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# Possible replacement for LPM?

#### Cube777

##### New member
Using a relatively cheap lux meter and THIS table, can't you calculate the approximate power of a laser if you have it's wavelength and lux? It will probably not be as accurate as a LPM but certainly a cheaper solution!

#### Moistenator

##### New member
People already do that. Judge the output by how bright the beam is...

#### DrSid

##### New member
If you had such table for specific luxmeter, we could talk. The meter would have to be able to measure whole output of the laser though. It it only had small sensor, and you put 2W of 445nm into it, I bet most luxmeters would just smoke a bit and die.
It would be simple to compare lasers though. If you had one calibrated/trusted laser with same wavelength as tested laser, you might even compare their brightness indirectly, like shining at wall at night and measuring the reflected light at some distance.

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#### ryansoh3

##### New member
Unfortunately, Lux and Lumens are different measurements.

IIRC, lumens measures the total output and lux measures light for a specific area.

To measure lumens, you would need an integrating sphere which some flashaholics have. They're hard to make and even harder to calibrate.

Looks more or less like this:

However, I do see some methods using an integrating sphere to measure the laser output:

At this point though, getting an LPM would be cheaper and more convenient.

Cheers!

#### Cube777

##### New member
Thanks for all the replies! I seriously need to stop thinking how to replace a LPM!:banghead:

#### lasersbee

##### Well-known member
Using a relatively cheap lux meter and THIS table, can't you calculate the approximate power of a laser if you have it's wavelength and lux? It will probably not be as accurate as a LPM but certainly a cheaper solution!

Been there.... Done that...

Jerry

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