# Lumens, candelas & equivalent LEDs

• hl_world
In summary: Additionally, the distance at which you hold the LED can also affect the perceived brightness. Therefore, it is difficult to determine the exact millicandela rating of the keychain LED without further testing. In summary, the millicandela rating of an LED can vary depending on various factors such as angle of view, wavelength, and distance. Further testing is needed to accurately determine the millicandela rating of the keychain LED.

#### hl_world

I'm trying to determine the millicandela rating of an LED from a keychain to find equivalent LEDs of different colours. The keychain LED specs are as follows:

Luminous Flux value: 4 lumens (from box)
Viewing Angle: 30° (I got this value by comparing to LEDs with marked angles)
Wavelength: 650nm, maybe shorter (again from comparison)
Diameter: 5mm

Now I used http://led.linear1.org/lumen.wiz to get the millicandela rating but it seems to take a value of ~19000 millicandelas at 30° to get ~4 lumens but it only seems as bright as one of my loose LEDs (10000 mcd, 20°, 630nm). Admittedly, I held it a little further back but when both spot sizes were equal, so was the brightness. Does this seem right?

The answer to your question is that it depends. The millicandela rating of an LED is determined by the amount of light it emits in a particular direction and at a particular wavelength. The millicandela rating can vary depending on the angle of view, wavelength, and size of the LED. It is possible that the LED on your keychain has a higher millicandela rating than the loose LED you are comparing it to. In order to get an accurate comparison, you would need to measure the millicandela rating of both LEDs.

Based on the information provided, it does seem like the keychain LED has a lower millicandela rating than the loose LED with similar specifications. However, it is important to note that the millicandela rating is not the only factor that determines the brightness of an LED. The viewing angle, wavelength, and distance from the light source also play a role in perceived brightness. It is possible that the keychain LED has a wider viewing angle and a different wavelength, which could affect how bright it appears compared to the loose LED. Additionally, the accuracy of the website's calculation may also be a factor. It is always best to test the LEDs in person to get a more accurate comparison.

## 1. What is the difference between lumens and candelas?

Lumens and candelas are two different units of measurement for light. Lumens measure the total amount of visible light emitted by a source, while candelas measure the intensity or brightness of a light source in a specific direction.

## 2. How are lumens and candelas related?

Lumens and candelas are related by the inverse square law. This means that as the distance from a light source increases, the number of lumens per unit area decreases, resulting in a decrease in candelas. In other words, as the distance from a light source increases, the light appears less bright even though the total amount of light emitted (lumens) remains the same.

## 3. What is the difference between lumens and equivalent LEDs?

Lumens and equivalent LEDs are both units used to measure the brightness of a light source. However, lumens measure the total amount of light emitted, while equivalent LEDs indicate the brightness of a traditional incandescent bulb that would produce the same amount of light. For example, a 60-watt incandescent bulb is equivalent to approximately 800 lumens.

## 4. How are lumens and equivalent LEDs calculated?

Lumens are measured using specialized equipment, while equivalent LEDs are calculated based on the wattage of traditional incandescent bulbs. The Federal Trade Commission requires that all light bulb packaging display the lumens and equivalent LED information to help consumers make informed decisions about the brightness and energy efficiency of their lighting options.

## 5. Are lumens and candelas the only factors to consider when choosing LED lights?

No, there are other factors to consider when choosing LED lights, such as color temperature, color rendering index (CRI), and beam angle. Color temperature determines the warmth or coolness of the light, CRI measures how accurately colors appear under the light, and beam angle determines the spread of light. These factors can greatly affect the overall quality and appearance of the light emitted by an LED bulb.