BLF recoil über-thrower

Ah, that’s a pity…
Thanks for sharing.
And i bet you don’t even smoke either? :slight_smile:

You’re gonna make us jealous. :slight_smile:

@Lexel, is that spot from the lens just smaller or also much brighter?

the lens was 20cm from the LED
so overall brightness far less
and spot brightness better

both pictures use same camera settings
f2.8 1/40s ISO1600

Hah I wish, otherwise it will be a waste of $100 xd
Always good to experiment though and pass on information to others who want to try similar stuff.

Could this be the good news we’re waiting for ??

Say 4 inch diameter and deep enough to collimate 120° of the emitted light?
That would be totally awesome.

Before random ordering a reflector size/focal length, we first must establish what ‘catch angle’ is optimal for a recoil reflector, and my suspicion is that 120 degrees is too much. My fear: the outer part of the reflector will produce a larger and fuzzier image of the die and therefore hardly contribute to the throw. As well as Lexel I will experiment with the cigarette lighter reflector to see if I find the same as with the Mirascope reflector.

I’m not trying to dissuade anyone from building a recoil reflector light, but it seems some are overestimating the improvement in light collection efficiency of a recoil setup over a traditional reflector setup. A typical traditional reflector (like a C8 reflector) already collects 75% of the light emitted (lumens) from the LED, so collecting 100% of the light would only be a 33% improvement.

If you are trying to think about the total light collected by a reflector, the intensity vs angle plot (let’s call this angle theta) quoted above (from the giga thrower thread) doesn’t tell the whole story. This plot is a slice of the 3-dimensional beam profile. To get the total emitted light you have to consider this 3d shape. For example, the light is less intense at theta angles around 45 degrees, but there is actually a lot of total light in this region of theta angle because of the shape of the 3d beam; basically for the same reason a circle’s circumference gets larger as the diameter is increased. Mathematically, this means integrating around the other axis (the axis perpendicular to the LED surface). When you do this it adds a sin(theta) factor, so the total light emitted at different angles is now proportional to sin(theta)cos(theta). This is the multiplication of the intensity pattern (cos(theta)), which is greatest around 0 degrees, and sin(theta), which is greatest around 90 degrees. The result is a curve that peaks around 45 degrees.

We can get some number estimates by using wolfram alpha to integrate for us.

This integrates all of the light from 0 to 90 degrees (1.57 radians) and the answer is 0.5. This is just a proportionality factor that we’ll use to compare future calculations.

Now, a C8 reflector is ~38mm wide and ~33mm deep. It collects light greater than half angle ~30degrees (inverse tan(38/(2*33))), which is about 0.523rad.

integrate sin(x)cos(x) - Wolfram|Alphafrom.523+to+1.57
gives us ~0.375, or 75% of the total light.

“Random ordering” ?

Anyway, we should have a look at how much light is emitted to the various angles.
Do consider though that a ‘normal’ reflector thrower uses all of the wide angled light too, so apparently it’s worthwhile.

Funny the previous post used this image too:

As you can see, contrary to what previous post claims, it’s more like 75% spill with a regular set up.
In the picture you can vaguely see the yellow lines that show that a recoil set up turns everything into a beam.
I have stopped at about 145° for both reflectors because the LED does not produce much light any further.
Moreover, it’s usually greenish brown light that comes from the sides, as you all may recognise in the coronas of regular flashlights.
And maybe that’s why flashlights often have a centring gasket with a collar that shrouds the wide angled light.

Either way, a regular reflector spills some 65° of the most intense light.
According to the picture we could limit the recoil reflector to where it is 50% intensity (relative to 100% @ 0°), which happens to be around 60°, thus 120° in total.
Maybe 110° is best, reducing the diameter some more.

(edit) I was wrong, EasyB was right…

I was attempting to explain in my post why your reasoning is incorrect. For example, an aspheric lens light usually collects a ~30degree half angle when focused. With your reasoning, wouldn’t you expect the light collection to be good in aspheric lights? Well, it is not good because it only collects ~25% of the total light. Djozz’s measurements here support that; just 21% of the total light from the LED is in the beam when in focus mode.

But it is not incorrect.
Just look at the radiation diagram of an LED and than superimpose that on the picture in the OP, and compare that to the picture above.
The recoil set up will focus all of it, including the 65° a regular reflector simply spills,which happens to be about 66% of the emitted lumens (my guesstimate).

As I explained, that diagram doesn’t tell the whole story.

Let’s talk about the aspheric lens light. Why is the light collection so poor if it’s collecting the most intense light?

EasyB is 100% correct, I’m planning to add those functions to my reflector calculator soon.

Also with a parabolic reflector the outside of the mirror should not be creating a fuzzier image.
The ideal catch angle is 180 degrees for 100% light efficiency.
You can imagine it would collect the same 90 degrees as a smaller shallower reflector but if you keep extending the sides you will end up with a larger diameter reflector but 180 degree capture.

The problem is that the focal length gets shorter the more degrees of capture you try to cram into something tiny like 4 inches, and that is what will increase dispersion and “fuzzyness”
But if the focal length is too long, you will get a really light beam and low light efficiency.

Yesterday I was looking for other mirrors, I tested with one I had at home which didn’t focus very well (weird shaped spot) but it still collimated the light as good as a lens.
This will only get about 60-90 degrees from in front of the light, but I think it would work well

We’re not discussing an aspheric lens here.
I think you don’t understand the radiation diagram.

His conclusion is not correct.
What’s so hard to get from that radiation diagram?
Just look at the surface area of the circle.
Only about 33% is green i.e. reflected with a regular reflector, whereas a recoil set up practically uses all of it, and when limited to 120° it still is almost 90%.
That’s nearly 3 times more light focussed / collimated for the recoil compared to the regular set up.

Why do you think i’m so enthusiastic about a recoil thrower?
LEDs are practically made for it.

It’s clear you have not considered what I wrote in my post above (regarding how the radiation diagram does not tell the whole story) and so this discussion is just us repeating ourselves.

And here’s the evidence again:

It seems to be about 2.5 times brighter (my guesstimate) than a regular reflector, and this is with a bad parabola for the recoil.

…for this,some guys used wavien collars,so as to collect much more light,but it is not possible now,because those collars are not available now.

You use terms i’m unfamiliar with, so it’s kind of wasted on me.
However, there’s not much more to the radiation diagram than what it shows us.
(edit) ehrmm… there is… sorry…(/edit)

Better to use a primary lens, but that complicates things and you can not zoom out to such a wide flood anymore.