60's era Klieglight (ERS) Step Lenses

[church]

A fresnel lens and the colouvred lens are not actually the same thing. A colouvred lens actually behaves the same as solid concave lens and are capable of producing a hard focus - the advantage of this lens is it is lighter than a standard lens and cheaper to manufacture in the 40s through the sixties the disadvantage is that it is not as efficient. However it is essential that the opaque paint is in place otherwise the light spread and focus is lost brcause you have additional edges for refraction of the light.

The fresnel lens is efficient but is not able to produce the sharp focussed image of concave lens.

As someone has already mentioned Strand offered a number of profile spots with a fresnel lens option, namely: Patt 23 and patt 263. Some of the earliest Patt 23s came with a colouvred lens although I have only seen this on three fixtures in Canada out of the 100s of patt 23s that I have touched on both sides of the Atlantic I have also seen colouvred lenses on Strand Century radial lekos, electro controls radial lekos and Klieg lekos plus another Canadian manufacturer. If you know the focal length of the colouvred lens you can usually just replace it with a concave lens of the same focal length. I assume most people know how to check this but for those who don't a quick method is hold the lens horizontally above a piece of printed paper and measure the height from the paper to the lens for the writing to be in focus. The height is the focal length.

I just threw out six 6*6.5 and three 8*12 colouvred lenses.

 

[gordonmcleod]

Often the stepped lens was used to reduce the overall thickness of a lens to reduce the risk of heat breakage
A single 6x6 stepped lens ellipsoidal is the same as a two PC lensed 6x12 ellipsoidal but a lot lighter
The Strand Patt 263/264 was available with a stepped lens that was stepped on the front like a fresnel lens (listed as a colouvered fresnel lens
The pat 23 had the steps on the back side

 

[pianoman]

I'm resurrecting my own old thread because I noticed some new things when I pulled out the old Kliegs this week. I noted before that the wide angle fixtures I have produce these weird outer "phantom" rings of light, at about half the brightness of the inner ring, which are not affected by the shutters. Looking at the instrument last night, I noticed that if you look at the lens while the light is on (not directly in the light, but off to the side), the outermost "step" in the step lens is lit about half as brightly as the other inner rings. I tried repositioning the focus tube and even moving the lens to the other lens position for the narrow angle lenses, but neither made a real difference, other than making the light unfocusable. Part of my problems is likely related to the lack of paint on the perpendicular edges of the rings on the lenses, but I think there's a bigger issue here. It's quite possible that while reworking these instruments before I took them I rearranged parts into the wrong instruments. Kliegl did not differentiate the labels on the instruments to note whether they were wide angle or narrow angle, but I'm wondering if perhaps the two types used different reflectors or something like that. It's the only explanation I can come up with, as I looked at the lamp sockets and they all seem to be adjusted fairly randomly, and swapping them out between fixtures made no significant differences that I could see.

Does anyone have more technical experience with these fixtures that could help me "shed some light" on this situation? (har, har har...)

Thanks,
Dan

 

[ship]

As with the above, one first assumes the proper lens train on a fixture and bench focuses it With some work if such a bench focus cannot be achieved one might move onto the next fixture in do the simple first.

Get rid of those fixtures that can get the hard edge first in doing the easy first.

After that, should only be a few few fixtures that cannot be bench focsed. Next in doing the easy, obviously swap lens trains between fixtures in seeing if perhaps easy is possible in past mistake.

If not there, extract the lenses from a known to be good similar size lens train fixture and compare lenses if standing up on the round with each other. Shorter and they are probably more narrow in focus.


After that if similar in lens train and barrel to the fixture, if lenses are the same you have a serious problem, perhaps the wrong lamp or not enough time during bench focus?


Overall concepts.