ...


 

Les said:


> Sometimes I think "radial ellipsoidal" was derived by us CB'ers, ...



From the Discussion section to the term radial in our wiki:

derekleffew said:


> ...Also, one member has pointed out that this is a slang term for what he and everyone else in NYC referred to as Incandescent ERS, as they fell out of favor once the T/H lamp came in.
> 
> STEVETERRY said:
> 
> ...



"Radial" isn't entirely accurate, as an ellipse has no radius (nor does it have focal points--it has two foci; lenses have focal points, reflectors have focuses); then again, neither is "incandescent".

See also the collaborative article Ellipsoidal Reflector Spotlight-Ancient History - ControlBooth .


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## mstaylor (Oct 14, 2010)

I learned it as radial but I can't remember how far back. It was in the area of 1984 but it could have been either side of it. Of course, I'm east coast so it may have just traveled south.


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## MPowers (Oct 14, 2010)

derekleffew said:


> "Radial" isn't entirely accurate, as an ellipse has no radius (nor does it have focal points--it has two foci; lenses have focal points, reflectors have focuses); then again, neither is "incandescent".




From the Random House dictionary:

fo·ci
   /ˈfoʊsaɪ, -kaɪ/ Show Spelled[foh-sahy, -kahy] Show IPA
–noun
a pl. of focus.
======================

fo·cus
   /ˈfoʊkəs/ Show Spelled [foh-kuhs] Show IPA noun, plural -cus·es, -ci  /-saɪ, -kaɪ/ Show Spelled[-sahy, -kahy] Show IPA, verb, -cused, -cus·ing or ( especially British ) -cussed, -cus·sing.
–noun
1.
a central point, as of attraction, attention, or activity: The need to prevent a nuclear war became the focus of all diplomatic efforts.
2.
Physics . a point at which rays of light, heat, or other radiation, meet after being refracted or reflected. 

===========================

focal point
 
–noun
1.
Also called principal focus. Optics . either of two points on the axis of a mirror, lens, or other optical system, one point being such that rays diverging from it are deviated parallel to the axis upon refraction or reflection by the system and the other point being such that rays parallel to the axis of the system converge to the point upon refraction or reflection by the system.
2.
the point at which all elements or aspects converge; center of activity or attention: The focal point of our discussion was the need for action.
3.
the central or principal point of focus.

As Foci is simply plural for focus and definitions 2 for focus and 1 for focal point would seem to be directly applicable to an ellipsoid, I would respectfully argue that an ellipse and thus ellipsoidal reflectors, do indeed have focal points.


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## Grog12 (Oct 14, 2010)

I heard the term "radial" long before CB even existed. 

We've got votes in both directions for the Selecon..what about the Kliegl Bros. 1357 series?


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## derekleffew (Oct 14, 2010)

Note the the Kliegl 1357:


most often uses the 1000W DWT lamp:


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## Les (Oct 14, 2010)

derekleffew said:


> Note the the Kliegl 1357:View attachment 3807
> 
> most often uses the 1000W DWT lamp:View attachment 3806


 
Erm... Bi-radial!


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## derekleffew (Oct 14, 2010)

Les said:


> ... Bi-radial...


Nope, that means something totally different, at least to noise-boyz:

Horn loudspeaker - Wikipedia, the free encyclopedia
I always liked the term "baby-butt horn."


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## justind (Oct 14, 2010)

i'm going to go with 'neither axial nor radial' for the kliegl.

selecon pacific model no. is not specified so i'll go with: "a selecon pacific is a company"

axial and radial refer to the point at which the lamp penetrates the reflector, respectively either inline with the foci or off to the side (i'm don't think there is a specific angle that is used as a standard). The pros/cons are differences in the evenness of the field of light/efficiency of heat sinks and vents.


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## Grog12 (Oct 14, 2010)

justind said:


> i'm going to go with 'neither axial nor radial' for the kliegl.
> 
> selecon pacific model no. is not specified so i'll go with: "a selecon pacific is a company"
> 
> axial and radial refer to the point at which the lamp penetrates the reflector, respectively either inline with the foci or off to the side (i'm don't think there is a specific angle that is used as a standard). The pros/cons are differences in the evenness of the field of light/efficiency of heat sinks and vents.



You're not getting away on the Pacific that easy...by your own definition you should have a better answer.


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## derekleffew (Oct 14, 2010)

Grog12 said:


> You're not getting away on the Pacific that easy...by your own definition you should have a better answer.


I don't see how it matters whether the Selecon Pacific is a 5.5°-13°, 12°-28°, 14°-35°, 23°-50° and 45°-75° Zoomspot, or 5°HE, 20°, 30°, 40°, 50° and 90° Fixed Beam, OR uses a light source of Tungsten Halogen Mains Voltage, Low Voltage 80V, 575W MSR Discharge Arc, or 70W/150W CDM.


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## justind (Oct 15, 2010)

geez just trying to bust your chops. selecon pacific makes products that don't even have reflectors in them!

but for the list of models you mentioned i'd have to go with axial.


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## Grog12 (Oct 15, 2010)

justind said:


> geez just trying to bust your chops. selecon pacific makes products that don't even have reflectors in them!
> 
> but for the list of models you mentioned i'd have to go with axial.



Let me bust yours back. Selecon makes products that don't have reflectors in them...Selecon Pacific is a very specific line of lights. Kind of like the difference between ETC's Source 4 ERS units and ETC's Selador series.


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