Lighting terminology

[@dianliu2109]

Just in 5 mins, can you imagine? Insanely good explaination, love you sir

[@mikeytobago]

after combing the internet for explanations, i came across this video, and this has to be the BEST there is online! thank you so very much! am a school teacher and i would play this for my class.

[@randall1fc616]

Sir, you'd translated something so complex and difficult to understand into something simple and concise. I was able to submit my report after watching your lesson. Thanks a lot!

[@danielpereiraballesteros9561]

1:16 1:16

[@danielpereiraballesteros9561]

F 1:34 1:34

[@lucafogliati6050]

What a masterclass.Everything made simple.Thank you!

[@rodericksibelius8472]

SIMPLE AND DIRECT UNDERSTANDING, GREAT TEACHER.

[@smithcodes1243]

What a concise and simple explanation!

[@twinkledoucheful]

I do not know how i got here at 2 in the morning but thanks for the useful knowledge, something new for me !

[@SignifyCompany]

Hi Faisal, we're glad to hear you like the video :)

[@ravishanker2663]

Most useful animated video with excellent explanation 👍 Thank you very much sir 🙏

[@rogiervdheide]

Dear Mark, thanks for this lesson on the fundamentals. But, I think it is confusing. See the summary at 5:40. You write that flux "depends on solid angle". Actually, flux is the amount of lght energy emitted by the source, independent of the angle of emmittance. Flux does not depend on solid angle. Lumens or "flux" simply quantify the total amount of light emitted by a lamp, regardless of the direction of the light. On the other hand, candela or intensity refers to the amount of light emitted by a lighting device in a particular direction. I think that both "flow in air" and "dependence on solid angle" are not the best explanations of luminous flux. I also think that describing luminance as dependent on direction and specularity is confusing for most students. Luminance really is "perceived brightness" and greatly depends on the absorption of light by the surface you are observing in the first place. I agree that this is the most useful unit of the whole lot, though it's perhaps te hardest one to grasp. The Exitance is much less relevant if relevant at all in architectural lighting. Greetings from a friend!

[@naimgorgani953]

Isn't "Lumen" (Luminous Flux) a measure for total light output in all directions? And Candela is supposed to be intensity of light in a specific direction. It feels like these were explained instead of each other. Or am I mistaken?

[@dipankargupta550]

Lumen = luminous flux per unit solid angle. Candela = lumen per area.

[@We_Talk333]

Thanks for the information of the fundamental history on lighting.

[@jmjabonitalla5922]

You’re a great teacher sir.

[@Samurai_420]

This is simply the best video for understanding all the terminology w.r.t light. I had a lot of confusion but it has been cleared. Thanks a lot sir for your video.

[@logeshwaranrk]

If I am not wrong, the unit of Luminance is cd/m^2 🤔🤔🤔

[@Prabhath_the_Dawn]

Thanks so much :) It was very helpful. Cheers...

[@GBCR]

I don't really understand why Flux and Illuminance are separate - it appears they measure the same thing, the intensity/amount of light in/on 1ft²?

[@SignifyCompany]

Hi, thanks for reaching out. In photometry, illuminance is the total luminous flux of light incident per unit area. In other words, luminous flux represents the total amount of light emitted by the source, while illuminance refers to the total amount of light received by an object. You can learn more about luminous flux here: signify.co/3CZriCG And about luminance and illuminance here: signify.co/49edZKT Thank you!

[@nurlatifahmohdnor8939]

(C) 2019 Signify Holding Philips is a lamp. Philippines is a country.

[@robimaren3247]

Can we get description with metric units ? And not with this american units ?

[@nenolima5595]

Nice explanation... do you have more practical examples of this just to familiar with usage... because its so good matter and in begin we get so confused even with so good explanation... Let me synthesise it with my understand: 1 - footcandle:a messure of light light that a source spread in the air. 2 - flux: its the way of light we see from a source light 3- illuminance: its the light that a object receive. 4- luminance: the light spreads from a surface area. If all its right im learning well with u... now my question: How many light... how many lux or lumens (if theres difference) from the spotlights do I need to luminate a table with size 2m length and 0.50cm width? And how the distance shoud they (spotlight) be from the table?

[@SignifyCompany]

Hi there and thanks for reaching out. We do not carry out lighting calculations on request like these, but we do provide guidance in other videos. Please view philips.to/2zUzAYR and philips.to/2zUzCzX. Alternatively you can select products from our online product catalog and download the data (photometrics) from there. Many thanks.

[@gyanguru-pathtoexcellence]

You may check these videos for more detailed explaination Lighting design Terminology Part-1 kzbin.info/www/bejne/h2GUpoOuhcl3r5o Indoor Lighting Design Part -2 ( you can learn how to calculate the number of luminaries and factors that to accounted to calculate the same) kzbin.info/www/bejne/eGrLe3Z3d6uNr5Y

[@gyanguru-pathtoexcellence]

You may check these videos for more detailed explaination Lighting design Terminology Part-1 kzbin.info/www/bejne/h2GUpoOuhcl3r5o Indoor Lighting Design Part -2 ( you can learn how to calculate the number of luminaries and factors that to accounted to calculate the same) kzbin.info/www/bejne/eGrLe3Z3d6uNr5Y

[@samelorc]

Nice explanation! Very informative.Thanks!

[@lindseyjames4502]

samelorc

[@gelmiricardo8229]

excelente explicacion muchas gracias

[@Fotonicastudios]

Candela measure lights in any and all directions??? This is not the luminous flux? or im wrong?? Thanks

[@gaborzsamboky3252]

I think the confusion arises from this: While the candle is visible from every direction, the light source's intensity (candela) measures the brightness of the beam in a particular direction. This measurement is only concerned with a limited area of the imaginary sphere that surrounds the candle. In order to avoid even more confusion introduced by the term steradian, think about it as a limited surface area of a sphere that is bordered by a circle. The total surface area of a sphere is made up of roughly 12.57 steradians. Conversely, one steradian is somewhere between 1/13th and 1/12th of the total surface of the sphere. For a simplified illustration of this phenomenon, the presenter used a frame in this video (1:10). Now, back to the candela. At one point in history humanity agreed that the intensity of the light that a "standard" candle emits in the mentioned direction (one steradian) would be identified as one candela. Which is nice, but we also wanted to determine another practical measure, the total quantity of visible light, flowing from the light source, aka the luminous flux or luminous power. For the utter confusion of future students the measure of luminous power or luminous flux - called lumen - was defined in relation to the luminous intensity, candela. It was said that if the light source's intensity is one candela, then the amount of light flowing in the direction of one steradian would be identified as one lumen. Hence, the total quantity of light emitted by the candle equals 12.57 lumen, the number of steradians in the entire sphere around the candle. (see at 1:19 in the video) On one hand it is pretty obvious that there is a strong correlation between the intensity of a light source and the total amount of light it emits in a certain direction, but on the other hand this circular reference between candela and lumen can easily create confusion. One might look at it as multiple aspects of the very same thing. In layman’s terms both candela and lumen are concerned with the amount of light, but while candela refers to the intensity of the light source, lumens refer to the total amount of light flowing from it. The intensity of a "standard" candle is one candela which generates one lumen of light flow for each steradian, a 12.57 lumens in total.

[@tedreaves4826]

Great teaching,,,,,!!!

[@cloviscareca]

I use a Phillips 250W sodium lamp at my bedroom. I fixed the ballast in the corner and the lamp in the middle of the ceiling. Is using this lamp recommended?

[@SignifyCompany]

Hi Matheus, thanks for getting in touch. It would be great if you could fill in our online contact form and a member of our consumer care team will be able to assist you further: philips.to/2HL0KHS. Thanks!

[@pamelaharden6303]

You explain it so clearly. Thank you, thank you!

[@imooddesign5710]

Nice explanation...

[@khannawaz2600]

Thank you so much Professor

[@evab6420]

Hi, what is lumionous distribution angle? Thank you...

[@SignifyCompany]

Hey Eva, luminous distribution angle describes the spread of light from a lamp or luminaire. Beam angle is the angle at which intensity is 50% of maximum x 2 (each side of the maximum). Hope this helps!

[@chunheitse9741]

very helpful!

[@kritikavashishtha4406]

Perfect!

[@hemakshpatil8962]

Hello Sir need your help for calculating brighness. Please provide contact details.

[@SignifyCompany]

Hi there, thanks for reaching out. Unfortunately, this is not something we can assist you with. We'd suggest the use of a brightness tester. Thank you!

[@manojillangasooriya3590]

Love it

[@Train1587]

Where 12.57 co e from

[@momhn4283]

12.57 is 4*pi. A point source with a luminous intensity of 1 candela emits lights at lumen for each steradian (solid angle). Because a sphere is made of 4*pi steradians, this means that the point source emits a total of 4*pi (=12.57) lumens in all directions.

[@vuhan8277]

@@momhn4283 thanks mate!! that makes sense.

[@cengeb]

let's consider our Card Again....Sweater!

[@thordave6606]

ayooow... check ra kog suga

[@Techvir4790]

😱😱😱😱😱😱😱u r still live 😱😱😱

[@thushar6794]

good

[@MrSauske98]

Very good

[@PANZER7910]

I stop watching immediately when he use foot

[@Zenangsty]

haha yes! get with the metric system already!