Thanks. So, when zooms in where should the lights go? Originally, I though the amount of the lights emitted should be the same. They just concentrated in a smaller area. Not true? In the case of using a good IS, should the reading the same, or at least similar?
Zoomed in should be around 40-60% of the lumens of flood. The exact amount mostly depends on the focal length of the lens. The loss is due to light that hits the side of the head instead of hitting the lens.
Thanks for sharing your experience. What you said make sense. 40 to 60 percent is also a good rule to follow. I tried a few of zoomies and they all in this range.
@twinclouds: in my sig-line is a link to a test of the light loss in a zoomie
I checked out your link. It is really very comprehensive and helpful. Good post! Thanks.
Do you have any result on the loss in a thrower?
With my current setup, given the lens rests on top of the pipe, it's currently favoring throwers given the flood is being cut-off by the slight step-down at the edge. I'd like to take a quick poll to see how many would be interested in a custom cut UCL lens? It'll be 114mm (just shy of 4.49") in diameter. Of course cost is a factor but if we can drum up enough interest, we might have group buy on our side.
I'm currently limiting it to US folks given the shipping logistics but of course it'll all depend on the interest.
Show of hands folks?
I just tried out my PVC Light tube (built with 3" pipe, painted matte white inside, glass shelf, etc. . .) for the first time yesterday and I noticed that if I move my light around (i.e. to the inside of the 90 degree elbow from center of the glass) my lux #'s jump up pretty significant (I'd see numbers from about 880 to 1030 - lux #'s, not lumens). I don't trust my lux meter as it was giving me ridiculously low lux readings on my Courui so I am waiting to buy a better one. In the meantime I thought I could use this cheap lux meter to at least compare relative #'s. The jump in lux reading has nothing to do with outside extraneous light by the way. So is this normal? Just go with the lux reading with the light centered? (This is a 2x XM-L2 bike light in the neighborhood of 1,400 lumens by the way.) Or is my issue that I'm only using 3" PVC? Here's a pic (red rag just happened to be handy, I have foam to use and I was measuring with room lights off):
-Garry
Consistent positioning is extremely critical with these. We use dark foam cutouts to seal around the flashlight head, but also to keep the light pretty well centered on the glass. I'd only use 4" pipes - dunno about characteristics with 3" pipes. TurboBB knows more bout these, so can maybe help.
Sorry TurboBB - I'm looking to migrate off my pipe lightbox and build up 1 or 2 sphere based ones, so not looking to improve on my PVC lightbox. I think I'll get more consistency out of it for flooders, throwers, etc., lights that vary tremendously in lens size, optics, LED counts, etc.
Thanks Tom. I'll have to see how things go once I get around to getting a better light meter.
-Garry
No need to be sorry at all, this was just some idea I threw out years ago as I thought it worked pretty well. However, the more lights I've run through it, I realize there are definitely limitations. Chief amongst this is the positioning and calibration which I do ahead of each runtime or measurements that I plan on posting. The positioning is important thus I use the paper templates but I also notice that the range used on my HD450 meter can be percentage points off between say the 400 vs. 4K range. Then of course comes the difference between flooders/throwers but of greater impact is the size of the bezel and number of emitters.
Ultimately it was a great experience to learn from and while I can't say that I've completely abandoned any further improvements/developments just yet I do plan on building a DIY IS sometime in the future.
@Garry - Re: 3" pipes, while I've never tested it myself but I'd speculate that given the overall smaller dimensions, it would negatively impact the "accuracy" as there is a smaller margin for error so positioning will be critical. Try using paper/cardboard templates cut to center the light perfectly within the intake hole.
Thanks for the feedback TurboBB.
-Garry
Did you guys bother filling the joints on the inside of the tube formed with 90’s?
Also, would plexiglass be okay for the platform or are we dealing with too much heat?
I actually glued the pipes together (unless you meant the interior in which case I didn’t bother sanding it down as I always calibrate ahead of each run now). As for plexiglass, I’d strongly recommend against it especially if you plan on testing larger hotter running lights (e.g. TN36 UT got up to 160F during my runtime testing). Better to find a thin piece of glass (any will do since each light will face same penalty shining through it).
Can anyone tell me where the first appearance of this pipe device was?
Can’t find the post now but I read it on CPF and it was just a conception, no actual device made (as far as I know)
EDIT: Found it! http://www.candlepowerforums.com/vb/showthread.php?326078-Estimate-Lux-amp-Lumens-with-Light-Meter-LumenToob
I meant the gap/joint between the 90’s in the interior of the tube. I squeeze them together as tight as I can, but there’s still a fairly sizeable gap that interrupts the otherwise smooth tube.
I was thinking about filling the gaps with caulk or something, but I have no idea if that will help/hurt or just be a waste of time.
Awesome. Thanks
When you guys use your light pipes and spheres, do you prefer the foot candle setting or the lux setting on your meter and why?
I always use lux because the ANSI standard is in lux, so it makes the numbers more easily compared to other lights. Plus its easier to calculate the throw from lux, again probably because that’s how the ANSI standard is set up.
since Im only testing AAA lights, this works for me
the vitamin jar cap has a couple of pieces of paper to “calibrate” it so I can read lumens without a calculation.
“calibration” is based on a ReyLight CuTool that has a claimed 1 lumen low.
here you can see the calibration is reasonably accurate, the pictured Worm has an 80 lumen spec on high:
I have found the light meter is very helpful to determine relative brightness between my lights. I also use it to plot runtime curves, so I can tell if a light is regulated or unregulated… (I have 2 ReyLighs, one is regulated, one is not)
