With the thought of both concentrating the original beam of the SunDrop hosting the Nichia 083 as well as allowing the head to be host of light engines based on other LEDs with greater height, the SunDrop XR-U head was designed. The XR designates extended range, extended reach as well as compatibility with the Cree XR LED. I decided to throw in the U to designate universal although it may be broader in scope than reality would permit. Certainly there are a number of different LED's that could work below the sapphire lens in the XR-U head.
The lens in the XR-U is approximately .125" further above the LED compaired to the original SunDrop and the head shows this in the extra length. From the front end, the LED is magnified further in the XR-U (left):
I did some testing and evaluation of this head with a number of light engines:
The Nichia 083 and Cree XR-E light engines have been used in the original SunDrop and the Haiku, respectively. The Seoul P4 High CRI proto and Cree MC-E proto were built just for test and evaluation purposes.
The following beam shots were all taken from the same position with a Nikon D300 using a 20mm lens and exposure was the same manual setting for all. I consider the exposure and intensity of light seen in the images as reasonable based on a vision that has adapted to the dark in which the lights were photographed.
I also put the XR-E light engine in a Haiku and the Seoul P4 High CRI light engine in a prototype Aleph head hosting a McR-27S reflector to get some sample collimated type beam shots for comparison to these flood beams.
The 3S drivers in the XR-E and Seoul P4 LE's are both set at ~ 600 mA on high level. The MC-E light engine is closer to 700 mA driving the 4 dice in parallel. The Nichia 083 LE is at ~ 330 mA.
There is measurable light loss with the XR-U head compared to the original SunDrop head because the lens is further from the LED. In the cases of the other LED's, their die are closer to the lens and the domes over the die wouldn't allow them to be situated much closer than they are.
In some comparisons made with the integrating sphere, it was interesting to see not only a drop in flux on the SunDrop VS SunDrop XR-U but a change in the measured CCT as well. Although the flux dropped, the CCT increased from 5600k to 5800k with the same Nichia 083B LE.
Spectrum and color info on the sample 083 based XR-U head:
Since I was evaluating the Seoul P4 High CRI LED, I also tested it in the integrating sphere while mounted in a XR-U head:
The outdoor beam shots don't show variations in tint or artifacts like a white wall would. In the case of the XR-U head, all of the light engines produced a relatively even and artifact free flood disk of light with noticible artifacts and tint variations limited to the perimeter of the disk. The Seoul P4 in the Aleph 27S proto (image below) has a noticible higher color temp in the spot portion of the beam compared to a warmer corona and spill, when viewed on a white wall.
The basic goal with the XR-U head is to provide a middle ground compromise between full flood (no secondary optics) beams and collimated beams which have high lux in their center and relatively low lux as you move from center out to the spill. The idea is to retain the even distribution of a flood but concentrated in a narrower viewing angle to allow you greater range. Using the Nichia 083 LED, I estimate the effective beam angle of the original SunDrop to be approximately 82 degrees and in the XR-U head, I estimate 53 degrees.
The effective beam angle I consider to be inside of any exterior rings or artifacts. The angle and extent of artifacts will vary among LED models used and be a function of the die size and its apparent distance behind the lens.
Unlike a typical TIR optic that consists both of a lens and a reflector redirecting that light that does not pass through the lens but instead hits the side of the TIR and bounces forward, there is inherent light loss with a lens only, floating above the light source. The closer the lens is to the source, the greater the angle of source light it will manage and redirect.
The XR-U head is clearly a compromise where you sacrifice some flux for an increase in lux.
In the case of the Nichia 083 and Seoul High CRI LED's, I believe the compromise is favorable if one seeks an even and clean field of illumination with greater reach than that available from say a mule configuration.
In the case of using a Cree XR-E LED, look at the beam shot of the Haiku VS the XR-E LED in the XR-U head. The same light engine is used and the overall beam angle coverage is very similar. In the case of the XR-U, the field of illumination is relatively even across the field whereas in the Haiku, the center is heavy in intensity with a drop in lux as you move off center.
I personally prefer an even field of view provided it is 1) bright enough and 2) covers the needed viewing angle. When either 1 or 2 can not be met, a tighter collimated beam or simply more flux need to be brought to bear or is it bare.
I have been turned off by many of the early lens based lights but I realize it is because the were designed to collimate tighter than I would like and as the projections were sharper in focus, the artifacts in the image were bothersome. The inherent tunnel vision in many of them made me think of them as a reflector beam but without the useful and sometimes necessary spill.
I have been real happy with the Haiku and its three levels and feel that is beam distribution works well both on the low and the high. However since most of my personal illumination needs are near to mid range, I figured a beam that had a similar angle of coverage but without the hot center could and would have some merit. In reality, that does seem to be the case.
The other thing I see favorable with the XR-U head is that it is friendly to multiple die LED's like the Nichia 083 and the Cree MC-E. Favorable at least in the core and interior of the beam. I grant that there are obvious artifacts at the perimeter but if the beam is adequate to more than cover the target of interest and provided it is on target, you aren't even looking at the outside edges.
For the sake of nomenclature and hopefully less confusion, I suppose SunDrop should be limited to the inclusion of the Nichia 083 and if this head is used with a LE hosting another LED, the designation of XR-U alone should be used?!? Regardless, it's confusing and I am easily confused.
One last observation I feel inclined to make is that there is something pure, simple and satisfying to me in considering the longevity and immunity of the sapphire lens to environmental degradation and threats that seems to be in sync with the titanium host itself.
And thus we now end yet another long winded introduction of yet another niche type light design.