Vintage Lighting Leko w/ a Fresnel Lens

derekleffew

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Say it ain't so!

I was perusing a newly-discovered online 1960 Century Lighting catalog which contains this page:
CENTURY CAT 1960  033.jpg



I'm not sure even @JonCarter or @STEVETERRY are old enough to know of these.

But a long-time mystery of mine has finally been solved, "Why was the most common Kliegl Bros. ERS the 1355 equivalent to a 6x8 (single lens), when everyone else was 6x9 (double lens)? Kliegl was copying a nearly ten year-old Century practice.
 
strand made a Patt 263 which had a fresnel lens and worked quite well the 264 was identical but had a p.c. lens, the 263 was easier to blend.
 
Interesting that in the literature Century never says Fresnel, but that's clearly what it is.

Just to clarify (how I learned it):
Refraction: In a lens, it's the surfaces that matter. Theoretically, glass can be removed from in between with no ill effects. This means lenses can be stamped rather than ground, leading to lighter and thinner lenses, with less light lost due to transmission.

A plano-convex (PC) lens has one flat side and one curved side. ^1
A step (stepped) lens has a curved side and series of flat segments. ^2
A Fresnel lens has a flat side and series of curved segments. ^3

^1. The greater the curve, the shorter the focal length.
^2. When used in an ERS, the risers (vertical portions) are often coated black in order to lessen halation, but can lead to "bullseye target" artifacts in the beam.
^3. When used in Fresnel fixtures, the flat side has some pattern of stippling to soften, diffuse, and further homogenize the beam.
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I've used (what I now think must have been) 4 1/2 x 3 1/2, but at the time we called them 4 1/2 x 6 1/2 step lens, Lekos. Never seen the 6x8 or 6x11 step from Century.

Harkening back to this thread on Altman radials, note the wider Lekolights are not recommended with 750 watt lamps.
 
8 x 9's and 8 x 11's supplied as part of original house stock upon opening Hamilton, Ontario, Canada's "Hamilton Place 'Great Hall' in September of 1973.
We had 8 x 9's and 8 x 11's with both lens types and you're correct; the Fresnel lensed models could / would NOT focus as sharp as the PC's.
We also had half a dozen 8 x 16's but all of the 8 x 16's were supplied with PC lenses for use as FOH specials,
Toodleoo!
Ron Hebbard
 
I used those century fixtures in High School. Man those mothers were heavy. Oh and yeah "sharp focus" was not really achievable.
 
Just to clarify (how I learned it):
Refraction: In a lens, it's the surfaces that matter. Theoretically, glass can be removed from in between with no ill effects. This means lenses can be stamped rather than ground, leading to lighter and thinner lenses, with less light lost due to transmission.

Derek
My understanding is slightly different. We use step / fresnel lenses because thay are thinner. This leads to less heat build up in the glass, and reduced chance of breakage due to heat. This is why ( IMHO) a fresnel lens in an old style fresnel fixture does not crack as often as a 6x9 in an old altman or century fixture.

Who has used an ERS with a fresnel lens? Guessing even less sharp than a stepped lens.

Anyone who has used a 5 degree Source 4?

Remember we think of fresnel lenses as soft because for the fresnel fixture, they purposely make it crappy by putting a stippled back on it so you would get an even soft field.
 
We use step / fresnel lenses because thay are thinner. This leads to less heat build up in the glass, and reduced chance of breakage due to heat.
Yeh, I meant to add that. But I think it's a by-product and not the primary reason. First reason is the cost to grind a PC lens vs. stamping/casting a step/fresnel lens.

Anyone who has used a 5 degree Source 4?
Ding ding ding! 🛎 S4-10° also.
 
well thanks, I have never seen a step lens.
 
Well, never too old to learn. I maybe realized it but didn't know that Fresnel lenses vary a lot. Some are concentric rings of prisims - all surfaces planar - and some are closer approximations of a pc lens with radiused tings. And the consistency of that curved front surface varies - some concentric and some to a common focal point.

But I don't think fresnel includes stepped lenses.

And I'd love to learn the geometry if the S4 5 degree.
 

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