Questions about Lumens

A while back (about 2 years maybe) I baught a SKY RAY S-R5. I was just looking to get a compact high power flashlight. I knew nothing of the underworld of lumaholics and moding flashlight. Recently I found this forum on accident. When I baught the light I was prommised 1000 lumens at a cost of about 30 bucks shipped. I recently looked it up and found I had paid almost twice what I could get the light else where and the other site clamed it only had about 230 lumens which is much more believable when compared next to one of my LED 3D mag lights.

Did they use chinese lumens to rate this flashlight?? :open_mouth:

Are there different lumens ratings like an actual use versus “hypothetical ability” that is used to sell the lights?

What machine is used to rate the lumens output of a flashlight and what is the correct way to measure lumens?

Where can I find an inexpensive device to measure the lumens output?

An integration sphere is used to rate lumens and they aren’t affordable for the individual although some people make home built versions to try to approximate this.

A lumen is a lumen :slight_smile: however the most exaggerated claims are usually based on the LED manufacturers max spec when fully driven.

Using that same number for a LED that is the highest bin and that isn’t fully driven is just totally misleading. The is also the concept of OTF (out the front) lumens which takes into account all of the losses inherent in a flashlight due to driver inefficiencies, reflectors, glass lenses, etc.

I don’t know anything specifically about the Skyray light you mentioned.

I just looked up your light. The 1000 lumen figure isn’t based on anything. In other works it’s just pure BS.

A single XP-G light will be in the 300 lumen range if everything is optimal. If I’m mistaken and your model has 3 XP-G’s in there then maybe.

I’m on lunch so I won’t be able to respond right away to anything else sent. But it has a single LED in it. I’m not even sure what make or model but it is a single. I’ve pulled it apart and it has a black adhesive tape over the board around the LED so I can’t even tell what brand it is from that.

R5 is part of the model name. My version of the same S-R5 model has an XML T6 and it was about $18 without batt & charger, I think it was $23 with.

wesco - We can estimate the lumens by identifying the LED and measuring draw in Amps with many inexpensive multimeters with some decent wire thickness using this source . If the light is a T6 XML and draws 1.5A it probably close to 550 lumens.

The battery used may have something to do with the draw. On mine, the UF batts couldn’t keep up with the LEDs demand for power, probably due to lower resistance of the body. I’ve got that drop-in in my SF L2 now and it is my brightest oem “bulb” using the original battery that had problems in the SunRay. I still don’t have a good, high draw batt, so I don’t know how good it might be in the lower resistance body. (That battery puts out 2.45A in my 2100 when fully charged and on turbo.) It’s pulling something over 2.2A now in the L2, but I suspect it will do a bit better in the SR after I get a Panasonic or Sanyo that will draw 5+A and not be a bottleneck to the driver/LED.

Hi, Wesco…

You got your first lesson in lumens—and blatant Chinese dishonesty. The Chinese figured out the lumen buzz some time back and have been mass-marketing their cheap electronics with exaggerated claims. When you see those “1400 LUMENS” and such on adverts, believe not a word of it. Manufacturers will commonly make up right out of thin air measurements to sell the lights.

Personally, I have never liked the R5s. A good Q5 XR-E is much more useful while being about as bright when driven harder. Read around this forum and you’ll find the real powerhouses we love and enjoy. Get yourself a Keygos KE-5 (I can recommend an ebay buyer) with a 2600 unprotected Sanyo from and charger and you’ll see a right-at-800-lumen powerhouse.

As far as luminosity, no need to spend money on an integrating sphere. Just follow the luminous flux charts on what each emitter will put out at the appropriate amps. Then subtract for losses to get a good out-the-front idea ballpark of what a light is producing. You’ll catch on.

Haha, yeah, it’s not like the grit system. There’s only one version of lumens…lumens. They are just overstating it to make it seem better than competitors who actually truly state the lumens of the flashlight. On ebay, any of those sub $10 lights are said to be 300 lumens, yet in reality, NONE of them are more than 100, most are 30-70. I bought my sipik sk68 off ebay for $5 and it just said something like “300 lumen led flashlight mini”, when it’s around 60 lumens!

Most people don’t realize that you are most likely getting only 70% of your emitter lumens Out The Front. You gotta pay the gods of optical friction their due, and cheap optics eat photons like candy.

Also, the driver/switch/wiring is probably eating another 15+% of the tail cap current (more accurately power) before it even gets to the emitter.

Yes, just like an internal combustion engine, lights aren’t 100% efficient in moving/converting energy, and they never will be!

Then I should be good at this… I am an optical god… Thats what I build every day. OPTICS!!! :bigsmile:

True story.

I could litterally make an entire sub business making quality parabolic mirrors for flashlights. With 90+% reflectivety… but no one could afford them I don’t think.

Wesco, GottaZoom basically answered your question but to answer it specifically the advertised 1000 lumen figure for the XM-L is about what the LED manufacturer lists as max spec and max current which would be 3A for that emitter.

The flashlight manufacturer is just repeating that info however they are not (it seems) driving it that hard so the reality is about half of that number before you even figure in the other inefficiencies.

There is logic to the numbers they use in many cases but it’s just faulty logic (or ignorance).

You guys have been awesome. That pretty much answers my questions and makes me even more certain that I’m not half bat s* crazy… Then again maybe I am… idk :bigsmile:

Thanks for the help guys

You can measure light output inexpensively with a lux meter (~20:money_mouth_face:. You can estimate total brightness (ie lumens) from this by bouncing the light off the ceiling and measuring the general reflection(s) with the meter. An “integration sphere” is simply an idealized version of this with a mirrored interior. To get an actual lumens number you need to compared to a light with know lumen brightness.

AH HA!!! Lol so my 3D mag light that states the lumens on the package (which i tend to believe more because there is clearly no chinese lumens count of 5,000,000,000, the number they put out is a lot more reasonable/honest) would be my constant by which I calibrate and guage the results of the other flashlights.

Lol I do this at work with a very cheaply made palm sized microscope. It has a zoom function but the numbers don’t really match up. So we zoom in until its focused on the imperfection in the glass and take a picture then we use the same magnification to measure our constant. In this case its an old lens for a loupe that has millimeters broken down to tenths. Using that picture we figure out exactly what the magnification is by measureing the 1mm span and reajusting the magnification until it reads out properly. Then we can measure our scratch and determine the exact size of the scratch. Its kind of rigged and not high tech but it works and its fairly reliable.

Now… Do you have any sugestions as to which brand is better??

Maglites are not necessarily accurate because they use the voltage from the batteries directly and that varies with the battery type and remaining power/level (so dimmer as the batteries drain). Most folks these days calibrate to a (better brand) LED light with regulated constant output as measured by others.

Cheap meters are pretty similar. I just got mine off ebay and it works fine. also sells a couple. This is the model I have and I chose it because the head area is smaller than most (so more accurate just in case I need to measure a precise spot). A larger head (really just a plastic dome which spreads the light above the actual sensor) allows you to be slightly lazier about exactly where you place it since the diffuser averages out over that larger head area.

Note not all meter are the same since it’s measuring across a spectrum and each meter can weigh each frequency within that spectrum differently. Ideally they approximate how the human eye see light and the measurement correlates with how humans perceive brightness.

There’s really no “best” cheap meter that anyone’s been able to determine, so might as well try that one above first.

Should be 84 on a standard battery.

Don't forget this thread from Match for referencing Lumens at different currents. Bookmark it!