Talk:Lux

message: I think there needs to be a disambiguation page for lux in terms of light and also the lux gene/operon in bioluminescent bacteria.  —Preceding unsigned comment added by 99.225.24.69 (talk) 16:20, 12 February 2008 (UTC)
replies: text: There is a disambiguation page for lux. It is at Lux (disambiguation).--Srleffler (talk) 16:38, 12 February 2008 (UTC)
thread_title:  Disambiguation Page 

message: From the SI article:
*Symbols are written in singular, e.g. 25 kg (not "25 kgs").
Similarly it is lumen not lumens
213.51.209.230 11:09, 9 Oct 2004 (UTC)
replies: text: OK, point taken 213.51.209.230 16:34, 9 Oct 2004 (UTC)
replies: text: Bobblewik  (talk), whom I invited to comment (see below), is very knowledgeable on SI. Oh, by the way, welcome to Wikipedia, Sonett72. Dpbsmith (talk) 21:51, 9 Oct 2004 (UTC)

text: Plural unit names are used when they are required by the rules of English grammar. They are normally formed regularly, for example, "henries" is the plural of henry. According to Ref. [8], the following plurals are irregular: Singular - lux, hertz, siemens; Plural - lux, hertz, siemens. (See also Sec. 9.7.)
Dpbsmith (talk) 14:32, 9 Oct 2004 (UTC)

text: 1.00 × 103 lx ?
I would write klx, in preference to "1.00 × 103 lx". --Srleffler 05:19, 13 January 2006 (UTC)

text: I think these SI prefixed forms should be removed from the table. Although they are technically correct, the purpose of this table is not to educate the reader about SI prefixes, but to give an idea of different common illumination levels. Moreover, especially 'hlx' is hardly ever used in real life. If I do a google search on 'hlx illuminance', I see 5 technical pages where hlx is used as a unit, the rest being Wikipedia (copies) and lamps that have 'HLX' in their part number. Wikipedia should represent common usage, an not falsely give the impression that "hlx" is a common term. Han-Kwang (t) 08:29, 12 September 2008 (UTC)

text: I'm fine with that.--Srleffler (talk) 04:31, 13 September 2008 (UTC)
thread_title:  Units and symbols 

message: The official SI website says "Unit symbols are unaltered in the plural" (http://www1.bipm.org/en/si/si_brochure/chapter5/5-2.html). This applies to the symbols, not to the unit names. So unit names can follow the local language and spelling when used in full. English language forms are:
*50 metres and 50 m, but not 50 ms
*50 kilograms and 50 kg, but not 50 kgs
*50 seconds and 50 s, but not 50 s's
*50 volts and 50 V, but not 50 V's
*50 lumens and 50 lm but not 50 lms
Bobblewik  (talk) 14:58, 9 Oct 2004 (UTC)
thread_title:  Plurals 

message: According to the official SI website, SI prefix names and the prefix symbols can be added to any SI unit (http://www1.bipm.org/en/si/prefixes.html). Therefore klx and μlx are indeed valid and unambiguous forms. Some prefixes and unit combinations are less common, but SI does not address the issue of familiarity. That is a matter between authors and their readers.
Computing has made more people familiar with small (micro, nano) and large prefixes (mega, giga). I think it is interesting that potentially useful unit multiples Mg and Mm are not more common.
Bobblewik  (talk) 15:16, 9 Oct 2004 (UTC)
thread_title:  Prefixes 

message: :I think these SI prefixed forms should be removed from the table. Although they are technically correct, the purpose of this table is not to educate the reader about SI prefixes, but to give an idea of different common illumination levels. Moreover, especially 'hlx' is hardly ever used in real life. If I do a google search on 'hlx illuminance', I see 5 technical pages where hlx is used as a unit, the rest being Wikipedia (copies) and lamps that have 'HLX' in their part number. Wikipedia should represent common usage, an not falsely give the impression that "hlx" is a common term. Han-Kwang (t) 08:29, 12 September 2008 (UTC)
replies: text: I'm fine with that.--Srleffler (talk) 04:31, 13 September 2008 (UTC)
thread_title: Prefixes revisited

message: I came to Wikipedia to look at the entry to lux because I was wanting some idea of how a 0.01 lux camera would
compare in low light to a 0.1 or 1 lux camera. Like a comparison of what the human eye would see, versus what
a camera at 0.01 lux would see. This may be one of those area too specific for Wikipedia to really cover, but
it would be nice if the lux definition had some more real-world data than scientific data. --Jmccorm 04:18, 13 January 2006 (UTC)
replies: text: You're not really looking for information on lux, you are looking for information on camera technologies and human vision. Maybe you'll find what you are looking for at visual perception, visual system or camera, or one of the related articles. I presume that a "0.01 lux camera" is a camera that the manufacturer claims will take a viewable picture at that level of light. This sounds like something that might be pretty poorly defined—more a matter of marketing hype than detailed specification. You might want to check the manufacturer's website and see if they provide an explanation of what it means. --Srleffler 05:19, 13 January 2006 (UTC)
thread_title:  Less dictionary/science, more real-world? 

message: the article says 1 lux = 1  lumen per square meter.
shouldn't the square meter be cube meter??
and, how many lumens is a average 60 Watts light bulb?
Xah Lee 07:21, 2004 Oct 12 (UTC)
:1. No.
:2. About 870: 14.5 lm/W (according to our light bulb article) × 60 W.
--Heron 08:25, 12 Oct 2004 (UTC)
replies: text: Just to avoid confusion for someone reading this who is not familiar with these units: note that the 14.5 lm/W ratio is particular to incandescent light bulbs, and even then isn't all that accurate and only applies for bulbs around 60 W. Other types of light source have different ratings, and in fact the exact ratio varies from one type of light bulb to another. The article on incandescent bulbs has a nice table comparing the luminous flux of various light sources.--Srleffler 05:19, 13 January 2006 (UTC)
thread_title:  60 watts bulb example & a square meter? 

message: I think the remark below is wrong, for the following reasons:
*Human perception of light intensity is not logarithmic, but follows a power law. That is, equal ratios of light intensity correspond to equal ratios, not equal increments of sensation. See Stevens' power law.
*Although ratios of illuminance can be expressed in decibels, in fact I don't believe they ever are. That is, the comment verges on original research.
*Something's wrong here, anyway, as lux is a unit of illuminance. I don't remember offhand what the unit of light-intensity-reaching-the-retina is, apostilbs or some damn thing like that? but in any case lux is not the right quantity. If this remark belongs anywhere it would be in the article about some other photometric unit, not the lux.
Radiometric measurements involving actual power, i.e. measurements derived from watts, might well use decibels (e.g. to express signal-to-noise ratios).
If I'm wrong about this, apologies. But I'd like to see a source. Dpbsmith (talk) 16:06, 11 May 2006 (UTC)
replies: text: Wrong.  You need to read the famous paper by S. S. Stevens, "To Honor Fechner and Repeal His Law".  He updated the Weber-Fechner law (logarithmic psychophysics) with the more accurate Stevens' power law.  It's OK to cite decibels, but they should not be regarded as perceptually equal units. Dicklyon 07:26, 16 May 2006 (UTC)
thread_title:  Human perception? 

message: Human perception of light, like that of sound, is logarithmic
, so an increase by a factor of 10 in lux can be expressed as an increase of 10 dB in illuminance. With this notation, an increase from 50 klx to 100 klx is an increase in illuminance of about 3 dB.
:Wrong.  You need to read the famous paper by S. S. Stevens, "To Honor Fechner and Repeal His Law".  He updated the Weber-Fechner law (logarithmic psychophysics) with the more accurate Stevens' power law.  It's OK to cite decibels, but they should not be regarded as perceptually equal units. Dicklyon 07:26, 16 May 2006 (UTC)
thread_title: Human perception

message: The use of dB to compare optical powers is always risky, since the dB definition, 10log(power_ratio), conflicts with the definition used in video and image sensors, 20log(voltage_ratio) where the voltage is proportional to the optical power.  So when you see dB, you often can't be sure which it is.  No such problem arises in audio and most other uses of dB, where power is proportional to the square of voltge. Dicklyon 05:47, 21 May 2006 (UTC)
thread_title: decibels in optics and photometry

message: Appreciation to the writer above for citing an important issue.
Care should be taken in the application and interpretation of dB units when used with electro-optic equipment parameters. Care is warranted in such cases because electro-optic equipment often incorporates power-to-voltage converter circuits (photodetector circuits in particular), power-to-current converter circuits (photodetector circuits in particular), and their analogs: voltage-to-power converter circuits (photoemitter circuits in particular) and current-to-power converter circuits (photoemitter circuits in particular).
The definition of decibels (dB) is consistent and unambiguous (including in such electro-optic equipment): 10*log(P1/P2), 20*log(V1/V2), and 20*log(I1/I2) at a given point (at a lens surface, or at a circuit node).
Given a dB value for a given point, one can calculate any or all of the following unambiguously in conventional electro-optic equipment: P1/P2, V1/V2 and/or I1/I2. Given any of the following: P1/P2, V1/V2 and/or I1/I2, one can unambiguously calculate the dB value at the given point.
Care should be taken by writers and readers in assuring that references in dB units are associated with the proper side of any photodetector or photoemitter interface. Persons working regularly with image sensor design or image sensor integration, i.e. persons working regularly on both sides of the photodetector interface, may wish to specify something like "dB optical-side" or "dB electrical-side" in conversation or written narrative; or refer to a specific point ("dB at the objective lens"). This should help to prevent the above-referenced problematic variety of error associated with the use of dB units in electro-optical equipment.
In image sensors, for example, a 10dB loss on the optical side (10:1 power loss through an obscured window, for example) adheres to the definition above at the window, and this hypothetical window-obscurant loss will likely manifest as the same dB-loss (due to window obscurant) value throughout the rest of the (conventional) optics train. But the (photoconductive-mode, for example) image-sensor photodetector converts optical power to electrical current, such that the 10:1 optical power change described above elicits a 10:1 change in current at the photodetector output, i.e. a 100:1 change in power on the electrical side. The loss on the electrical side due to the window obscurant is therefore 20*log(I1/I2) = 10*log(P1/P2) = 20dB. The definition of decibels (dB) is consistent and unambiguous at any given point in the image sensor described above; care should be taken to apply the 2:1 change in dB values that occurs across many conventional photodetector and photoemitter interfaces.
The writer above notes that "no such (issue) arises in audio and most other uses of dB". In support of this characterization, it may be said that as a percentage of citations of equipment dB values, E/O converters and RF modules with square-law responses may host the bulk of such (nonlinear interface) issues with the proper application and interpretation of dB units.
Jplesa (talk) 06:17, 27 April 2010 (UTC)
thread_title:  A clarification

message: I changed the definition to make it clear the Lux is NOT a measure of perceived intensity, but rather a physical measure.  To make the definition definite and complete, we should really include a table and/or plot of the Vlambda curve of luminous efficiency, which I expect is in the public domain, or at least widely copied from the IEC standard. Dicklyon 07:50, 16 May 2006 (UTC)
thread_title: Definition

message: This seems wrong to me. I'd like to see a citation. In Czeisler's work, 10,000 lux is used to reset the clock. 1,000 lux is typical of ordinary workplace illumination and it is not sufficient to synchronize shiftworkers to their schedules, as witness Bhopal, the Exxon Valdez, and numerous other accidents that happened in the wee hours... Dpbsmith (talk) 12:46, 16 May 2006 (UTC)
replies: text: I just removed the biological clock material from the table. An anon editor correctly noted that the cited article claims small adjustments of the biological clock at illuminances as low as 180 lux. That's fine, but it renders this issue not interesting or important enough to include in the table. Rather than a sharp threshold for resetting the clock, the reference shows a gradual increase in clock-resetting from very low levels of light to very high levels. One would presume that this variation is continuous, so there is no particular value that is distinct enough to be worth listing here. The clock-resetting level was only really interesting when it was higher than normal room light anyway. Light makes you feel more alert. Film at 11. (yawn).--Srleffler 23:58, 19 September 2006 (UTC)
thread_title: Biological clock

message: I don't believe the section "Relationship between illuminance and power" belongs here at all. It should go in the article on lumen. Or, it should go in an article about luminous efficacy or the luminosity function and all of the articles on matching photometric/radiometric pairs should link to it.
The current text:
:Illuminance is not a direct measure of the energy of light, but rather of the illumination it provides as perceived by the human eye. Thus, the conversion factor varies with the wavelength composition or color temperature of light. At a monochromatic light frequency of 540 THz (approx. 555 nm wavelength; the middle of the visible spectrum) the power needed to make one lux is minimum, at 1.464 mW/m²; that is, the peak of the luminosity function is 683 lumens per watt, falling to zero in the infrared and ultraviolet wavelengths. Typical light sources have a luminous efficacy much less than this theoretical maximum (luminous efficiency much less than 1). For example, a typical incandescent light bulb has a luminous efficiency of only about 2%.
mixes up illuminance, energy, and power. All of the very confusing photometric (and radiometric) units have different dimensions and different factors that affect them. We really shouldn't be trying to compare thingies that differ by more than one doohickey at a time. 
This section is really about the relationship between photometric and radiometric units. It applies to power (watts) versus luminous flux (lumens). It applies to other corresponding pairs of photometric and radiometric units.
It doesn't apply to energy versus illuminance. 
Illuminance is not a direct measure of the energy of light, for many reasons other than the luminosity function. For example, a strobe light may put out the same amount of energy in 1/1000th of a second that a floodlight puts out in ten seconds... but for that thousandth of a second its illuminance will be ten thousand times higher. Similarly, a bare bulb and a bulb with a parabolic reflector around it may put out the same amount of luminous flux, but the parabolic reflector results in a much higher illuminance over a much smaller area. Dpbsmith (talk) 19:02, 17 May 2006 (UTC)
replies: text: I agree; make sure there's a good explanation in the appropriate article, and replace this section by a brief statement about photometry being different from radiometry, and a link. Dicklyon 21:43, 17 May 2006 (UTC)

text: I agree that section isn't very good, but I think it should be replaced rather than removed. Because of the confusion between photometric and radiometric quantities, every article on photometric quantities and units should contain a paragraph explaining the difference between the two (either a general paragraph, or one comparing that specific quantity/unit and the corresponding radiometric quantity/unit). The articles on luminous efficacy and the luminosity function are (and should be) more technical articles for readers interested in a greater level of detail. The articles on the quantities and units should give a naive reader a reasonably clear qualitative picture of the difference between the photometric and radiometric quantities, without recourse to the more technical articles. --Srleffler 22:10, 17 May 2006 (UTC)
replies: text: I agree. I'm not sure I exactly know how to do it... Dpbsmith (talk) 22:24, 17 May 2006 (UTC)
replies: text: I'm not too pleased with the new long-winded version.  The long discussion of the relationship between lumens and watts might be OK in the lumen article, but not here.  Then we could reference that with a short paragraph.  Also, I believe you've inverted the meaning of luminous efficacy and luminous efficiency, if the article on those is correct. Dicklyon 05:57, 18 May 2006 (UTC)
thread_title:  Picking Nits... just call me an apostilb, I mean apostate... 

message: I admit I was confused and some of my edits may need to be corrected.  There's a difference between the standard frequency at which the 683 lumen/watt is defined (540 THz), and the peak of the luminosity function as adopted by the CIE, which is 683.002 lumen/watt at 555 nm. Dicklyon 21:08, 18 May 2006 (UTC)
thread_title: Another nit:  540 THz versus 555 nm

message: IS there a source to that table? How can starlight be less light than the overcast sky without a moon (assuming you are far from a city)? Where does that extra light come from? -- Cuardin (talk) 06:49, 10 September 2008 (UTC)
replies: text: I agree the table appears inconsistant and lacks sources. I found a reference and modified the table accordingly. Han-Kwang (t) 08:30, 10 September 2008 (UTC)
thread_title:  Starlight versus overcast moonless sky

message: The current definition doesn't make sense to me: 1 lx = 1 lm/m2 = 1 cd·m2·m–4.
Isn't this the same as saying: 1 lm·m–2 = 1 cd·m2·m–4, and therefore 
1 lm·m–2 = 1 cd·m–2, leading to  1 lm  = 1 cd , which is wrong.
But since the definition has survived for so long in this article, I suspect that I misinterpret it. How can something that looks so simple also look so wrong, and still remain uncorrected? In a similar fashion, the definition for Lumen (unit) is fishy. --HelgeStenstrom 08:43, 24 April 2007 (UTC)
replies: text: This stuff always confuses me, too.  I think the issue is that in the definition of lumen, there's a steradian that got dropped becuase it's 'non-dimensional'.  Something like that applies to the lux, too.  I usually end up back in books or tutorials that try to explain it better.  I see what I can figure out the help resolve this... Dicklyon 14:48, 24 April 2007 (UTC)
replies: text: I feel confused too. I quite suggest that the definition should be changed to: 1 lx = 1 lm/m2 = 1 cd·sr/m2. Yufeng.Zhang 13:51, 8 August 2007 (UTC)

text: This just illustrates the pitfalls of trying to do "math" on units. The results don't always mean what you think they do. You have to think about the physics, not just the math. In your derivation, you dropped a factor of 1 steradian, since 1 sr = m2·m-2 = 1. You can drop the steradian for purposes of dimensional analysis, but you have to keep it if you want to deal with units rather than dimensions. 1 lm ≠ 1 cd, even though they have the same dimensions, because these are units of different physical quantities. You can't equate units of distinct physical quantities, even if they happen to have the same dimensions. The correct interpretation of the correspondence between 1 lm and 1 cd derived above is the one stated in the article: "If a light source emits one candela of luminous intensity into a solid angle of one steradian, the total luminous flux emitted into that solid angle is one lumen." --Srleffler 00:15, 10 August 2007 (UTC)
thread_title:  Definition: bad math? 

message: "Candelas are equal to the square of the distance multiplied by the number of footcandles. For example, if your meter is ten feet away from the light source and your meter reading is 10 footcandles, the equivalent candelas equals 10 feet squared (e.g. 100) times 10 -- which equals 1,000 candelas.
The conversion of footcandles and lux to candelas is most accurately achieved in the context of a single point source of light measured in the dark. If the light source is diffused, you should take several readings at different angles in order to calculate an "average" candela measurement."
-69.87.200.181 16:22, 24 May 2007 (UTC)
thread_title:  convert footcandles and lux to candelas 

message: When was Lux unit used from? --maxrspct ping me  15:36, 5 November 2007 (UTC)
thread_title: When invented?/history

message: If needed, I can provide an image of LUX being measured in the Logitech Solar App. As seen here. 71.90.29.110 (talk) 17:32, 8 March 2011 (UTC)
thread_title:  Lux measurement in Logitech's Solar Keyboard 

message: The table of examples primarily cites http://stjarnhimlen.se/comp/radfaq.html#10, a table of things like "how bright is the sun". This is all good, since those are all actual light sources. But the table in our article lists things like "Family living room", which is confusing, since my living room as a whole does not glow. The brightness of a room is probably best measured in luminance, and therefore cd/m2, not Lux.
Not only should the table be fixed, text indicating this distinction should be inserted to avoid confusing the issue for readers (or editors!) in the future.  — Preceding unsigned comment added by Mattdm (talk • contribs) 17:40, 24 March 2011 (UTC)
replies: text: You have it almost completely backward. Illuminance (lux) is the appropriate measure for how brightly a room is illuminated by its light sources. If you want to think about how bright a distant object appears, you want luminance (cd/m2), not illuminance. You use illuminance if, instead, you want to know how well that distant bright object illuminates the Earth. So, if you want an answer to "How bright is the Sun?" you use cd/m2. If you want to compare how well you can see in a room lit by sunlight vs one lit by a lightbulb, you use lux.--Srleffler (talk) 03:58, 25 March 2011 (UTC)
replies: text: Well, I'm not so sure he has it backwards. Lux is a measure of how much light falls on a surface in the living room, and of course it varies from place to place in the room. Nits (candela per square metre) is what a surface looks like when you look at it – its brightness. (It doesn't have to be a distant object.) The number of nits that you see looking at a certain spot on the wall doesn't depend only on the number of lux falling there – it also depends on the paint, the glossiness, the angle you look from, and the angles from which light is falling on that spot. In other words, the nits are what you see. The lux is not. Eric Kvaalen (talk) 17:08, 27 December 2013 (UTC)
replies: text: Ironically, your last sentence is exactly the point you have been arguing against, below. I pretty much agree with you here: lux is a measure of illuminance—that is, how well a source illuminates surfaces. Nits are a measure of luminance, which is how bright a source (or an illuminated surface) looks to an observer.--Srleffler (talk) 07:08, 30 December 2013 (UTC)

text: Yes, I realized that I was arguing a point here that may seem to be contrary to what I have been arguing lower down. But here I'm talking about when you look at a surface. Lower down I'm talking about looking at a source of light, where what matters (most) is the total amount of light it gives you (per square metre of course), not the amount per unit of solid angle. Eric Kvaalen (talk) 12:56, 8 January 2014 (UTC)
thread_title:  Horrible confusion from the table of examples 

message: Hi! I'm thinking about adding a new section about how to estimate (for household purposes, back-of-the-envelope way, ignoring trigonometry) the correct illumination of work and living places. For example, if I want around 200 lux for a bathroom of 10m2, and I'm going to light it with a single light bulb on the ceiling, how powerful must it be? (around 2000 lumen, which suggest using more than one light source). For this I was going to (very briefly) explain such as this: 
# The recommendations for adequate lighting in a given space are given in lux (for example, 500lux for an office). This is a measure of how much light (illumination) there is on a given surface. 
# Light sources such as lightbulbs report their power either as watts or lumens. When lumens are not indicated, you can estimate 1W ~ 15 lm (for incandescent bulbs) or 1W ~ 60 lm for compact fluorescent lamps, and 1W ~ 80lm for LED lamps. Keep in mind those are just approximations, and lights should clearly mark their light output in lumens. 
# Lumen, which lightbulbs are measured in, is candela (luminous intensity) per steradian, a measure of solid angle. So, in layman terms, it measures how much light the bulb emits over a certain portion of space. 
# The steradian has a useful quality: at a distance "A" from the center, the surface it covers is A2. Thus when you are at a certain distance (say, 2m) from a light source, the given light (measured in lumens) is spread over (2m)2, that is, 4m2. 
# Thus, to estimate the lux on your work surface, you can add, for each light source in the room, Lumens/Distance ^2. Example: Your work table is below a 1200lm light in the ceiling, 2m above your head. There is another light of the same power in the ceiling, 2m to your left (thus, \sqrt{8} m from you). The first light is giving you 1200/(2m)^2, 300 lux and second one gives 1200/\sqrt{8}^2, 150lux, for a total of 450lux. 
Keep in mind that all of these are simple, back-of-the-envelope estimations for household use, and that for proper calculations on workplace settings you should contact a professional.
I think this article is the proper place to put this info in (I arrived here through lumen, and made the math myself after I failed to find other sources). If you disagree, could you please suggest an appropriate article? Scarbrow (talk) 07:31, 19 May 2014 (UTC)
replies: text: That might not be appropriate material for Wikipedia at all. By policy, Wikipedia is not a how-to guide. A worked example of how illumination is calculated is fine, but the article already has that. Providing step by step advice on how to determine lighting for a work area is out of our scope.--Srleffler (talk) 16:55, 19 May 2014 (UTC)
replies: text: I agree with you. --Matthiaspaul (talk) 21:46, 19 May 2014 (UTC)
replies: text:  Thank you for your comments, I won't add to the article then. Anyway, at least I got that written down. Some how-tos I found on talk pages on the past were most useful Scarbrow (talk) 11:10, 20 May 2014 (UTC)
thread_title:  Calculating lux on a work surface  

message: While I can appreciate what the user Yonoodle tried to achieve, I have to suggest that these images be completely redone. In their current form they are confusing, and ugly to look at. 
Also, I agree with the technical problems highlighted by user Edgar Bonet above.
FMalan (talk) 15:06, 30 November 2015 (UTC)
thread_title:  Suggest new images need (major) rework 

message: Either “per square meter” or “per meter squared” is fine, but use consistently. — Edgar.bonet (talk) 10:01, 7 December 2015 (UTC)
thread_title: Note

message: I glanced at these in one of the articles tonight, saw the misspelled word "lumimous", and deleted them from all the articles since I thought they hadn't been edited. I put them back after I realized these were updated versions. The misspelled word needs to be fixed: it is luminous not lumimous. I don't have time to proofread these tonight; there are probably other issues.--Srleffler (talk) 06:01, 2 February 2016 (UTC)
replies: text: The misspelling "Lumimous" still isn't fixed...removing. I don't see other major problems; if this spelling error were fixed in images 1 and 4 I would not object to the images being reinstated.--Srleffler (talk) 04:28, 26 April 2016 (UTC)
thread_title: Still need some work

message: Dear Srleffler and all , Sorry for noticing the issue so late after 2 years , i've corrected the lumi"m"ous spelling in the images,
and uploaded the pptx source file to google drive https://drive.google.com/open?id=1M0pXnHxnhkG_vgb8wHB--4qPwt3k5XSD
it is welcome to everyone to correct the spelling issue or some phrases correction and re-upload from other wikimedia url.
still i'm willing to do the job, if there's any suggestions , please also give me a short message at Facebook https://www.facebook.com/profile.php?id=100000740641519  which i will check every day.
Yonoodle (talk) 07:26, 12 December 2017 (UTC)
thread_title: Spelling corrected and source file uploaded

message: Hi, the values listed in the table of lux values for different weather conditions don't really agree with my knowledge from the daylight simulation courses I have taken at my university. Most of the values I know nothing about, but something we often use is the overcast sky since this is used for daylight factor calculations. Here the standard value is 10,000 lux not 1,000 as suggested in the table here! As part of those courses I have also done some measurements to back up calculations, and from those I can confirm that 10.000 lux is pretty much what you get with a normal overcast sky (here in Denmark at least). Obviously the value can be lower if it's a really thick sky cover or something, but I think it should be noted that the 1,000 is a lower bound then. I also find it a bit confusing that there is a "full daylight (no direct sun)" category too. Should that be interpreted as clear sky conditions but only the ambient light (if so I think the value would be lower than with a thin sky cover?), or is that essentially an overcast sky?
For more info see https://en.wikipedia.org/wiki/Daylight_factor 
Here overcast sky conditions are listed with a value of 11921 lux.  — Preceding unsigned comment added by 94.189.3.178 (talk) 19:57, 24 January 2019 (UTC)
thread_title:  Illuminance example values 

message: For both illuminance and luminous emittance, the SI unit is lm/m2.  But to my knowledge, lx=lm/m2 is used for illuminance only. See e.g.  and  — Preceding unsigned comment added by Wassermaus (talk • contribs) 15:26, 17 November 2019 (UTC)
replies: text: Yes, after your edit today I did some quick searching myself and found other sources that suggested the same thing. I removed the section on luminous emittance altogether, since it is no longer relevant to the topic of the article.--Srleffler (talk) 22:01, 30 November 2019 (UTC)
thread_title:  Unit for luminous emittance? 

message: the magnitude-0 star gives 2.08 microlux while magnitude-6 give 8 nanolux, according to the page. probably should be the other way around. i won't switch them around myself because i don't know whether the resulting values would be correct either
Gridzbispudvetch (talk)  —Preceding undated comment added 04:01, 29 November 2019 (UTC)
replies: text: See Apparent magnitude. Larger magnitude means a dimmer star.--Srleffler (talk) 05:32, 29 November 2019 (UTC)
thread_title:  starlight lux rating errors? 

message: This article is awesome. Congrats to the editors! Now I finally understand what light bulb I need for my office.
Don Ema Valecirro (talk) 07:08, 26 April 2020 (UTC)
thread_title:  Kudos to the editors 

message: The article should contain a few worked examples of the relationship between lux and nit in a few common situations, such as maybe a glowing sphere, surround lighting, the sun, a piece of paper, and so on. We got light source A, this emits so-and-so-much light, of which this much reaches object B which in turn itself becomes a light source of such-and-such brightness. I think it would help a great deal for conceptual understanding.  — Preceding unsigned comment added by 77.61.180.106 (talk) 13:00, 1 October 2021 (UTC)
replies: text: That should probably be in Luminance or Illuminance rather than here. The Luminance article has a section on the relationship between the two already.--Srleffler (talk) 02:04, 4 October 2021 (UTC)
thread_title:  Relationship of lux and nit