The Nightsword project

[get-lit]

Ah ok Onestep now I see the light :grin2:


Sven, I just remembered using the experiment I did with taping off sections of the reflector with electrical tape, no camera needed...

First tape off the reflector leaving just the inner ring. Then take a Lux reading right at the aperture parallel with the concentric center of the ring. Then take a Lux reading right within the beam center from very far away.

Next tape off the reflector leaving just the outer ring of the same "apparent" forward-facing thickness as the inner ring. Then take a Lux reading right at the aperture parallel with the concentric center of the ring. Then take a Lux reading right within the beam center from very far away.

Compare the results. The Lux reading of the inner ring will be brighter at the aperture due to greater light gather, and the Lux reading of the outer ring will be brighter far away due to greater collimation. The greater the distance measured, the greater the difference.



EDIT - Here's with some example renders of the dynamic using a short FL reflector and uniform source:

With the whole reflector...

Just the outer half exposed...

Just the inner half exposed...

These are brightness-balanced to the peak illuminance of the whole reflector. Notice the differences in illuminance, beam size, and light gather. These variations would be greater when using rings thinner than half the reflector.

 

[sven_m]

First tape off the reflector leaving just the inner ring. Then take a Lux reading right at the aperture parallel with the concentric center of the ring. Then take a Lux reading right within the beam center from very far away.

Next tape off the reflector leaving just the outer ring of the same "apparent" forward-facing thickness as the inner ring. Then take a Lux reading right at the aperture parallel with the concentric center of the ring. Then take a Lux reading right within the beam center from very far away.

Compare the results. The Lux reading of the inner ring will be brighter at the aperture due to greater light gather, and the Lux reading of the outer ring will be brighter far away due to greater collimation. The greater the distance measured, the greater the difference.

In great distance the Lux reading for the outer ring (for same ring thickness) has to be much higher, just because the apparent area alone is much bigger. I see no way to distinguish a possible focal distance effect from this. You could try to make equal areas, but--what a hassle...

The apparent luminance is a much easier way: the human eye measures light per area automatically :-)

 

[get-lit]

Making equal apparent areas is easy, first determine the apparent area of the outer ring:

A = ((OD/2)^2 x 3.14) - ((ID/2)^2 x 3.14)

Then determine the inner ring OD of equivalent apparent area:

OD = ((A + ((ID/2)^2 x 3.14)) /3.14)^1/2 x 2

All together:

InnerOD = (((((OuterOD/2)^2 x 3.14) - ((OuterID/2)^2 x 3.14)) + ((InnerID/2)^2 x 3.14)) /3.14)^1/2 x 2

This is a slightly different comparison than comparing apparent brightness with the eye or with a camera, in which case you'd be looking at equivalent apparent thickness. When sectioning the reflector into halves using equivalent apparent area instead of equivalent apparent thickness, the inner ring extends into the outer region of the reflector so it's not the ideal comparison to illustrate the dynamic, but it still works...

Just the outer ring exposed (12"OD, 9"ID, 49.47""A)

Inner region plus some outer region for equivalent apparent area (8"OD, 1"ID, 49.47""A)

Even with the inner ring extending into the outer region, the outer ring still has double the illuminance at distance due to greater collimation, even with just 1/14th of the light gather.

The reason I like Lux tests over telephoto camera is that the camera won't give much in the way of calculable figures, but it would be a good way to visualize the dynamic.

 

[get-lit]

Touch panel samples arrived...

On the left are working sample panels blacked out so they can't be used.

On the right are the samples of the thicker and hardened glass I plan to order, again unusable other than for endurance testing.

Cable required to make the connection to the controller board. 2,000 panels and 2,000 cables adds up.

First impression is the size is perfect. Time to beat on some glass.

 

[get-lit]

I've shored up the hardened glass along the edges and they don't break when pressing so hard it hurts both my thumbs at once. These will do. Next is testing with the controller board for resolution and accuracy.

 

[BVH]

Not sure I understand "blacked out so they can't be used" and then in the next post - "next is testing the controller board for resolution and accuracy". Do you not use a panel for checking board accuracy and reso? Why do the sample panels not work?

 

[get-lit]

The clear ones don't have the touch sensor components included, it's for testing durability only. The black ones work for testing the electronic touch capability, but are painted so that you can't see through them so they can't be used in an end product. This is done so that someone doesn't order samples just to use them without intending to place an actual order.

 

[BVH]

If you can't see thru them then how are you testing for reso and accuracy?

 

[get-lit]

There are tiny white dots on the black paint. When I touch a dot, it should change the electrical resistance of parallel pairs of horizontal and vertical leads connected to the controller board that translates those resistances to X and Y coordinates. The resolution depends on the degree of resistance variation per change in touch position. I'm sure it will be fine but have to confirm before placing the order.

The protected aluminum coated retro-reflector also just arrived, so I can test to see if that coating can withstand the temp or if I have to go bigger to keep the surface further from the lamp envelope. Lots to get done and also have to get caught up with work that pays the bills.

 

[BVH]

OK, got it now. Of course do the work that pays the bills first!! :D

 

[Onestep]

get-lit are you planning on running a backlite on those screens? Is it going to be variable brightness too?

 

[get-lit]

Yes, will go with either a red or a white LED for the three buttons. Having variable brightness will depend on whether or not there will be enough com pins on the controller board after implementing the other functions.

 

[UNiT5]

Interesting

 

[langham]

Those look just like Nintendo DS screens. You think you could have used those?

 

[get-lit]

These are smaller, just for use with one thumb. Didn't want to go larger because I need to minimize the distance the handle is moved rearward so that it's closer to the center of gravity. Also, even though a large screen was "neat" at first, a large size got old for me. A size suited for the thumb is functionally ideal without venturing into overboard territory. Plus smaller is quite a bit stronger.

 

[LightSward]

Re: Superlights shoot-out 2011: The Short Arcs

Took some more beam shots last night. Again the cars came sneaking up. Maybe I'll leave it on for Halloween.

Beam up close...

From a bit further...

From down the road...

It puts a bright pin spot on the clouds surrounded by a bit of a flood.

Great light. Beautiful beam. Hopefully one of my new searchlights can have a nice thin beam like that, only starting at 72 inches in diameter, latest, (World's Biggest....).

 

[sven_m]

Getting back to this:

I can't imagine yet, how peak illuminance might depend on focal length.

get-lit's program yields such results. But I doubt that max-lux can depend on focal length.
I thought photos of the Maxabeam reflector could help.

So, what happened meanwhile?
I tried to take some photos of my Maxabeam with a fellow worker. Everything but easy to get decent pictures with a non-flashaholic :-)
He has a 200mm tele. It seemed impossible to get proper pictures in 50m distance. That sounds really odd, but I promise: you will agree if you try yourself.
So we tried 25m. Perhaps that's too short, but on the other hand there's no way to get detailed pictures from 100+m distance, anyway,
with a lens that a private person can afford.

The pictures were taken through a solar filter.

Sort of focused:

, and as addition: slightly out of focus (different speed, though):

The focal length of outer and inner part varies massively in this example,
- focal length at outer diameter: 118mm
- focal length near center: about 10mm

The 1st picture clearly shows: luminance can't depend significantly on focal length (at 25m).
The focal length above varies about a factor of more than 10, major effects must show up in such a picture.

On the other hand : if it's about percentage effects, then there's no way to judge about this based on such pictures.
PS: the dent below the center is real. Fortunately local only. The former owner managed to bend the mirror somehow, perhaps while swapping bulbs.

I thought about convincing another guy to try with his 400mm lens, but I won't follow that way.
I might get pictures at 50m distance, but possible shooting errors will dominate percentage effects.
One might argue that more than 100m are necessary...
The reflector is great for such experiments but the tininess of the source leads to great hassle when shooting.
I hadn't eppected this in advance.

I don't think that arguments or formulas are of help here. The stuff is too complicated to yield some "compelling logic".



I wondered what Ra might tell us about this, but he hasn't been here since oct. last year.
However, I actually found something from him about this topic from 2010, here:

Within the range of aviable lenses: For all lenses with the same diameter: The focus length does absolutely not affect throw!

(the topic was about lenses at first), a few posts later reflectors were covered as well:

The amount of lux that is receved by the object is only determined by the (apparent !!) diameter and surface brightness of the light-source (sun, torch, candle...)

To me, this strongly confirms the idea that focal length doesn't affect max-lux in any way. But get-lit might interpret this differently.

Perhaps when Ra (as professional optics engeineer) or another sufficiently experienced guy chimes in one day about this question, he might have an idea how to bring the topic further. I guess it needs to be an experiment which is easy to reproduce, yet yields precise results about the effects.

 

[get-lit]

The concept that long vs short FL does not affect Lux came from the lack of distance when making comparisons. At moderate relative distance, they will have about the same Lux. Short FL can actually produce more Lux at short relative distance. But the collimation ability (etendue) of long FL better retains Lux as great distance.

I've been consumed in gearing up for Summer with Spring cleaning and projects at work to pay the bills, but I did a fun little test a few weeks back and the results were about as I'd expected.

I placed an XM-L LED drop-in (without reflector) at the focal point of an Orion cassegrain telescope (huge focal length) and compared the output next to the same XM-L located at the focal point of a 3" FL reflector taped off to the same 5" diameter as the telescope. The 3" FL reflector produced a much brighter and much more visible beam as I pointed them around outside. Although the 3" FL reflector had a much much shorter focal length than the telescope, it had way more light gather to more than make up for the lessor collimation. The light from the telescope was a very dim perfectly round circle that didn't change diameter nor intensity as I panned across objects of various distances, at least the change was much too little to be able to discern from where I was. With this observation it was clear that the miniscule light gather of the super long focal length of the telescope greatly hindered it compared to the 3" FL reflector of the same diameter. The highly collimated but worthlessly dim telescope beam next to the very bright and throwy 3" FL beam was not even a fair comparison from that observation point.

I then aimed them about a mile to the end of the road, drove down and saw that the once powerful 3" FL beam had now fanned out to discernably nothing. The telescope beam was still just as dim and with about the same beam diameter as it was when 30 feet away, but at this distance it was now obviously much brighter than the 3" FL beam. Again it was not even a fair comparison, but this time in favor of the telescope.

For a given reflector diameter, choosing a focal length is essentially about what you need to get out of the light. The telescope light was powerful when viewed at great distance and absolutely worthless when observed from the telescope, and the 3" FL was powerful when observed from the reflector and absolutely worthless when viewed at great distance. The telescope has a focal length of 1540mm which is about 20x the focal length of the 3" FL reflector. That factor is plenty to differentiate the intended purpose of the light.

I will do some more thorough experiments after I can make some more time for myself, and after this project as well.

 

[Ceya!]

I have been behind the CPF curve. So any new update. Need to read at least 20 pages to catch up.

S/F,
CEYA!

 

[get-lit]

Good to hear from you Ceya. I'm still making the most of this summer after the long hard winter. Will be picking this up in the Fall.