Doug S
Flashlight Enthusiast
There may be some unrealistic expectation for the performance of the white high dome luxeons when used with the optics designed for the low dome devices. These collimators are a very clever design which utilize both refraction and total internal reflection [a.k.a., critical angle reflection] to collimate the beam. The problem with the high dome devices is that they emit a much higher percentage of their output far off-axis where the critical angle reflection will not occur and this light just passes out the sides of the collimator. It is illuminating to consult the DS23 datasheet for the "1W" devices and compare the high and low dome red devices with and without optics. The low dome device has a typical output of 25 lumens and the high dome device an output of 44 lumens, an increase of 76%. When fitted with optics, however, the low dome device has a typical peak intensity of 750 cd vs the 660 cd for the high dome device, despite the 76% higher luminous output of the later. The difference is largely due the the inability of the collimator to capture much of the output of the high dome devices. For those who wish to obtain a narrow beam using the high dome devices, a parabolic reflector such as one from a Minimag may produce better results. Ultimately, the side emitting devices, when available, will be the best bet for producing a tightly focused beam.
