I am sure this is the right method of calculate the beam angle of a given dive light

[minos2014]

Hi, Guys. I think this is a nice place for me to ask you some questions, I am a kind of flashlight addict. Some of professional players always ask me How much beam angle of your flashlight, And i calculater the beam angle in the below three steps normally. I wish Mr.Selfbult can help me confirm if is right.
1. Measure the 3 parameters.

2.When you got 2 parametes, Now is a simple mathmatical problem.

3.Check the inverse trigonometric function table , You can get your beam angle is about 4 degree.

You guys has any other good ways ?Many thinks

 

[miketsp]

That's fine but don't forget if you're discussing a dive light you need to do this underwater because of refraction when the beam leaves the light.

 

[minos2014]

Thanks very much for your confirmation. Many think . Do you think the beam angle is very important for a dive light ?

 

[NAM001]

minos

your method of determining beam width looks sound to me. you may want to note the width as being the hot spot not the overall width.

 

[KeithG]

Not sure why you really care so much, but your algorithm appears to be flawed.

You appear to be measuring the outside diameter of the flashlight head. So if my flashlight has a rubber guard around it, that will change the end result. Or a thick body outside of the reflector. Neither of these packaging issues affects the beam.

Assume a point source of ligh originating at the light source. Or measure the bulb / led diameter. Ignore the size of the flashlight head. It is just packaging.

 

[NAM001]

after a second look i have to agree with giffenk. use the distance from the wall and the width of the hot spot. you wopuld use 200 cm adn 16 cm for the angle and multiply it by 2 or just use 200 cm and 32 cm and it will bel close enough. you have oposite and adjacent so the arc tangent woudl be calculated. i get 9.2 degrees with one method and 9.1 with the other method. you have a 9 degree beam. you will get much better numbers at about 20 ft or better.

 

[minos2014]

minos

your method of determining beam width looks sound to me. you may want to note the width as being the hot spot not the overall width.

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Yes . You are correct , Is the width of hot spot, Not the width of Overalll width . How much of the light angles of your light ? You like narrow beam or wide beam angle ?

---------- Post added May 11th, 2014 at 11:19 PM ----------

Not sure why you really care so much, but your algorithm appears to be flawed.

You appear to be measuring the outside diameter of the flashlight head. So if my flashlight has a rubber guard around it, that will change the end result. Or a thick body outside of the reflector. Neither of these packaging issues affects the beam.

Assume a point source of ligh originating at the light source. Or measure the bulb / led diameter. Ignore the size of the flashlight head. It is just packaging.

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Yes, Giffenk
Your method are much more precise,Thanks very much for your reviews . You know why so much players like narrow beam light ?

 

[lowviz]

...//... You know why so much players like narrow beam light ?

Easier to signal with a spot (narrow beam)

Easier to see with a flood (wide beam)

 

[minos2014]

Easier to signal with a spot (narrow beam)

Easier to see with a flood (wide beam)

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You are correct. Lowviz . and for narrow beam it is much better in water with poor visibility .

---------- Post added May 12th, 2014 at 01:27 AM ----------

you will get much better numbers at about 20 ft or better.[/QUOTE]
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Yes . You are right . i agree with you . I just want to know how big the beam angle is most popular in the market ?

 

[NAM001]

I dont remember but it is probably 4-6 degree. I think you will get a smaller beam if you back up sayto 10-20 ft and make your measurements of hte hot spot.

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Yes . You are correct , Is the width of hot spot, Not the width of Overalll width . How much of the light angles of your light ? You like narrow beam or wide beam angle ?