The BLF GT reflectors measurements might be interesting for some people to play around with:
Diameter: 118mm
center hole diameter: 20.1mm
Max focal length: 11.5cm
Reflectivity: 90%
Cree XHP-35 HI diagonal: 2.9mm (2.5mm side length)
You’re welcome 
I will try to find it when I have time, it seems that I have deleted it from my desmos account so I can’t get it immediately.
That will be really difficult, more of a job for an advanced ray tracing program 
If you want to estimate stuff like that I suggest using this free software here: * OpticalRayTracer Home Page
Thanks, I will double check that everything is in mm and add labels for the units.
Do you know which one of the three imperial calculators you’re having the issues with?
Also, the way I calculated the max spot diameter is by taking the distance from the LED to the closest point on the reflector/lens (which is not equal to the focal point since there is a hole)
Then just using similar triangles, LED diameter / distance * 1km = spot diameter.
This is essentially the outer edge of the “corona”.
Keep in mind I am using the MAX spot diameter, so that means using the diagonal LED diameter, not the side length.
You cannot use lumens=lux/m^2 because the brightness is not uniform, the outer edge of the spot will be much dimmer than the inner part of the spot.
[quote=Enderman]
Reflector1
Ok, that first part is very nice. I hadn’t thought of that. So in my case it wouldn’t be 20mm (only for an ideal point source), but 20mm - sqrt(2 * 1.06mm^2)/2 = 19.25mm
Why don’t you implement both, outer edge corona and actual hotspot?
Just started playing with that, thanks.
I will echo what everyone else is saying: Subscribed! Thanks for sharing! This will be a very valuable resource!
Ah, I found the bug, thanks. The new links I post should be fixed.
It will take a lot more calculations to find the true hotspot, because I need to figure out exactly where the projected images of the LED are overlapping the most, at the same time taht the images are changing in shape, and also moving away from the center of the spot.
I’ll have to spend some time thinking about that one and see if I can find an equation that isn’t just brute-forcing the answer.
You’re welcome
Thank you!
No, the focal length of a parabola is the distance between the focal point and the vertex.
small f
The maxabeam uses a reflector with 10mm focal length.
A parabolic reflector does not have a fixed focal length (is is not a lens). That is why I call it “maximum focal length”. The longest possible distance. Thus, there is also a minimum focal length. It depends on the type of light source used. With an LED it is the horizontal distance between the led and reflector surface (calculated above in post 13). With a bulb (emits light in all directions) it is half of this value, so 10mm.
One always needs to account for differences between the theory and the reflectors and light sources we use in practise.
It doesn’t make sense to argue about the specific designations though. They don’t change how we calculate things.
I’m just going by what the datasheets of optics manufacturers say.
You can take the values from any one of their datasheets and plug them into the calculator and you will get a reflector that is exactly like the one they designed
I don’t see your point? I never wanted you to use the “maximum focal length” for the calulation of the reflector.
It is only needed for calculating the size of the actual hotspot in a specific distance.
Or are you talking about the problems I had before? I was trying to test the imperial calculator by inputting the measurements (converted from metric) of the Maxabeam reflector. I got a different result. It didn’t look right and the luminous flux values were off compared to the metric version.
I was talking about what you said about the focal length being in cm, which it is not, it is mm.
By the way, the focal length of a parabolic reflector is the distance between the focal point and the vertex, that is the definition.
https://www.google.ca/search?q=parabola+focal+distance
So 10mm for the maxabeam.
I also checked and the metric vs imperial versions of the calculators should give the exact same lumen/lux values when you convert your measurements form mm to inches.
Ok, yes, I see it works. Sorry for being confusing. I never use the actual focal length for anything so I didn’t think you might need it. I was inputting the wrong number. The metric and imperial reflector1 variants work nicely this way.
BTW: the imperial version still has some metric input boxes and calculates the reflector size in square millimeter. 
How about luminance in cd/inch^2? 
I still think calculating the actual hotspot size (the smalles possible spot) makes sense. That is what we measure with lux meters. That is what people want to know.
Can’t we just do it with the standard parabola equation? Please note that these are for an upright parabola centered on the y-axis. Yours is rotated 90 degress so you would need to switch the x and y designations.
We take half of the reflectors diameter, c/2, as the x-coordinate of the reflector point which is farthest away.
We then use the parabola equation y=((c/2)^2) / 4f to get the y-cordinate (f being the real focal length). So know we have the coordinates of a point on the rim of the reflector.
Now we just need the coordinates of the corner of the LED. That would be x=(sqrt(2*(s^2)))/2 and y=f.
So now we have two points and we can just calculate the distance between them.
dfmax = sqrt(((x2-x1)^2)+((y2-y1)^2))
dfmax is what I have been calling “max focal length”.
This allows us to calculate the actual “minimum” hotspot diameter:
dhot = diameter_of_LED * distance_to_hotspot / dfmax
(This last calculation might require converting some of the units)
Yeah the imperial version still calculates mm^2 of the reflector because the standard way to measure intensity is cd/mm^2.
Since you don’t have to care about the area of the reflector, it’s just an intermediate value in the calculation, I left it as mm^2.
The problem with the “inner hotspot” is that for the type-2 reflector the shape of the reflected LED is getting smaller and smaller as you approach 90 degrees (the edge of the reflector) causing a “ring” of light that is not going to the center.
The farther off angle that the lens/reflector is from the LED, the more “skewed” the image is.
If you look at an LED from 45 degrees, it looks like a trapezoid.
If you look at it from 180 degrees, it looks like a line.
Also, it doesn’t matter if the parabola is vertical or horizontal, you can literally just switch the x and y in your equation to turn it sideways.
Well it’s not a “standard” calculator 
. Somebody who thinks in inches probably doesn’t have a feel for square millimeters. Personally I think the imperial version is not needed at all, but then again I’m not from the US.
You don’t have to do it for both. You can just add it to reflector1 which is what 99.9% of lights have.
Yeah, that’s why I mentioned that.
Yeah I’ll do that.
The reason I made a metric version was because I originally had only made an imperial version, because both optiforms and phoenix have all their reflector specs in inches.
For people who plan to order reflectors from them it is really easy to take the values straight from the data sheet and put them in without having to convert to mm
I guess I could have also built in a “mm or inches” option into the calculator to choose between the two. Maybe in a future update.
WOW. Great tools you've developed here, very interesting stuff! :THUMBS:
Thanks for putting such time and effort into all of this, I know it is appreciated and will be put to good use :)
-Ben
Thank you
I have also started to play around with the lens calculator. Have you thought about how the Wavien collar impacts otf Lumens? sma calculated here is collects 75% of the light and 25% goes through the hole. Since you assume 2.19x the luminance using the collar, the lumens coming out of the hole would be 2.19 x 25% = 54.75% of the LED lumens. After this you would multiply, as before, with the lens transmission rate to get otf lumens.
Yes, the OTF lumens also takes into account whether the wavien collar is on or not.
The only thing is that I do not set the limit for emission angle for when the wavien collar is activated, so if the green lines are going through the collar then that will give incorrect numbers.