What is Lux: Definition and 29 Discussions

The lux (symbol: lx) is the SI derived unit of illuminance, measuring luminous flux per unit area. It is equal to one lumen per square metre. In photometry, this is used as a measure of the intensity, as perceived by the human eye, of light that hits or passes through a surface. It is analogous to the radiometric unit watt per square metre, but with the power at each wavelength weighted according to the luminosity function, a standardized model of human visual brightness perception. In English, "lux" is used as both the singular and plural form.The word is derived from the Latin word for "light", lux.

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  1. X

    I Lux & Lumens -- how do they work?

    Hello ! I've got a problem understanding what are Lumens and how do I look at lux as well. For example here : It makes 800 Lumens in 1 m^2. Does it mean that in every direction in 1m^2 there are 800 Lumens ? Or when I have a light bult with 800 lumens : Those 800 Lumens in light bult...
  2. flying_bear

    I Lux-meter, candelas or lux, measuring nits in practice

    My lux-meter can be used in two modes, candela and lux. How do I use it to accurately measure a display's luminance in nits? The screen isn't Lambertian, I have to assume this as an unknown. I'm interested in the luminance as seen by the eye looking at the screen perpendicular to it. Now, first...
  3. S

    Calculating distance between lux meter and light source

    I am currently performing some experiments to calculate the distance between a light source and a lux meter where the light source points directly towards the lux meter. Is it possible to calculate the exact distance between the light source and the lux meter given that we have a lux value...
  4. Z

    B Adding up illuminations in lux

    Hello, I just found on google, that 1,5lx + 0,5lx=2lx. I wanted to check if it´ s true, but i couldn´´ t find anything on the internet. So was Google right or not?
  5. S

    B Converting Lux to W/m^2 for Solar Radiation Measurement

    For a physics project, I'm planning to investigate the relationship between the number of slits in a diffraction grating and the intensity of the central maxima. The light meter which I'm planning to use to measure the intensity gives me a result in LUX. I know the wavelength of the red laser...
  6. N

    Convert Lux to RGB: 4 Values to RGB/Hex Color

    I have an optical sensor that outputs 4 values in the following format: [ Red, Green, Blue, IR] where each value is in lux. I want to take this output and render a color on my pc. I'm not sure how to convert this into a regular RGB (0-255)/hexcolor value. Is there a good place to start? The data...
  7. R

    Selective Incident Headlight Intensity Measurement

    Hey guys, I am trying to come up with an idea to measure incident intensity of headlights from an oncoming car for one of my uni projects. This wasn't specifically assigned project topic, we get to choose what we want to do. It's my Instrument and Measurement unit, and I had this idea thought it...
  8. mammou manel

    B How do I convert from lux to candela?

    hello i'm working on a project that consist on reading the light of LEDs on PCB to determine the color code (R,G,B) and light intensity but the sensor gives me values in LUX which is the illuminance and i need to convert them to Candela I found this formula in wikipedia but i didn't understand...
  9. T

    Measure LDR Light with Microcontroller - 10bit Resolution

    I have a micro-controller with 10 bit resolution. How can I convert the voltage or digital output of the microcontroller to a Lux reading ?
  10. Garth

    A Did the LUX Dark Matter Experiment Fail to Detect Dark Matter?

    The negative findings of the Large Underground Xenon (LUX) dark matter experiment, which is a 370 kg liquid xenon time-projection chamber that aims to directly detect galactic dark matter and which were published at the international dark matter conference in Sheffield, UK, raises questions...
  11. K

    A LUX Dark Matter Experiment Ends With No WIMPs Found

    widely reported in all science channels LUX Dark Matter Experiment Ends With No WIMPs Found what are the ramifications to SUSY QG string theory LQG MSSM dark matter etc based on this results? how likely is dark matter WIMP hypothesis in light of this null result, and of neutralinos Does this...
  12. E

    Struggling with light calculations (incident power output)

    Hi guys, not sure if this is the right place. Its to do with an electronic project I've been working on. However please point me somewhere else if you know anywhere better suited! (It is quite a long post sorry) Basically, I have created an LED array used for stimulating cells with light and I...
  13. S

    Relation between lux and W/m^2

    Homework Statement I posted this in anther forum but I think it might be better to post it here. I was wondering if anyone could help me understand the conversion between lux and W/m2 with relation to luminous efficacy (lm/W). Thanks :) Homework EquationsThe Attempt at a Solution
  14. C

    How can I convert lux to watts for CFL bulbs?

    Hello all, I've currently got a swirly CFL bulb that I lit up wirelessly and took some measurements of using a light sensor which returned the data to me in lux. How can I get from lux to watts? As I understand it, lux is a measurement of lumens per unit area, so do I have to somehow find the...
  15. P

    How to Calculate Light Emitted from an LED Screen

    Hi, I have a question how to calculate the light emitted from a LED screen. The LED display is rated at 5000 nits. Total size of the display is 64sqm. (8m x 8m touching the floor) I would like to calculate the total light emitted, the light on the floor in front 1m away and the light on the...
  16. F

    Calculating irradiance from lux of a halogen lamp

    Hi all. We're currently working on a project and need to know the irradiance hitting a steel sheet some distance away from a halogen lamp. The setup looks like: The problem is we can only measure the lux at the surface of the steel sheet, and I believe in order to convert lux to irradiance...
  17. litis

    Measuring Illuminance with Lux Meter - Can I Make Conclusions?

    Hi, I have a question. I have measured with lux meter the illuminance of the room. When in front of the photoelement I put my plastics - colourless, green, red, blue. The lux value had decreased in the same tendency - from the colourless to the smallest value of blue sample. So, can I made...
  18. J

    LUX Results: Trouble for WIMPs Dark Matter Models?

    Does this spell trouble for WIMPS based models of Dark matter ? http://www.nature.com/news/no-sign-of-dark-matter-in-underground-experiment-1.14057
  19. bcrowell

    Exploring the Limits of Dark Matter Detection: Insights from the LUX Experiment

    An article in Nature reports a negative result from the LUX experiment's attempt to directly detect dark matter: http://www.nature.com/news/no-sign-of-dark-matter-in-underground-experiment-1.14057 Can anyone give some context? How does its sensitivity compare with that of previous...
  20. Y

    Converting Lux to Watt for Measuring Light Power

    Hi! I need a little help. Here is my problem, I have a light source and a monocromator that separates the white light to to its components of different wavelenght. I want to measure the power of the output light which has a single wavelenght. I am using a Lux meter to measure the illumation of...
  21. J

    Converting Volt to Lux using a solarimeter

    Homework Statement Hello, I'm trying to use a solarimeter (thermopile) to measure the direct flux of solar radiation, in clear conditions, over varying solar zenith angles. The equipment has an output of volts, but I need to convert this to Lux and then convert this to watts per meter...
  22. C

    Converting radiometric units (W/m^2) to photometric units (Lux)

    1. I am doing a lab about solar radiation. We collected data using a lightmeter which measures illuminance in lux. Now to calculate the optical depth of the atmosphere I either need to find an expression for the solar constant in lux or be able to convert illuminance values in lux to W/m². The...
  23. phy_optics

    Converting Lux to Watts: A Quick Guide

    Hello frnds! Can anybody convert the following factors? V/(lx-s) to V/(um/cm2) at 555nm ?? Thank you.
  24. S

    Calculating Power from Lux of a Solar Cell

    Is there are way to find out power from lux entering a solar cell? I currently have the area of a solar cell 127.2 cm square, and the lux reading 8434 lux I have heard of the equation watts per metre square. However that's not the equation for lux right?
  25. P

    Conversion to lux (Light intensity)

    How would I go about converting 59.7 mw/m^2 to lux? I would appreciate any help I can't find an equality.
  26. J

    Measuring laser output with Lux meter

    Hiya, Question 1: (Main question) I bought a lux meter while understanding very little about how light is measured. I'm hoping to measure the output of a laser in mW. I assume it's possible to do this at least to an accuracy of about 10-20% which is all I need? If so, please could someone help...
  27. T

    What Are the Differences Between Nits, Lumen, Lux, and Candela?

    Hi all, I'm trying to understand the difference between nits, candela, lumen and lux. Just to make sure I've got this right, I'll paste in four concise descriptions for each of the units, and if anyone can alter/adjust them, that would be great. I imagine nothing could be clearer than...
  28. D

    Lux Lumens and Watts per square meter

    Homework Statement I am looking for a conversion factor that will ultimately get me from units of lux (illumination) which is a weighted scale of light intensity, to watts per square meter, which is not weighted. Homework Equations None availiable The Attempt at a Solution I am...
  29. A

    Plotting Resolution Against Lux in Excel

    every subect seem to be different! which kind of graph and a lot what axis do i plot, if i was to do plot resolution against lux! plus anyone kno the proper way to do this in excell. thanks