I got the TK15 today and compared it to the VG10S. After about 20 minutes staring at the wall trying to decide what I’m looking at, I got fed up and thought that maybe I’m better off with a light meter.
Here is my problem. I do NOT like a hot spot on an EDC. The more floodier, the better. What I was looking at with the two flashlights I was testing was……one had a hot spot and little spill, the other APPEARED to have a weaker hot spot and more light in the spill. So I’m starring at the wall (like a fool) trying to decide if I was seeing “more” light in the spill or it was an optical illusion. Back and forth….
So…why not measure it?
Here is my question….are cheap light meters good enough that I can make comparisons between the lights? Or is it like my infrared thermometer that gives me 2-3 degree difference depending on the moon phase. It’s not going to help me if it says 400 lumens one days and 350 the next. Particularly comparing flashlights with very similar outputs.
My “plan” is to mark the wall with consecutive rings, define a certain location from where I will test all the lights and then measure the light output per diameter. Then I’m going to torture BLF with pictures, stats and my opinion.
If you want candela (throw), the meter above fits the bill well. But throw will only measure the hottest part of the hot spot, not the overall output.
A sphere will measure overall output by integrating all the light to the meter. (more fair for floody lights)
I measure “rings” with a yardstick on my “beamshot wall”. At 10’ it gives an idea what area it’ll cover in the real world. The oslon white flat gives a little 4” square, and a nice op-reflectored s2+ gives a nice big, soft hotspot bigger than the yardstick. But the diameter gives you the focus of the light, not brightness. This is more of a subjective measure of preference. I have measured lights with a larger ring that are way less powerful than others. Some with a smaller spot are way more powerful than others. It’s not really accurate to use your judgement to compare lights this way.
Be sure to measure what you want to measure. TBH there is either throw or lumens. Each has a very specific, measurable number that can be translated universally. Hot spot diameter, not so much, but you are on the right track.
I built a 17” “spherical” sphere to measure lights. Followed the “match’s mod” and tweaked a little. I have tubes, but wanted to fit the GT in the opening (sphere is a little more flexible on inlet diameter) and also be a little more orthodox in my methodology. The tubes are considerably more simple to construct and/or buy and do 99% of the same thing and with less math (multipliers and such).
edit: other two posts deleted, ??, but I use a dr. meter lx1330b in my sphere and a hs1010a for throw measured at a specific distance from the emitter. Both are decent meters under $50, but a sphere (or tube) is needed for lumen readings.
I thought that a light meter would give me X amount of light (lux?) on Y spot on the wall. The measure it out every 6 inches or whatever lands up being a good number. The rinse and repeat with the next flashlight.
For me, it’s the difference between the flashlight, OR the mods I do that make the difference. I’m not looking to get precise overall lumen figures, I’m looking at a way to compare the beam on t he wall from one light to another.
It will go to answer….
Is this flashlight giving a hotter hot spot and very little spill. Or is that flashlight giving me less hot spot and more spill? Or is the spill the same?
I want less hot spot and more light in the spill so as to be able to see more of the periphery and reduce the on/off that accompanies walking along with a flashlight that has a very tight hot spot.
Again for me, it’s not just about the lumens, but how are they spread out to make the flashlight usable.
Think of it like a garden hose with an adjustable spout. You can put out the same amount of water in a small or large area. If you’re washing your car and there’s a pesky spot of bird poop or something, a smaller stream might be more effective than a “shower of water” to get it off. But, if you had a hose that was 12” in diameter and a showerhead-type nozzle, you could dump gallons of water, per second, but it might not be intense enough to get the bird poop.
Well, an ultra high lumen flooder is the 12” hose spraying a rainstorm. Thousands of lumens spread over a large area, but no one area that is ultra-concentrated and intense. A high throw light, can have far lower throughput, but over a way smaller area. Like a pressure washer, with the pinpoint nozzle, putting out a half-gallon per minute, but can cut stone with the stream the tiny nozzle makes. Intensity is massive, but over a small area.
A meter, alone, will measure the pressure washer’s peak intensity of pressure at a single point. A sphere will measure the sheer volume of water (light) you can put out, since it integrates every droplet (photon) into the meter, where the meter alone can only measure what it “sees” from a single point of light on itself.
For a really rough measurement of the total light emitted by your lights you can use the “integrating bathroom” approach. Place light on top of toilet seat and point it face-up so the beam hits the ceiling. Hold your meter in your hand with the sensor below the level of your lights facing the floor. The only light that hits the meter should be indirect light that is bounced around your bathroom. The direct beam from your light should not be shining on your meter’s light sensor. Do that for both your lights and you should have a very rough idea of which is emitting more light (lumens). It won’t be at all accurate measuring exact lumens without something to use to calibrate your integrating bathroom. But even uncalibrated it should be just fine for comparing 2 lights to see which is brighter.
Measuring to see which light has more throw (lux) is much easier. Just set your light a fixed distance from the meter and shine the hotspot directly onto the light sensor. Do that for each light. The one with the higher number throws better.
Logically, that will also apply as you get away from the center.
Example….20 feet away, I have a 10 foot wide beam on the wall. Center is X, 6 inches out it’s X-, another 6 inches it’s X—….and on and on.
If so….I does need myself a decent meter!
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Edit……one of the things I “surmise” is that a cooler hot spot and more spill will let me keep more of my night vision. So in the end, I may lose some lumens and distance, but I will be able to see my surroundings better. What I don’t know is if it’s more of a theory or fact. Or if it’s only true if we are talking big lumens. For example, not much night vision left for several minutes when the Q8 goes off.
just my 2 cents , but I feel maybe you are getting too technical with how many lumens is in the spill and all.
If you are going to get a light to use outdoors and you are wanting it for say 15 feet to 100 meters for example (testing low through High or Turbo) , the amount of light in the spill area indoors at 10 feet from the wall will have absolutely no bearing on what you will see in real world use in my thinking.
I just grab 2 or 3 lights , walk outside and pick an area or 2 and shine them one against the other then make my decision which I like best in the environment that I will be using the lights.
Of course if you are talking up close work with something like a headlamp then the testing should be done up close.
I tend to agree. If a certain light looks better and feels better (and has a better UI to boot) I’ll be damned with whatever lux numbers I get at whatever distance from the hotspot.
However if I were auditioning different optics for a light, maybe… but I don’t need to do that either, because the optics manufacturers have already done that for us. Maybe if there was a specific LED not tested by the manufacturer, but usually I can find a LED they tested with enough similarities to make a judgment as to what it will do with said optic.
That said, I also own a Dr. Meter LX 1330B like many here. Under $50 and works.
About the question of the OP: almost all cheap luxmeters that I have, have a good repeatability of the measurements: what you measure one day will measure the same the next day. Also they have good linearity: if the brightness goes up 10 times, the reading will go up 10 times.
The way they differ from (very!) expensive luxmeters is that they error in different light colours: the most obvious and common error is that while neutral tints can be close to correct, cool whites are often read too high, up to 20% for over 7000K.
If the light colours of the flashlights that you measure are not too far apart, and if the goal is comparisons and not absolute correct lux values, just get a cheap luxmeter like the one recommended, and the accuracy of your comparisons are already way better than what your eyes can achieve.
