Question About Throw Distances?

1jono · Nov 8, 2014

Hi All,

I have been wondering about the throw distances manufactures quote with their flashlights.
I always halve the quoted throw to give myself a more real world usable throw distance but after using a few of my lights I am beginning to think
that halving the distance is still being slightly over optimistic?

I understand that the light reaches the quoted distance at a specific lux reading but what lux reading or distance would be a more real world figure?

For instance Fenix claim 185m for their PD35 (850 lumen version) and selfbuilt measured 195m at .25 lux.Well both my PD35's struggle to light anything up that well at 100m or is my sight failing??

What do you guys think?

I know this can be quite subjective depending on how good someone's sight is Etc. but say enough light to make out reasonable detail with average sight?

twl · Nov 8, 2014

You pretty much can't see anything at .25 lux.
It's just a standard level that is used by the industry to show that some light gets there.
It's sort of like using the run time standard to gauge run time of your lights, when the standard allows run time to be claimed until the light runs down to 10%.
Neither of these things is anywhere near useful in real life.

I recommend figuring out your own "rule", such as 1 lux on target, or something else that suits your needs for real life.
Same with run time. Run time to 50% used to be the commonly used figure.

Timothybil · Nov 8, 2014

A member in another thread suggested dividing the throw numbers by three, or for those of us uncultured barbarians on this side of the pond, when you see meters think feet.
I know that I have tested several of my throwers by seeing how far away I could recognize an object, then measuring that distance, usually with Google Earth. My results pretty much bear out his suggestion.
As far as run time goes, if one looks at the charts Selfbuilt and HKJ do for their reviews there is usually a sharp drop off at the end of the run. I normally just subtract about 10 or 15% from the stated times and use that as a more reasonable figure.

1jono · Nov 9, 2014

Thanks for the replies.
Ha,I like it,meters think feet.We're the same in the Uk,well people of my age anyway,we still use feet,inches,gallons Etc.

I think dividing by three sounds like a good representation of a real world throw figure.
I'm going to use that and test it out.
I wonder if 1 lux on target would equate to dividing the stated throw by three,possibly.
Going to try your 10-15% off stated runtimes as well.
Do you mean off manufacture stated or self built stated?

Timothybil · Nov 9, 2014

What I was doing was using Selfbuilt's real as-tested numbers and applying them to manufacturers' claims. If you know the current draw of the LED in question (Like Lumens Factory drives their XP-Gs at 1 amp) one can get pretty accurate numbers from HKJ's cell charts, and of course the real numbers for the light Selfbuilt is testing.

mudcamper · Nov 9, 2014

.25 lux is moonlight, and it is quite a lot of light if your eyes are adjusted to the dark. It's plenty to see by, just not from hundreds of meters away, which is the rub.

Although it depends on conditions (fog, pollen, or clear air) and what you are trying to see. Some examples. My M25C2 which has an ANSI FL-1 rated 498 meter throw, I can actually see buildings and vehicles (glass and/or bright surfaces) at those distances. Animals in a field I cannot, unless of course they are looking at me, and then I can.

The numbers you see on packages today are likely to be ANSI FL-1 calculated numbers, which are useful for doing apples-to-apples comparisons of different lights against each other.

The beam distance is calculated from the measured candelas peak beam intensity using the inverse square. So take the candelas, divide by the brightness you want (in this case moonlight, so .25), and then take the square root.

There are lots of details on the FL-1 standard out on the net. Here is one.

1jono · Nov 9, 2014

Timothybil said:
What I was doing was using Selfbuilt's real as-tested numbers and applying them to manufacturers' claims. If you know the current draw of the LED in question (Like Lumens Factory drives their XP-Gs at 1 amp) one can get pretty accurate numbers from HKJ's cell charts, and of course the real numbers for the light Selfbuilt is testing.

Thanks for that,I will do some calculations as advised.

mudcamper said:
.25 lux is moonlight, and it is quite a lot of light if your eyes are adjusted to the dark. It's plenty to see by, just not from hundreds of meters away, which is the rub.

Although it depends on conditions (fog, pollen, or clear air) and what you are trying to see. Some examples. My M25C2 which has an ANSI FL-1 rated 498 meter throw, I can actually see buildings and vehicles (glass and/or bright surfaces) at those distances. Animals in a field I cannot, unless of course they are looking at me, and then I can.

The numbers you see on packages today are likely to be ANSI FL-1 calculated numbers, which are useful for doing apples-to-apples comparisons of different lights against each other.

The beam distance is calculated from the measured candelas peak beam intensity using the inverse square. So take the candelas, divide by the brightness you want (in this case moonlight, so .25), and then take the square root.

There are lots of details on the FL-1 standard out on the net. Here is one.

Thanks,thats a good explanation.
And thanks for the link with information on ANSI.

Question About Throw Distances?

1jono

Newly Enlightened

twl

Flashlight Enthusiast

Timothybil

Flashlight Enthusiast

1jono

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Timothybil

Flashlight Enthusiast

mudcamper

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1jono

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