Enderman, in your Lens calculator I see that for working area you take clear aperture.
At the same time I notice that in the inside the part of the lens that passes light is CA while on the outside - it’s the entire lens area.
I’d like to understand that better. Could you give some pointers on why is CA the correct value here?
Clear aperture is on the outside (curved) surface of the lens, not the plano side.
It is not 100% of the lens diameter due to manufacturing processes.
I have contacted optics manufacturers asking if it would be possible to have a lens where 100% of the diameter is aspherical for collimation, but the closest they can do is 95%.
The size of the entrance pupil to the lens on the LED side is smaller than the diameter * CA.
Subscribed! 
So…the outer portion of the lens collimates lights the same way as the center but does so with less precision.
If the goal was to produce the sharpest projection - it would be the best to black it out.
If the goal is to produce throw - leaving it normally is a better choice.
Also: collection angle does not actually depend on clear aperture but rather on back focal length, edge thickness and refraction index.
Am I right?
Yes, that is true.
Although now you made me think, since the LED is not a very small point source the outer portions of the lens may still contribute to total lux even if they don’t collimate perfectly.
Another thing to add to my list of stuff to test haha
Updated the calculators with some extra graphics to show the light boundaries (green dotted lines).
Also redid all the equations with easier to understand variables.
The LED diameter is now used directly in calculations, so if your LED is a square you will need to multiply the side length by root 2 to get the max divergence.
Also working on a hybrid reflector calculator which combines a lens+reflector, to make it easier to see what diameter and focal length is necessary to collect 100% of the spill from a standard forward-facing reflector.
Enderman, as you’re on the topic, could you please add this?
Can you explain me how Lumens do not affect throw in standard reflector calculator? Let’s say we have reflector and same LED at 20% output. So as with this calculator, at 100% output we have same range? Something is not right here.
No, in that case since you have the same LED, increasing from 20% to 100% output would increase lumens AND intensity, which is why you do get more range.
The case where you get more lumens but not more range is when you increase the area of the LED die.
For example if you have one led with 1mm^2 area and 1000lm vs an LED with 2mm^2 and 2000lm.
The second LED has double the lumens but will make a spot that is 2x bigger because of the larger die.
The intensity, lumens/mm^2, is the same though because 1000/1 = 1000 and 2000/2 = 1000
.
The throw distance depends on the intensity, not the lumens directly, but intensity depends on lumens+area so in a way they are linked.