Talk:Lumen (unit)

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Help with this template Comments: edit – history – watch – refresh There appears to be little in the way of science on this page. Crucial things such as conversions and uses need to be here, as currently there is too much in the way of computer related buzz words. Either the two should be more separate, of the computer term 'Lumen' be defined more obviously.

[edit] Needs clarification or at least referencing

A standard 100 watt incandescent light bulb emits approximately 1700 lumens in North America and around 1300 lumens in 220 V areas of the world. See luminous efficacy for the specific efficiency of various types of electric light sources.

At first glance, it makes absolutely no sense as to why a 100 watt bulb would be 1700 lumens in North America and why a 100 watts elsewhere would be any different. Voltage as the only controlled parameter has absolutely no affect on lumens per watt!

Lumens per watt is affected by filament temperature and envelope transmissiveness, but neither of those are controled by geographic location or voltage.

Thanks! -Jesse —Preceding unsigned comment added by 64.146.180.232 (talk) 18:32, 4 December 2007 (UTC)

The voltage is not the only controlled parameter. The thickness of the filament is another. Light bulbs designed for 220 V are designed differently than those made for 110 V. Be aware also that light bulbs are nonlinear devices. The resistance of the filament varies with voltage.--Srleffler (talk) 00:10, 5 December 2007 (UTC)

I realize that voltage is not the only controlled parameter -- but it's the only one that the article mentions as being the cause of less efficient lumens/watt. I also realize that incandescent light bulbs are non-linear, although it would be slightly more exacting to say that the resistance of the filament is affected by temperature, which is affected by wattage and dissipation, and wattage is affected by resistance and voltage, and so on. The only controlling parameters I can think of which control lumens/watt would be envelope transparency, filament surface temperature, and filament material, and none of those are tied only to voltage or operating in other parts of the world. There is no reason that an equal surface temperature, filament composition, and bulb transparency could not be done on both 110v and 220v lamps.

Is the article saying that 220v filaments are designed to run cooler, thus putting out more of their total energy in non-visible regions? or is it saying that they are running so hot that the same happens?

I'm not saying that the average 220v bulb is or is not the same efficiency as the average 110v bulb -- I do not know -- but I guess I'm saying that the article is dreadfully ambiguous, and it makes a statement that doesn't even make sense, and it doesn't give a cause for the phenomenon, nor does it cite any references. I'd say it is closer to "whimsical banter" and doesn't even rise to the level of "Original Research."

Does anyone mind if I remove that statement in a week or two if nobody finds some references? Thanks & Keep up the good work. -Jesse —Preceding unsigned comment added by 64.146.180.232 (talk) 03:30, 6 December 2007 (UTC)

I rephrased it to remove the impression that we are talking about the same bulb being run on two different voltages. It would be helpful to add a citation to support the two values. Removing the statement would not be appropriate unless you have strong reason to think it is untrue. Note that all of the discussion above is original research, and cannot be used to justify changing the article. Even if we obtained an explanation for why the efficiencies are different, there would be no reason to add that to the article. It's beyond the scope. The bulb outputs are given as a practical example of lumens. They don't need to be explained here. --Srleffler (talk) 06:26, 6 December 2007 (UTC)

I suspect the solution to this puzzle has to do with bulb lifetime. From some searching I did online, it appears that bulb lifetime changes very dramatically with voltage (proportional to the twelfth power).[1] They probably have to sacrifice efficiency to get decent bulb lifetime at the higher voltage.--Srleffler (talk) 06:40, 6 December 2007 (UTC)

Removing (or moving to talk pages) is quite appropriate for material for which there is no reliable source. See [2] (which at the time of my writing) says: "Any material that is challenged or likely to be challenged must be supported by a reliable source. "Original research" is a claim for which no reliable source can be found. Producing a reliable published source that advances the same claim taken in context is the only way to disprove an assertion that a claim constitutes original research. If there is a source, but the source or claim is disputed, that is not original research but rather of a question of reliable sourcing or undue weight. However, using information from references out-of-context or to forward claims not directly supported by the sources is original research."

I don't know who made the claim that 220v bulbs produce less lumens per watt then 110v, but I don't take it to be true. I know that it's certainly not always true (for example, the most efficient incandescent 220v bulb is better then the least efficient 110v. The reverse is also true.) WP Official Policy is that the only way to counter the claim of original research is to provide reliable sources. I don't know who made the claim, and I don't know if they were correct -- maybe they were, maybe they weren't. But they provided no references, so an average reader has no way of knowing. By the way, in my comments here, I am challenging the afore mentioned statement as being "Original Research."

I would propose that the comparison of incandescent bulb efficiencies be replaced with a simple statement like "The ability of lightbulbs to produce visible light is measured in lumens. Some types of lamps, like incandescent, tend to produce more of their output energy in non-visable regions and less in the visible, and so produce less lumens per watt, then, lets say, a flourescent or sodium vapor lamp, which tend produce more visible light per watt." (If lamp efficiency even needs to be discussed here -- since I think lamps have their own section..) Can anyone give me a single reason that removing an unreferenced statement of questionable accuracy would be somehow not appropriate? Having that unreferenced OR statement there is inappropriate, according to WP Policy.. The statement is not always true, and I'm not convinced that it's even "usually true."

By the way, I forgot to ask before, but is this article someone's pet project? If so I understand how you could feel intruded upon by my wishing to effect WP Policy compliance and meaningfulness to this article. If it's someone's pet project, just say so, and I'll go away and not bother you any more! I wouldn't want someone else trying to edit my personal webpages..! Otherwise, there is A) No reason whatsoever that a disputed unreferenced statement should exist on WP, and B) No reason whatsoever that said disputed unreferenced statement shouldn't be removed. Thanks and keep up the good work! -Jesse

PS:The fact that our conversation is original research is besides the point. The point is that the material in question is original research, and according to WP policy should not even exist to begin with (unless with valid references) -- you make it sound as if unreferenced statements can only be removed if they are proved wrong using valid references. But that of course is exactly the opposite of WP Policy which says they may be removed unless proved TRUE with valid references. -Jesse —Preceding unsigned comment added by 64.146.180.232 (talk) 05:31, 7 December 2007 (UTC)

I completely missed this reply (and your subsequent edit to the article). You are quite right that unsourced material can in general be deleted from the article. However, deleting material that is not really in doubt or that can be easily sourced might be seen as disruptive editing. The reason I brought up the fact that the conversation above involves original research was to point out that argument about why a 230 V bulb might be less efficient than a 120 V bulb is completely irrelevant to whether that "fact" should be in a Wikipedia article. Either the claim can be sourced or it can't. Argument about why it might or might not be true is interesting, but irrelevant.--Srleffler (talk) 04:08, 27 May 2008 (UTC)

Just for fun, I looked up some 230 V bulbs. Philips has a 100 W 230 V bulb that puts out 1380 lm. My favorite local industrial supply company, McMaster-Carr, stocks 3 standard "general purpose" 100 W bulbs: a 230 V model that produces 1270 lm, rated for 1000 hours, a 120 V model that produces 1600 lm, rated for 750 hours, and a long-life 120 V model that produces 1470 lm, rated for 1500 hours. A survey of 120 V bulbs' package statistics[3] gives output ranging from 1585 to 1750 for standard bulbs. So, a quick survey seems to support the statement that standard 230 V bulbs are less efficient than standard 120 V models.

Having done some reading and thinking on this since we last talked, I've learned that one can produce bulbs that are much more or much less efficient, at any given voltage. There is a tradeoff, though, between efficiency and bulb life. Standard ("general service") 100 W light bulbs are designed for bulb life in the 750–1000 hour range. Designing a bulb to run for this length of time at 230 V requires a cooler filament temperature, and therefore less efficiency. One can design a bulb to be more efficient but last for a shorter time, but that wouldn't be a "general service" (standard) bulb. Projector bulbs take that approach. Alternatively, one can design a bulb for longer life but at the expense of reduced efficiency, as in the example of the 1500-hour "long-life" bulb above. At any given rated lifespan, though, a 230 V bulb will be less efficient than a 120 V one with the same power rating.--Srleffler (talk) 05:31, 27 May 2008 (UTC)