Finally got the chance to power up my first two fixtures of these type. I was using an Ushio lensed BAB lamps which are only 36 degree but all I had in stock at work.
In answer to will it work, yep, it works in a similar way to the old lamps work by way of a sort of harsh light effect but one that's period as it were in doing so. Very similar in fact except that the color temperature is much higher and the fixture efficiency was boosted.
So first I tried the PC lensed fixture. On paper photometrically, given the approximate center point of the filament on a 400G/FL lamp designed for the fixture, it's a 45 degee angle if the filament of the MR-16 is placed in the same position in a reletive sense. In other words, one wants a 45 degree beam spread by the math and I did do the math and even lay it out in drafting it up.
The 20w BAB lamp is a bit under powered in comparison with what I remember of a 400w lamp but that's the design intent to be not as bright.
More important beyond intensity is what each of the two
Fresnel and PC lenses did when a MR-16 lamp was powering them up.
The PC
lens was tried first. In spot position, stridations from the
reflector upon the beam image were miserable and clearly showing. This would be a really bad choice for a lamp/lens. IN flood position, it wasn't that bad all together. Towards the edges of the beam there was still stridations from the reflector but it was a fairly even beam other than this and a frosted
gel would cover for this. I also could not get the beam to bench focus with a hard edge I should be able to. This was possibly due to the beam angle of the lamp used, or perhaps being not so centered. This lamp, lens and position however was the closest to doing an honest hard edge and flat field focus however. Just about there in being as one would expect with a PC lens fixture. That is an MR-16 lamp powering up a antique PC fixture.
The Fresnel lens was miserable in all ways. Spot position was less bad than flood position but overall, you could while not seeing clear stridations, there was absences or shadows in the beam that got worse the more you sent the lamp towards flood position. It will be a tremendous savings of money to me in not having to replace all lenses with a Fresnel, but who knows once I do the 40 degree, much less 60 degree lamps what will work best. This by way of soft image verses hard PC image.
The grainy image of a Box spot I remember was definately gone in both cases due to the change of lamp. Much more like a modern stage light instead of antique effect.
What's learned... First if it's a 45 degree fixture, the 36 degree reflector lamp seemingly is not optimal for use in it. I have some GE brand 40 degree lamps on order and will try them. As a theory I might in flood position for the PC lens be able to get really close in flood position to a good tight bench focus beam with a hard edge. This in between spot and flood should also work theoretically very well.
Otherwise in this experiment, there is BAB/60 lamps available with a 60 degree beam spread. If I cannot get a bench focus off the 40 degree GE lamps, the next choice is something from Ushio, Osram, or Dura Lamp that is available in 60 degree. Also, given the fixture is enclosed and lensed, a lensed version of this lamp is optional in a won't hurt but won't be needed type of way.
That's part two of this experiment. What will the closer to the beam angle of the fixture 45 degree, by way of MR-16 lamp, 40 degree or 60 degree lamps do in the fixture?
Overall, if you have to, and in doing so, the PC lens with so far the MR-16 lensed BAB lamp with 36 degree beam angle is not that bad in a classic 1920's box spot with PC lens in flood position.
There is our answer, it's a promissing concept this more efficient lamp within a antique fixture.