A Perfect Dedome?

Are you sure it applies to “throw”? Or intensity of illumination, regardless of angle?

“The candela (/kænˈdɛlə/ or /kænˈdiːlə/; symbol: cd) is the SI base unit of luminous intensity; that is, power emitted by a light source in a particular direction, weighted by the luminosity function (a standardized model of the sensitivity of the human eye to different wavelengths, also known as the luminous efficiency function[4][5]). A common candle emits light with a luminous intensity of roughly one candela. If emission in some directions is blocked by an opaque barrier, the emission would still be approximately one candela in the directions that are not obscured.

The word candela means candle in Latin, as well as in many modern languages.”

Wikipedia makes reference to blocking the light in some directions and letting it go in others, but does not implicitly refer to the direction as part of the meaning of the word, only that if the light is directed it is still the same power as if it’s left to radiate randomly.

Am I misunderstanding this? It does say that the light of one candle is referred to as one candela. I really never thought of a candle as having throw. Must be missing something. Again.

Honestly not trying to argue, would simply like to understand. It all gets confusing from candela to lumens. Difficult to understand where the “standard” is, if there is one. This means a lot to me as a photographer, trying to understand the concepts as they apply to taking a beamshot. I can make a Solitaire look like a TN-31 with my camera, but that doesn’t mean it’s so. My point is that I really need to understand the base concept so my beamshots will be reliable. Guess I need to send someone with a light meter out to a designated distance to take a reading on the amount of light hitting the meter at that distance, or more specifically have that person take the meter out until it registers 1 Lux, then get a reading on the distance. And here we go again, candela, lux, lumen, I’m lost.

Lumens = total light output
candela/lux = amount of light hitting something at a certain distance, also known as intensity.

I think I know where you’re misunderstanding. Are you saying that just because it reads a certain candela reading at 1 meter, it shouldn’t be the same at 10 meters because the beam will diverge?

Well, if that’s where you’re confused this is why for some super long throwers or even multi emitter lights we test it at longer distances to make sure that the beam is already fully converged and is starting to diverge. Eg. I can test my TN31 at 1 meter and get say 150kcd. But this is because at one meter there’s a noticeable ‘black spot’ in the center oft he hotspot because the beam hasn’t fully converged yet. Therefore, I should test it at a distance which is further than the distance it is at when it converges. This is why I (and many others) will test at 10 meters, and for my TN31 at 10 meters I get 3700 candela. Then I calculate it back to 1 meter, and using the inverse sqaure law I take the distance and square it, then multiply it by the reading giving me a total of 370kcd @ 1 meter.

Now with candles, you can measure it at 1, 10 or 100 meters it doesn’t matter. It doesn’t have a reflector and the light doesn’t have a hot spot, meaning the light is always diverging. This is why lights with reflectors need to be measured at a point which is after the beam diverges.

I’ll give another example. I can measure the throw of my Skyray King (3 emitters) at 0.5 meters and again at 5 meters (nobody actually measures this close, but it backs up the explanation). At 0.5 meters, the beam is probably at it’s convergence point or close to it, so if I calculated back to 1 meter, I get (I just measured this) 59kcd. However if I measure it at a longer distance, at 5 meters which is after the convergence point and I calculate it back to 1 meter I instead get 22kcd.

Not sure if I made it any clearer, but are you still confused?

EDIT:

Tom, is your 7G9 getting 120kcd stock? If so, something may be wrong with it, because it’s only supposed to get around 55kcd stock.

Well, NEMA, ANSI, along with all major manufacturers use lumens and candela and distance. Distance is directly calculated from candela - I certainly didn't make this stuff up, and certainly don't understand it all, far less than you I'm suspecting... If the industry adopted these as the standards, I think we should be using them. It's an industry adopted standard -- they are the only current standards - I see no reason to question them or come up with alternatives. People that know a lot more than me about light, and the technology behind it, came up with these standards.

It's the only way to compare -- this is why standards are adopted, that's what's it's all about, and it certainly comes in handy for us to compare stock lights, as well as seeing how effective mods are, if part of the goal of the mod is brightness and/or intensity.

I'm not paying the $67 to get the published standard, but based on the outline they made public, light output (lumens) and peak beam intensity (candela) are the two major measurements. I'm not saying my measurements are 100% right either, I'm just trying to do the best I can with what I got, and my methods and equipment seem to match up fairly well with what the FL-1 compliant manufacturers quote for their stock lights, and I know it's not perfect, and I know people have and always will question these methods.

The spec is all about flashlights, entitled "Flashlight Basic Performance Standard". I think this explains it: http://flashlightwiki.com/Light_Output_Measurements and here: http://flashlightwiki.com/ANSI-NEMA_FL-1.

I think I see how they’re deriving it, but I don’t see how it agrees with the definition of the word. But there’s a lot that I don’t get, so I won’t open that can o worms at this particular moment. Saved em, will dwell on em some, see what sinks in. :wink:

The light of a full moon huh? At what angle? Which season? From what latitude/longitude? Would that be a full moon that’s closest to Earth, or farthest away? With snow on the ground or without? Ah, standards are so…non-standard! lol

Perhaps I’m closer to getting more accurate beamshots. Perhaps I’m further way.

10 O’clock at night, no moon, very very dark outside. Couldn’t see a few feet ahead of me walking out there.

And zoomed in, by the light of my de-domed XM-L2 T6 at 3.82A in a HD2010

The trees on the back fence line are over 500 yds away.

The catch? 3200 ISO and 25 second shutter. I can make any light look dim, or any light look bright. This is what high end camera’s do. Which is why I need to understand the parameters of the standards. Sorry, didn’t mean to be argumentative.

DBCstm I don’t thinking anyone thinks you’re being argumentative, this is a discussion forum after all.

As for photos, I use ISO 400 and shutter speed 1/100. I find that it doesn’t really matter how bright it is, as long as you keep the settings the same and it’s dim enough to be able to compare all of them. In my thread here I could have made the shutter faster to prevent the TN31 from having that saturated hot spot, but then the SRK would be too dim. These photos were taken at roughly 50 yards (50 meters for everyone else).

I can’t take photos like yours because my (old 2nd hand) dslr doesn’t handle ISO800+ very well, so I have to compensate with longer exposure times if I’m taking actual beauty shots.

As long as there’s context or a basis for comparison I think it should be fine.

Flashlights in photos can only be compared with other lights taken by and identical camera with identical settings. However when we start to use candela, lux and lumens we can compare it very easily, because the numbers are standardised (albeit have a % margin of error due to variance among meters, but one can calibrate theirs if they have more than a few lights).

Sorry to jump in, but I think that, regardless of definitions, the way that most of us (well, me and some others) “measure throw” is by:

- Using a lux meter at ‘x’ meters

  • Taking the lux reading, then calculating:

That gives “a number” that should “theoretically” be consistent among readings from different folks.

I don’t know about the definitions, etc., but at least to me, that “number” is an “relative indication” of throw, i.e., if you get 120K with your light, and I get 30K with my light, your light “throws better” than mine, and we can all pretty much agree upon that.

The same goes when I’m modding my lights and if I’m interested in “how well does it throw after my mod?”. If I make a mod, and the number goes up by 100%, then the mod made the light a “better thrower”.

I have made some changes to a couple of lights lately, the HD2010 has very noticeable difference with it’s de-dome and the way I mounted the emitter. The M3 L2P took a jump, but then the de-dome and added chips don’t really seam to have made such a huge difference. This is why I’m confused taking the pics, I’m not seeing what I expected to see.

So I guess I need a meter to get some standardization going on to help me better understand what I’m seeing and then apply that to the photo’s.

By the way, those pics were taken with a point-n-shoot. Not just any point-n-shoot, the Canon G1X. My 5DMkII does much better even.

Thanks guys, appreciate the patience.

Even though I consider myself fairly new, I think that trying to judge throw “by eye” is really hard, because there are other factors that come into play. For example, I think that color/tint can affect how we perceive a light throws. Also, I think that, in another discussion, comfy pointed out that when you have a lot of spill, that can affect how you perceive throw.

Plus, we have variations in eyes/eyesight, e.g., my eyes suck, and I have terrible night vision. I have one light that measures about 66 Klux (my Jacob A60 dedomed XM-L) and one that measures 122 Klux (my shorty STL-V6 dedomed XM-L), both consistently. I also have a shorty DST with an MT-G2 (well, the same one, but before I dedomed it) and it was measuring something like 26 Klux.

When I take those outside in the dark, I could swear that the DST/MT-G2 is way brighter than the others, but they all look like they “throw” about the same at distance.

That kind of experience was what kind of pushed me to get a lux meter :)… along with “lessons” from Tom E, et al….

Just my opinion(s)…

What’s the G1X like? I need to replace my 400D.

I use this light meter. The sensor is tripod mountable and goes to 200klux (not that you’d really need it that high). It doesn’t come with a straight cable like in the pictures, but rather a long coiled cable which I think is better.

Usually I post pictures with a SRK or something common for people to compare to, and then I also post my lux readings as well.

Also to expand on what ohaya said, when compared on a white wall, I can barely tell my TN31 has more lux than the Shocker, because they’re both saturated. By having more flood it makes it harder to distinguish the beam or hot spot, which is why aspheric throwers are big ‘wow’ lights because they appear to throw far, when in reality they just have a straight beam which stands out from the darkness and is easy to distinguish.

That last point is a good idea, a kind of “benchmark”. I do the same thing now, using my HD2010, which I don’t mod. I use that as my calibration, to make sure that my meter and/or something else is not throwing my measurements off. I think that we should all do that, have some light that all or a lot of us have, unmodded, so that we can really compare apples-with-apples.

is on the slow side, doesn’t natively do great macro’s and is large for a “point-n-shoot” camera. That being said, it’s the smallest camera that has IQ comparable to a full frame sensor. I have a 1DsMkII and a 5DMkII, the G1X comes astonishingly close in image quality and does very well in low light. The articulating screen is a big plus as well.

That said, I’d recommend a look at the new S1 as well. DSLR camera that’s just a wee bit bigger than the G1X, and you can use the lenses you already have for your 400D.

I carry the G1X with a 250D close-up lens and spare battery in a hip bag, can’t do that with the bigger interchangeable lens camera’s.

Are you referring to the Fujifilm X-S1?
Do you own an S1? I just read a bit about it and people say it’s an all-in-one and an alternative to a DSLR. The 26x zoom looks pretty good on it.
I would mostly be using it for family photos, day and night time landscape photos and occasionally night time beam shots and macros.
All up this looks pretty good with the decent video recording, and the mega zoom + 1 cm macros., I’ll research this further. Thanks DBCstm :slight_smile:

Looking at it on Amazon @ $629 with that telephoto lens it does sound like a killer.

I was actually referring to Canon’s new Rebel SL1. It’s a mini DSLR that would use the lenses you already have and step up the image quality you’re used to with your 400D. No built in lens, you’d use the ones you already have or the kit lens.

The primary thing for taking beamshots is a Manual mode. For taking shots of kids you need a fast lens, be careful of built in zooms as they tend to slow down horribly when zooming and your shutter gets too slow for action.

The Canon G15 might also serve you well, it has a fast lens and does well in low light…also takes macro’s and is considerably cheaper than a G1X.

And now back to the regularly scheduled program….I saw a pretty significant tint shift in my XM-L2 T6 when I de-domed it, but the XM-L U2 didn’t drop so much, wonder why that is? The XM-L was pretty blue to begin with and it’s now just barely on the blue side of white, I really like it. The XM-L2 T6 was a NW to begin with and got considerably warmer, almost to the point that I want to correct it with Lee film but I don’t want to lose the output. How can I go about bringing the orange/yellow T6 back up towards white? Or is that possible?

I actually cut a cube of copper about 3/16” thick to stack the emitter on top of the copper star, reflowed them onto the star together then soldered the leads from underneath. I had to inset the pill deeper into the reflector as well, but now the problematic reflector is no longer close to the solder points and the de-domed XM-L2 sits up inside the reflector for a nice tight beam with a fairly decent spill. I can see a white barn lit up at 610 yards, but what the lux is way over there I have no idea. Looks bright enough over there to read a note by, but I can’t be for sure. Would be interesting to see what cd this light now has.

I’m thinking that the reason for what you saw is that it depends on the phosphor maybe, the thickness, etc. of the phosphor layer?

On the ‘Accidental MTG2 dedoming’ thread (Accidental MTG2 dedoming.), two people (myself included) noted that when the MT-G2 was dedomed, for us, the color/tint went cooler, rather than warmer, and we were both surprised.

A cooler MT-G2? Hmmmm……

I’ll check out the Rebel S1 thanks Dale.

As with the 2nd generation of Cree LEDs, not sure about the others, but XML2 and XPG2 seems to be really yellow after dedoming, even if it was CW 1A to begin with. Using the block to elevate the emitter was clever. Unfortunately there is no accurate way of determining candela by eye since your iris contracts and expands to let in less and more light respectively.

Yes, some (not so good) pic here: Accidental MTG2 dedoming..

But the aperture does not :wink:

Click on the pic and open it up in Flickr, then right click on it to see it original size. That barn is 610 yds away! The camera settings were chosen to represent what I was seeing, I was comparing 2 lights. The fence in the foreground is 100 yds from the light. The trees that appear in front of the barn are actually 320 yds from the camera while the barn is 610 yds.

Settings: 0.3 seconds ƒ/2.8 ISO 1600 15.1 mm (35mm equivalent to 28mm) G1X

What light is that? Looks super bright.

The HD2010, running on a Powerizer LiNiMnCo 26650 18A capable cell.