How to make the best single lens zoomie... (alternate title? we finally have a complete math model)



What the heck are you talking about?
I agreed with you that the two lenses together had half the focal length just like you said…
I also never claimed that only diameter matters, that was someone else.
Maybe you should stop being so condescending and actually read what other people post?

then i apologize and i mean it… then its directed at the other 90 percent that keep telling me made up laws that dont exist… my “believing” this made-up and fundamentally incorrect law? thet keeps getting passed around?

got me made fun of on a camera site… it made the telescope builders question my sanity… it simply does not exist…

take my apology to heart then.

but nothing changes my challenge, for anyone to support the non-existent law “diameter = throw”.

it simply does not exist… and this is a “site wide” misconception…

people keep comparing lenses, and every time i say “look at the one with the lowest f-number? everyone keeps chiming in, with poop advice… and its all based on lies.

i wasted a good year or two of my LIFE operating on this “fundamental comcept”? and wondered why i had such trouble understanding mor equations and optics laws to further my own work…

this law of “only diameter yields throw”? needs replaced… with…

“only the f-number matters, only a lower f-number yields throw”

okay, it wasnt you… accept my apologies, and we’ll get back to the more important business, when this is done…


sedstar: first I will say again that throw (defined as the luminous intensity of the beam, measured in candela) and light collection efficiency are two different things. I think you are are focusing on optimizing the light collection efficiency, which, while important, is not the same thing as throw. A light can have a lot of throw but have poor efficiency. For example a light with a large diameter lens and low NA.

Now, regarding whether the throw is proportional to the lens area. I will admit I can’t find any paper describing how to predict the throw of a flashlight. So I can only, again, refer to this thread. That Edmunds optics document seems to focus on light collection efficiency and does not talk about throw. But, again, throw and efficiency are different things.

what i AM saying is?

luminous intensity has no PLACE in the lens selection and construction of a single lens zoomie. none. isnt even a consideration…

what emitter or other light source you select? thats up to you. whether you use a waiven collar or not? again, thats up to you. the ONLY thing that matters? is that the f-number of the lens? “matches” or exceeds the “f-number” of the source…

since the source isnt a lens, that statement appears non-sensical? but when you replace the word “f-number of the LED” with the phrase “numerical aperture” of both the lens and the source? it makes more sense.

stated yet another way? the angle of emission, whatever it may be? must be matched with a single lens of at least that angle, and more if possible.

this critical ANGLE, that the led source is coming out at? you get that easily, from the datasheet… the critical angle of the LENS? isnt that obvious… the only easy way to see that angle? is to make a rough drawing to scale, of the diameter of the lens, and the focal length back to the point the 3 lines intersect? and either be careful in your drawing to SEE that critical acceptance angle of the lens, or, to calculate it, using the dimensions of the lens (FL, diameter) to arrive at the F=number that presents that critical angle. (chief soh-cah-toa)

each and every time i mention the F-number? someone “corrects me” and states that “no no, that lens there, the one with bigger diameter? only diameter yields throw”, and its 100 percent completely false.

i am stating, that if you know the angle of emission of your source? then you use whatever method of calculating the angle of the lens?? only then can you match them, or, god forbid exceed that critical angle. (lord forbid you collect more than the half angle, and collect 3/4ths of it, lol)

this isnt an “important consideration” amongst other considerations? its the only consideration. its basically ALL the edmunds optics paper concerns itself with.

you figure out the “f-number” of a lens, that matches or exceeds this critical angle? you are home free… if you cant find or exceed this critical angle?? you still have a chance at it, by selecting 2 large diameter lenses, and using the compound lens formula to yield you new resultant focal length… this new “lens”? will yield you a lower better f-number… to try to match or exceed that critical angle with.

matching this critical angle? is not important… its all there is. you IGNORE any thought of “diameter equals throw” because its a patent lie.


then? armed with this f-number? that you have to meet or beat? NOW you can select your focal length… which paints as large (floody) or as small (pencil thrower)… as you would enjoy.

i am stating, its not an important consideration? its the only condideration… nothing else exists.

I guess we can agree to disagree on this point.

heres why this knowledge is SO important?

because, we are going to CALCULATE the best “pre-collimator” lens, properly and perfectly chosen? to use with the ABSOLUTE best possible lens, that we can POSSIBLY use? as the focusing lens.

we are going to be able? to design, and then build? the perfect beast.

no other thrower, anywhere… from any company ever? is going to be able to beat it.

WE are all going to have this. Not any other flashlight site. Not a few fringe “engineering companies” that charge insane money for their kept-secret knowledge.

WE are all going to be able to have this? and know exactly how to build it and replicate it and tune it? a bunch of us… not some guy named “vinz” who isnt telling us “exactly how” to do it, because it affects his high standing reputation and bottom line as a builder.

“we” are going to then be “top dog”… “we” will know how to make the absolute highest meter-shocking thrower zoomie possible to make.

we’re picking this lock open… its going to be “our” greatest achievement… “we” are all going to be able to BUILD the best thrower in the world, and no one else is going to be able to touch it.

i built a precollimated light, that worked? twice… and only long and tedious “hand tuning” 4 lenses accomplished it… now i am “this close” to knowing exactly “why”.

we should be able to CALCULATE the exact best pre-collimator to place UNDER any given lens… likewise? given any best pre-collimator lens? we should be able to calculate the OPTIMUM forward focusing lens to put in front of it.

do you see my point of getting this all correct? what it leads to?

I guess we can agree to disagree on this point.

shrugs its a free world.

but i know this… edmunds optics engineers? thought this was SO important? they published a paper explaining it. not ONCE did “luminous intensity” so much as come up once.

all that mattered? was knowing the angle of the source… and how to calculate the angle of acceptance of the lens… “nothing” else entered into the calculations…

nothing else. you match or exceed those critical angles? thats all there is to it. they give two strategies of doing this? but, its the same basic design approach they use.

luminous intensity? is simply how many “moonbats” you later push thru the best chosen lens… its obvious you then want as many moonbats as you can MAKE, and all the regular questions of “best practice” come into play.

matching those angles or beating them? nothing else exists… nothing.

heres a perfect analogy?

a high-revving “short piston throw” engine? creates a LOT of horsepower? simply because it revs so high and so fast…

a TORQUE-y engine? with LONG throw piston? does not rev nearly as high, if it tried to? it explodes… BUT, the torque-y engine? CAN be mated with a tranny and rear end, that favors high speed, but accelerates a little soft…

the same torque-y engine could also be mated with a beefy “hauling transmission” and rear end… which will carry a heavy load. like a large hauling TRUCK, or, even a bulldozer.


when building big fast motors? which should you choose to build for? they have a saying… “build for torque… then the horsepower will just show up and be there”

this analogy applies here…

you nail your emission angle of your source? you match or exceed that critical angle with your lens? everything else falls into place. THEN you can pack all the luminous intensity into that critical angle, that you can… and the lens will collect all of it, and “throw” it as wide close in floody, or, as long of a pencil thrower as you LIKE…

but, its the only design consideration that means anything.

you nail your angle of emission? you meet or beat that angle of acceptance in the lens? THEN you can do whatever you want to increase the luminosity… then it will ALL go thru the lens…

as a design criteria? it makes perfect logical sense… thats why the engineers at edmunds opics needent concern themselves with luminous intensity. they obviously know about it… it doesnt matter.

you simply get the angle of emission, then you meet or beat that angle… its a secondary consideration how bright you can make the source be. job #1m the only job that matters? is to meert or beat that angle… the rest is just gravy and falls into place.

this design strategy? is ALL OVER the engineering world, in many different disciplines.

you want MORE WATER to make its way out your pump and pipe system? the widest pipe will ALWAYS carry the most water at top level flow. always.

after you get the biggest pipe you can? you can then worry about how big a pump you feed it with or can afford or hook up, or have enough electricity or horsepower to feed it.

top flow? will always be limited by the width of the pipe. always. no exceptions. everything else? is a secondary consideration you later make as best as you can…

our f-number of our lens? is simply the width of pipe.

in HVAC work? if you want to carry the most CFM possible thru a duct? you need the biggest duct possible… no other way in the end. if you use too small of a duct? you need to force feed it with too big and expensive of a fan system.

because you are trying to fit too many fat ladies thru the doorway, and its gumming up the works.

once again? the doorway needs to be as big as possible… later you select the biggest fan you can, based on what you have available. but if you want the most CFM out? your number one consideration is the width of the duct. period.

now, in our system? is not the f-number of the lens… the width of the pipe? the size of the duct? no wonder edmunds optics engineers, chose “numerical aperture” and matching or beating the emission/acceptance angle, as job number one, and really the only job.

after you have the biggest doorway? you can worry about how many fat ladies you can shove thru it per unit of whatever.

it makes… perfect logical design sense.

with guns? some people always want to throw a BIG heavy chunk of lead out, at the expense of slower speed… they think wider and heaver? is job number one.

other people? always want a smaller diameter projectile, lighter… moving obviously faster with the same amount of powder.

these two things are at odds withone another, just like lens diameter and focal length…

how to pick the best dance move? its actually sectional density… which is the relationship of diameter AND velocity, all balled up into one handy unit… the highest sectional density projectile? always has the best “drop tables” and the best “energy dump” and the best observed “killing power”.

lowest f-number? IS the highest sectional density…

the analogy holds once again.

its why the engineers at edmund optics only concerned themselves with it, to model the best illuminator system… its not an important consideration, its the only consideration that matters.

build the biggest doorway possible? you can later on worry how to throw more fat ladies or moonbats through that bigger doorway.

because once we get this firmly into our brains? all of our brains? when we then shift to the pre-collimator system… we get to PICK our “numerical aperture” virtually AT WILL… we get to specify the numeric aperture, out of thin air, by setting the ratio of focal lengths…

it looks to me? like we can set the f-number so low it will accept ANY emission angle we throw at it…

think about it… look at the equations… look at ALL that is there? basically “f number”… then imagine that we get to SET the f-number in the precollimation system? wherever we WANT to… we are obviously going to start at “completely ridiculous” and push it up (actually lower, lol) than anyone anywhere ever thought humanly possible…

our team? is going to throw a touchdown pass, each and everytime it touches the ball.

Sedstar, read it yesterday night before going to sleep, big mistake, sac02 says it perfectly, yet thanks really interesting and insightful
Time for a BLF zoomie :wink:

I contacted edmund optics, and they did confirm that a single aspheric lens with an appropriate surface equation would perform the same as two thinner aspheric lenses for collimation.
This makes sense, because if they are the same diameter and same (combined) focal distance, it shouldn’t matter if it’s a single or double lens system.
If you have a wavien collar reducing the light output tot 60 degrees full angle, in order to collect 100% of the light through the lens you need an F ratio of .866 because at 100mm diameter, the distance needs to be 86.6mm in order to have a half angle of 30 degrees.
This can be calculated using a right triangle: Right-Angled Triangle Calculator
Since the F number is constant, you can then choose whatever the maximum lens diameter you want for the light. Increasing the diameter will increase the focal distance (due to constant F number) and therefore the longer focal distance will lead to less divergence, hence better collimation.
Making the F number any larger will allow light to be wasted, while making the F number smaller will be wasting part of the lens.
TLDR: when using a wavien collar, the F number should be .866 for 100% of the light to be collected and no lens area be wasted.
Increasing the diameter = increasing the focal length = decrease divergence = increase throw.
We end up at the same situation of “how large of a lens do you want to fit in your flashlight” :stuck_out_tongue:
PS you are 100% right, ” F NUMBER is the measure of how much light a lens can transmit”, and with a wavien collar there is no reason to go above or below .866

If you look at camera lenses you see why F number counts

A 50 f5.6 lens has the same lumens like a
600mm f5.6 lens
The 600mm throws 144 times more and is about that much mor expensive and heavier

An F number without focal lengh says nothing about throw


How about structuring this whole thing?


#1: table of content, theorem, explanation basic theory of F etc.
#2: Problem with theorem X, and possible solution to problem
#4: Analogy of problem
#6: testing results, graphs, tables
#8: etc

The more you post, the easier people can see in your first post (table of content) what new things you have added, and what this thread is about… It’s just an idea…

Yup :slight_smile:

wavien collar there is no reason to go above or below .866

well, i mean, thats the HALFangle… lord forbid we try to be greedy and grab more than half the loaf of bread, LMAO…

but, in other news… now you see the holy grail value, of being able to “set” the numerical aperture (which is the f-number with a fake ID) where you WANT IT, by simply selecting the ratio of focal lengths? in the precollimator math model?

you SET your f-number wherever in the &^%$ you want it to BE…

i mean, talk about possibilities…lol

we get the f-number set low enough… you can shove as many moonbats as the emitter can MAKE thru that opening…

then theres… that lens…

looking like something along the lines of 100mm diameter… hes estimating in the one post, over 4.5 inches… closer to 5 inches?

calling an inch roughly 25mm… i get 125mm FL… in a 100mm lens… F 1.25…

but… two of them touching? F .625

which isnt TOO shabby, might work for date night in the barrio? LMAO…

(i took the liberty of starting a “lets see your coolest lenses” thread, ha ha… the boys are already starting to show off their toys they liked playing with… hee hee)

and someone with a highly figured and polishd customized MAG had a surplus shed coated aspheric looked interesting…

of course, 100mm lens? F=.625, thats a strong contender… the SINGLE lens had decent performance for him on his meter… was wondering about whacking the F number in half would do even better…

That’s the lens I used in my lightcanon, and the one I said I couldn’t beat with any other cheap lens.
I have three of them.