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How much watt I need for LED bulb to get the same amount of light produced by 32 Watt CFL bulb? So, comparing lumen is the right way to find out the difference between these two light source?

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Yes, comparing lumens of the two light sources is the right way to compare their perceived brightness. To get an LED that looks about as bright as a 32 watt CFL, find how many lumens are radiated by that CFL, and look for an LED with a similar number.

There is also a quick rule of thumb. LEDs and CFLs are approximately equal in efficiency (the most efficient LEDs or CFLs achieve around 100 lumens per watt), so a 32 watt CFL will require approximately a 32 watt LED to have equal brightness. Of course this is just an approximation, and there's wide variance in the efficiencies of individual CFLs or LEDs, but this will get you in the right ballpark.

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Just lumen comparison is not enough. A CFL will emit X lumens but it does that in all directions. An LED emitting same X lumens may give a higher lux or lumens/sq area depending on its photometry or lensing design. With an LED you get the light where you want it and not in all directions. Although there are now LED lamps that more or less emit in all directions but to my mind that is a waste and the lamp design is not exploiting the LED feature or being able to direct the light where most needed. This is like taking a shower in a shower head that is spherical and emitting water in all direction as opposed to a flat shower head giving you the water where needed... :)

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Watt shows how much power it consumes.

Lumen shows how much light flux is output by a light source.

Lux shows how much light a human eye perceive: \$\text{lumen} = \text{lux} \cdot (\text{area})^2\$.

Efficacy shows lumen per watt.

You can compare two source by lumen in terms of amount of light. If they are both commercial light, lumen value should be already defined on its box or specification on the producer's or seller's webpage. It is not possible to say what LED you need without knowing the LED's lumen/wattage/efficacy and CFL's lumen or efficacy.

You use CRI (color rendering index) in terms of light quality which you may not find it on the specs.

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  • \$\begingroup\$ Just a small correction, Lumens show light flux scaled to the human eye. My 780 nm diode laser outputs zero lumens, (it's below the range of human vision) but 70 mW of light. \$\endgroup\$ Jan 7 '15 at 17:19

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