# Questions tagged [luminous-flux]

Anything related to the *luminous flux* emitted by a light source. The luminous flux is a physical quantity used in photometry to measure the amount of light power radiated from a light source that can be perceived by the human eye. Its unit of measurement in the SI is the *lumen* (lm).

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### RGB LED Selection and Perceived Brightness

I'm trying to design a smart light with 800-1000 lm white LED strings (warm+cool) and RGB, but I'm having a hard time comparing the luminous intensity or sometimes mcd ratings. How can I select red, ...
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### LED : Minimum luminance by lighting

If 7-segment displays on a portable device to be easily legible from say, 10 feet, laid on a surface facing up at a light source (indoor or daylight), what are the minimum luminous intensities I ...
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### What is the mathematical relationship between the resistance of an LDR and light intensity in lux?

I have been surfing the internet and my physics books for the relationship between the resistance of an LDR and light intensity (a formula), and so far I have found nothing. If any of you have a ...
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### Finding the PPF and PPFD using a LED data sheet

I would like to design my own grow lights to grow indoor plants like strawberries, herbs, etc. But I have a problem that I need some help to work out: How many LEDs do I need to light up an area of 0....
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### Continued illumination of LED after removing voltage

I am designing high-speed flash for my microscopy project and as I know from my practical experience when you stop applying voltage on the LED it needs some time to fully stop illuminating, because of ...
1 vote
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### Would connecting multiple light socket splitters together decrease lumens

Sorry if this is a noob question. I'm trying to build a very bright light by combining multiple light bulbs together with socket splitters. My thinking is simply to take three 7 in 1 light socket ...
60 views

### Consistency Concerns Between Series RGB LEDs in a String

My concern/question: If one has a string of series RGB LEDs (w/ independent elements) and was to light green to 100% and red to approximately 75% -- in an effort to illuminate the Amber color -- how ...
154 views

### How to specify UV high brightness LEDs?

I'm trying to find high brightness UV LEDs appropriate for this project: https://www.instructables.com/id/UV-LED-Exposure-Box/ which includes: "The most critical parts of this project are the UV ...
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### How to implement an equation in assembly language using PIC18F and display its result on LCD?

I had a project that requires to measure illuminance(lux) using LDR and display the result on LCD. Thanks to some references from Google, I had managed to build a equation that shows relation between ...
314 views

How do I calculate the Luminous Intensity (cd) of multiple LEDs spread across a 1.5m2 internally illuminated sign element? I have done this by treating it as a point source and adding each led ...
154 views

### Would I get a better lumen output and improved thermal characteristics for the same wattage if I get a higher rated LED? [closed]

I'm planning on building a bright DIY high CRI LED video/photo floodlight out of the following components and considerations: High-power Neutral White (4000K?) LED rated at 95 CRI No add-on lens so I ...
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### Designing brake light with specific luminous intensity

I am currently designing a brake light for a Formula Student car and I am looking into existing solutions on the market for inspiration. The two specific solutions are this, and this. The LED I found ...
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### What is the theoretical limit of lumen/watt for lighting systems?

Nowadays we see LEDs with 300 lumen per watt luminous efficacy. They still waste a lot of power as heat. Now what is the limit of electricity to light conversion? Say we build an LED with 100% ...
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### How can I decrease the brightness of these BA-15 LED bulbs

I'm looking at these LED replacement bulbs for the interior of my sweet conversion van. I'm looking for a more efficient alternative to the BA15 bulbs that are in there already. These bulbs appear to ...
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### High power LED vs. standard LED

How do high power LEDs with forward current of 350mA compare to bright 5mm LEDs with forward current of 20mA? If forward voltage is the same (same color) does that mean light output of 17.5 of 5mm ...
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### Human perceived (relative) brightness of indicator LEDs

Humans looking at colored lights each at the same luminescence perceive yellow as the "brightest" color. Green is somewhat dimmer, and red is very much dimmer. Using a common formula for calculating ...
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### Difference between incandescent/fluorescent/LED wattages?

If the numbers on the 'light output' table at the bottom of this page (here) is correct, and if I have a lamp (like this) that has a maximum wattage of 60 and takes incandescent bulbs: Does that mean ...
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### Solid-state lighting [closed]

Background Consider the following technologies: 100 lm/W OLED (2008, source) 303 lm/W LED (2014, source) 94 lm/W LEP (2015, source) For growing food, the preferred measurement is Photosynthetically ...
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### Why so different lumen efficiencies between mains and 22V halogen?

I was looking for data about halogen reflectors I just bought. They are 50W, 230V. On the package I read 320 lumen and that looked ridiculous to me, then I found this document by GE: Halogen Lamps ...
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