*****In need of a simple way , or please explain the math details.

Flashlight Modding and DIY Parts
1

Updated maybe easier to answer-

Hello fellows,
I have not been here in many moons so I hope you all are well.
As hinted in the subject line, I am terrible at math, I can build you a nice set of cabinets or fab a steel car fender for you, even make a decent spreadsheet, but math has never been my strongest skill set. I am 60+ years old now and learning more math is not happening for me at this point
I know many of you fine people on BLF appear to be relatives of Einstein and have provided graphs and calculations etc. for just about all of it related to throw and all that it entails, and that is much appreciated to say the least, but I , sad as it may be , do not understand 85 percent of it.
So all of that being said…
In relation to the “worlds most powerful flashlights” graph/ diagram by Enderman
I have a question…please help me to further understand the example below.

Below are numbers from my arbitrary input into a calculator online at Rapidtables.

I would simply like to know how these numbers relate to the Enderman graph.

If the

Illuminance in lux: = 100 Lx (Input)
Distance in feet
To lit surface : = 30 Ft (Input)

And the Answer
=Luminous intensity
result in candella : = 8361.2736 Cd (result)

Would the light source in this example rank on the enderman graph?
Would the cd result above need to be multiplied by another number to rank on the graph?
Eg. 10, 100, 1000 or some other number?
Any simple response is greatly appreciated, please no complex formulas ,as it will not forward my goal to understanding this idea.

Many thanks

2

I have updated the text in this post from earlier today. Great to hear your input
Please.

3

The formula isn’t complex. It’s just a simple multiplication and division problem.

Here is a guide: Guide: Measure throw and beam distance for your flashlights - in 3 steps

4

What’s a enderman graph?

5

OP is referring to this list of lights with the longest throw distances: Most Powerful Flashlights in the World (by throw distance)

6

Thanks for that link Hoop! very helpfull especially the info in the beam throw table at the bottom showing the scale up through cd, to kcd, to mcd, which was the missing link which enabled my understanding of the equations.

And to member -Xxo here is a link to the graph I am referring to ,posted by member Enderman Most Powerful Flashlights in the World (by throw distance)

I believe my other dilemma concerns the huge variance in measuring distances that some of the members of the community may have used when posting their end results for lux which kicks off the whole process for the correct ultimate answer to the
Cd,kcd,mcd end result equation and it’s final answer.
I know from my own personal experience with a quality light meter and full charge any one of my torches may give a different end result at different distances using the same chain of equations, so what to do about that, I don’t know, any suggestions appreciated?

Thanks very much

7

Thanks, i didn’t know what this was either.

You’ve already done the maths to arrive at 8361 candela.

Candela directly relates to the throw, more candela means more throw than less candela. (If you look at Enderman’s graph you can see that the lights with more candela (bottom axis) always have more throw distance than those with less (left axis).)

The lights in Enderman’s graphs measure in millions of candela, the light with the lowest figure has 2 million candela.

I have no input into the graphs but i don’t see 8361 candela being relevant on a graph which starts at 2,000,000.
You would need to multiply your figure by about 240 to match the lowest performing light there, and by over 6000 to be one of the highest performing.

8

What kind of distances are you talking about? It takes a certain amount of distance for the light from an optic to converge so if you measure too closely to the front of the torch, before the light has converged, you will get a lower reading than if you measure at a distance after the light has converged.
Once you’re past the point of convergance the readings should be similar.

The distances involved depend on the optic/LED setup but can be anywhere from centimetres for smaller optics to metres for larger.

As a demonstration of this, if you shine a ‘throwy’ light closely at a wall (at a low enough brightness to not be blinded by the reflected light) you will see a dark area in the centre of the beam that gets smaller and then disappears as you back the light away from the wall. This dark spot is a result of the light not yet converging. (There are likely more techinically accurate terms to describe this.)

If it’s not this then i can’t think what would cause the different measurements, assuming it’s not related to ambient light or reflections influencing the readings.

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Thank you for the responses Marc E

And I have some answers for those valid thoughts for you.
For starters, I have yet in my life seen a breakdown in one article or document where it has shown that …

1000 millicandella is equal to 1 candella
100,000 candella is equal to 100kcd
1,000,000 candella is equal to 1 mcd

And as you can see there are two uses of the letter m, millicandella
And mcd for million candella ,this was one confusing point for me either from lack of study in this area or that I have never seen the above breakdown.
Also we are talking about light waves, electromagnetic energy and with some electronic components for example , resistors ,capacitors whose object is not to freely pass the energy but to slow it or not let it pass ,these are specified with
a “k “ ohms rating etc.
Basically at the risk of coming off as a really not so smart person, the only other time other than in electronics as stated above, I have ever seen the “k” used as a designation letter other than describing color temperature where it represents a kelvin, or unless ….you are talking about the kind of which —-example “Taylor Swift has 500k in her bathroom now to be used as facial wipes”,or k for 24 k gold
Which has nothing to with the number 1000 as far as I know.

The link above (response # 3 lepflashlight…by member -hoop) was what enabled me to put it together specifically the throw candella /distance chart at the lower portion of the article.

As far as your beam convergence info thank you, as I now believe the optics I have been working with converge somewhere beyond where I have been usually measuring (about 10 to 20 meters depending on variables at the time) so the light output has not reached its full spread as you have noted. I will need to change my distance to achieve a more accurate result for sure.
This also makes me wonder if all of the throwie light distance data being quoted all over the world is even close to 100 percent accurate?

Here is an current ad for a 60 inch sperry anti-aircraft searchlight, I and a friend owned one identical to this one in the late 80’s, Ours worked like a champ after some tweaking. If you scroll thru the comments below the article ,you go down a way and there you find discrepancy’s and links being quoted by previous owners of these searchlights as far as output and beam distance, which fits right in with possible questionable data on numbers that a person or company may claim, I personally do not think any light excluding huge lasers and maybe a 5000 –10,000 w short arc. can outshine these monsters. https://barnfinds.com/1941-sperry-60-inch-antiaircraft-searchlight/

Thanks much for the help Marc E

P.s. yes , I know someone is going to mention milliamperes , what ever!
Edit —-Just found this write up an ancient abbreviations, quite interesting!

10

Part of your confusion is because not everybody always sticks to the rules. Maybe it is about not knowing, maybe it is about being sloppy, maybe it’s not in their spell check. The international agreement on the so-called prefixes is as follows:

Capitalization. SI prefixes for submultiples (smaller quantities or sub units) are formatted with all lowercase symbols while prefixes for multiples (larger quantities or whole units) use uppercase symbols with the exception of three: kilo (k), hecto (h) and deka (da).

Of which the last one is seldom used. In NL mainly to pester primary school pupils.

You’l find a link to the subject HERE.

Another thing that will cross your path is the use of upper/lower-case in units. It’s upper case if the unit is named after a person who has had mayor influence on the subject like (Alessandro) Volta, (André-Marie) Ampère, or (James) Watt.

So the correct representation for the capacity of a single cell is: x,xxx mAh.