How do you find the perfect filament/LED placement?

[smollerthings]

Hi y'all,

Is there a way to find the optimal filament placement when you don't have the original illuminator?

Thanks!

[dtsh]

I don't know about perfect, but I believe placement should be set depending on Koehler illumination. If you have full koehler, you would want to place it at the correct focal point which should be the same point at which the original lamp's filament would have been in it's focal plane (or here, fully unfocused). If you have modified koehler or the like where there's use of a frosted glass I think placing the light source so that the projected light most evenly covers the frosted glass surface would be preferred (seems more appropriate with the light cone from an LED). That seems to me to be the most logical, but that doesn't mean it's necessarily correct.

[BramHuntingNematodes]

Your illuminator should be able to cast a good image of the filament against a nearby wall

[smollerthings]

I don't think this is Kohler or modified Kohler. There are one lens immediately after the bulb, then a mirror, then another lens which is probably the collector lens?

[BramHuntingNematodes]

probably a ground glass element in there tell you what try aiming at a somewhat more distant wall and try get the dot about as small as you can should be a starting point

[smollerthings]

Just took it apart, no ground glass. See pics:



Per the video below at at 14:24, I should aim for projection of the filament at the condenser aperture (=iris?)

[BramHuntingNematodes]

oooh right depends on the type of condenser you have I got some that like collimated light rather than focused for using external illuminators

[Dubious]

Some of the led kits come with your choice of lens--i.e., spot, medium, wide. I assume you would not want to use that lens but would instead rely entirely on the existing halogen optics? On the other hand, halogen illuminators often have a reflector behind the lamp which, given the geometry of the led, generally cannot be used with the led.

[smollerthings]

Some of the led kits come with your choice of lens--i.e., spot, medium, wide. I assume you would not want to use that lens but would instead rely entirely on the existing halogen optics? On the other hand, halogen illuminators often have a reflector behind the lamp which, given the geometry of the led, generally cannot be used with the led.

I actually realized I miss half the original optics because I only have this (below) without the original lamp that goes inside the illuminator. So I may just see what it looks like with the spot optics and wing it. I tried just putting a halogen bulb inside of it and it was a disaster. One sees the filament more clearly than the slide

[Dubious]

Seems reasonable. I migbt order the medium lens as well, to see which worked best.