Help with candelas for different emitters

LED Flashlights – General Info
1

Hi all,
I'm going to buy a c8 and need help for choosing the emitter.
I'd like to get some luminous intensity numbers for the following leds that seems common for this host.

@2A [lm - kcd] @4A [lm - kcd] @5A [lm - kcd] @6A [lm - kcd] @8A [lm - kcd]
XPL-HI 800 1350 1650
XML2 900 1500 1900 2100

XHP50.2 (half current)

 1000 1800 2500 3100

SST20

 500 750 850

SST40

 900 - 40? 1600 - 70? - 80 2000 - 85? 2200 - 95?

SFT40

 900 1600 1640 - 160 2300 - 250

CSLNM1

 600 850 - 230 800

CSLPM1

 700 1150 1400 1500

CULPM1

 - 235

The lumens are from some measurements charts, rounded for lazyness.

I found a similar thread but almost no response, maybe I'm lucky and I'll get some help :)

Thanks

2

This is great timing. I just did some candela testing last night on my C8+’s.

For CSLNM1 I got 230KCD at 5A. I haven’t lumen tested that one yet.

For SFT40 I got 160KCD and I believe the drive current to be 6A. It’s putting out 1640lm OTF.

3

Thank you :slight_smile: I added the @5A column to the table.
I’m wondering if it’s possible to estimate other amperage’s values for the same led, to fill a row having just 1 measurement of lumen and candelas

4

Quite easily using test results provided by other members of this forum. For example, here is an SST-40 test which provides a graph showing output vs current (early on in first post):

This thread also contains some of the info you’re after: SFT-40 vs CULPM1.TG vs YINDING 5050 30W in C8 reflector

Also i see you have ‘half current’ by the XHP50.2. Not sure what this means but the results look normal for the 3V version.

Also, it’s worth noting that whilst the CSL*M1/CUL*M1, SST-40, SFT40, and 3V XHP50.2 come in limited flavours with little difference between them the XP-L Hi, XM-L and SST-20 have different variants that have very different outputs. Especially the SST-20, as an example the 2700K is very different to the 6500K version so in these cases it’s worth clarifying which version you’re referring to. (After all, you don’t want to pick the SST-20 based on the 6500K figures and then get a much lower output by choosing the 2700K version.)

(Also, all figures will only be estimates due to LED tolerances, versions, differences in measuring equipment, driver and battery characterstics etc etc, but this is countered by the fact that the eye needs a fair amount of output difference to notice it. For example, unless doing a side by side comparison i doubt anyone will be able to see the difference between 800 and 900 lumens.)

5

I’ve already pulled the lumen values from the measurements threads, I’m asking if there’s a simple formula to calculate the candelas given the known c8 host and amperage/lumens.

Added to the table, thanks!

The measurements I found are relative to a 6v emitter so I reported half current values.

I’ve seen almost all throwers use 5000k to 6500k leds, but if someone can provide numbers for lower color temperatures it’s ok.
I’d just like to have an overview of macro differences in performance between these emitters so I don’t care about exact values. As you said it’s hard to tell the difference between 800 and 900 lumens without a measurement system or a reference.

6

Candela directly correlates to lumens. If the highest mode is 1000lm & 100kcd, then the same light making 250lm on a lower mode will make 25kcd. If you have the lumen output test chart and at least one candela measurement, you can calculate candela at all other levels.

7

Thank you tactical_grizzly, I thought it would be a crazy formula :smiley:

8

…for one emitter.

A smaller chip will typically give a tighter hotspot with more cd per lm, and v/v.