Axial and Radial l ERS
- Thread starterGrog12
- Start date
Double bonus: How about the Kliegl Bros. 1357 series?
To add to that, what is a Profile Spot, such as a Strand Patt. 23?
Yeppers...
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.
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.
Les
Well-Known Member
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'?
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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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.
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.
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.
MPowers
Well-Known Member
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
Well-Known Member
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.
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
Well-Known Member
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.
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
http://le-us.com/sitebuildercontent/sitebuilderfiles/ellips6.pdf
Sony
Active Member
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.
From the Discussion section to the term radial in our wiki:
"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 .
MPowers
Well-Known Member
"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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