Calculating estimated OTF lumens.

[extremescramble]

Hi.
If I have an accurate OTF lumen level (taken in a calibrated sphere) for a given amperage - can I divide one figure by the other to give a 'rough' guide as to the OTF lumen levels at differing amperage levels or is it not that simple 😳
Any help would be gratefully appreciated.
Thanks
Philip.

 

[ASheep]

I think your best bet would be to get the LED datasheet, which has a graph of output vs current. You could then scale your OTF reading using that graph. Datasheets for CREE products are on their websites, I've never looked into other LEDs.

Cheers,
Alex

 

[extremescramble]

Thanks Alex.
I will check out Cree's website for the information 😊

 

[LilKevin715]

I was curious as well when it comes to OTF percentage and decided to do some testing to find out. I've test both Maglites and Solarforce hosts and the OTF percentage will vary depending on the host/setup.

 

[TEEJ]

I was curious as well when it comes to OTF percentage and decided to do some testing to find out. I've test both Maglites and Solarforce hosts and the OTF percentage will vary depending on the host/setup.

LOL

Of course the OTF will vary, hence the reason for the need for the OTF instead of just the LED lumens, etc. The lens, the reflector, etc, all come into play.

 

[DIWdiver]

Another way to do it would be to get a cheap lux meter. Lux and lumens should be proportional, i.e. if 200 lm gives you 450 lux at 2m, then 900 lux at 2m means you must have 400 lm. It may not be perfect, but I bet it's closer than using a chart from the datasheet.

 

[TEEJ]

Another way to do it would be to get a cheap lux meter. Lux and lumens should be proportional, i.e. if 200 lm gives you 450 lux at 2m, then 900 lux at 2m means you must have 400 lm. It may not be perfect, but I bet it's closer than using a chart from the datasheet.

I'd go this route too...if its the same LED in the same flashlight just driven harder...the lux/lumen change should be 1:1

 

[extremescramble]

Thanks for everyone's help and advice 😊
Philip.