On 16/03/17 22:36, Jeff Liebermann wrote:
On Wed, 15 Mar 2017 10:40:29 +0100, Sepp Ruf
wrote:

Jeff Liebermann wrote:
On Tue, 14 Mar 2017 20:27:09 -0500, AMuzi wrote:

Claims 'projector' lensing as opposed to 'reflector' lensing.
I don't know
http://www.herrmans.eu/start-english...?familyId=2209

More like a lens versus a reflector. There are benefits to both. I'll
skip the basics

You shouldn't.
https://www.youtube.com/results?sear...ry=h-black+pro

Mid-field looks too bright and transitions don't look smooth. Not going to
buy one.

http://www.herrmans.eu/start-english/products?familyId=2209

There are several videos on this light under H-Black Pro. Two of them
looked ad agency creations showing mostly how happy the rider looks on
his bicycle with its new headlight. If there was a chance to see the
beam pattern, it was conveniently obscured by the ad agency by
covering it with moving white spaghetti. However, this video looks
like a genuine review:
"Herrmans H Black Pro - First look"
https://www.youtube.com/watch?v=RLaI1Y54gHo
The interesting part is that not only does he show the beam pattern on
the ground, but at the very end, he estimates that the light produces
230 lumens and 90 lux. If the beam was truly uniform on the ground,
then the size of the beam pattern would be:
1 lux = 1 lumen/square-meter
230 lumens / 90 lumens/sq-m = 2.56 square-meters
which does seem to match the beam pattern area in the video.

However, there's a problem. If you look at the 0:19 on the video, you
can guess the range of the light. Based on the distance between the
headlight and tail light, I would guess(tm) that the far end of the
beam is no further away than twice that distance, or 1.3 meters, which
is far to close for a headlight pattern, unless I were dodging
potholes in the road. If the beam were elevated properly, so that I
could see perhaps 5 meters ahead, the 2.6m^2 pattern area becomes
about 16 times larger, or 41.6m^2, and the 90 lux brightness drops to
5.6 lux. This not particularly bad and is my guess(tm) similar to
what a commodity 2 watt LED headlight will produce.

The beam pattern in the video looks like 3 overlapping circular
"spots" of equal diameter. I suspect what the designer was trying to
accomplish is provide equal brightness (lux) on the ground. The
nearest spot beam gets some amount of light from the lens with a
fairly wide beam width. The middle spot gets the same amount of
light, but is more tightly focused (narrower beamwidth) and therefore
produces the same brightness (lux) on the ground. The most distant
far spot gets the same amount of light, but with an even narrower
beam, also producing the same brightness. At least that's my
guess(tm) as to what was suppose to happen.

However, it didn't work, and as you note, the transition areas where
the spots overlap are not even brightness with multiple hot spots. It
rather reminds me of my experiments with multiple independent LED
headlights. The idea was to shape the beam pattern by individually
adjusting the position of each LED light. (I didn't go so far as to
adjust the intensity of each). With 5 LEDs, I ended up with 5 hot
spots. Oops. I still think there's promise to the approach, but it
would take considerable cut-n-try tweaking, as Barry Beams has done
with his headlight.

The advertising for the light claims:
"The light pattern is optimized for the rider - super wide, long
and homogeneous light distribution (widest on the market)."
Well, it's not very wide, judging from the video and from the pattern
on the data sheet.
http://www.herrmans.eu/start-english/products?familyId=2209
It's also not very homogenous, which I presume means evenly
distributed light. That's what I would expect from a film or slide
projector, where any brightness irregularities across the projected
image would be highly unacceptable.

Take a look at 12s in. Here the light is set up as my IQ-X is, with the
top of the beam angle down a few degrees (SvTO cutoffs really help this)
and it seems the near field is indeed to close. I should try and film
my IQ-X in action, it has a very similar beam pattern, but less
delineated. Mind you, twice the price.