# Easy to Understand Lumens Vs Lux Explanation

#### fixit7

##### Member
So it looks like lux is variable as it varies with the object it is striking. The lux reflected off a mirror would be higher than from reflection off a black cloth.

Whereas lumens is good indicator of how much light a light is giving out.

#### Bullzeyebill

##### Moderator
Staff member
Actually. the light reflected back from a medium would show the perceived brightness of that object. Go up to a black wall and point a light meter at the incoming light and you will get a lux reading no different than shining the light at a white wall, if the distance is the same.

Bill

#### brttina

##### Member
Thanks for the sharing.:twothumbs

#### TEEJ

##### Well-known member
The "target" is a lux meter.

The meter is calibrated to the size of its sensor, so, the lux (Lumens per square meter) is calculated from whatever hits the sensor of known size.

The actual UNITS are expressed in terms of lumens per square meter (Lux).

The throw unit (cd) is expressed in terms of lumens per square meter at one meter distance.... even though the actual throw is basically never that number at that distance... as that number is merely useful for calculating the lux on target at long ranges, where a thrower shines, so to speak.

#### TEEJ

##### Well-known member
How big is the target? Is it 1m^2 or an infinite wall, at 1m distance?

Wondering how to glean hotspot vs corona information.
The "target" is a lux meter.

The meter is calibrated to the size of its sensor, so, the lux (Lumens per square meter) is calculated from whatever hits the sensor of known size.

The actual UNITS are expressed in terms of lumens per square meter (Lux).

The throw unit (cd) is expressed in terms of lumens per square meter at one meter distance.... even though the actual throw is basically never that number at that distance... as that number is merely useful for calculating the lux on target at long ranges, where a thrower shines, so to speak.

As for corona and hot spot, spill, etc.... its information that is typically not available.

If looking for throw, assume there is no corona or spill, and concentrate upon the cd. The more cd, the more distance you can see to.

If comparing two lights, for example, the one with the higher cd throws further.

After that, look at the lumens.

As a rule of thumb, if they have the same cd, but one has more lumens, the hot spot is USUALLY larger (same brightness, but a larger diameter beam spot).

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#### lednight

##### Member
Thank you for this in-depth conversation about Lux, Lumens and cd, wow! I started reading all the replies, but did not see my own question, for a smaller size light with good throw, should we look for a aspheric lense to minimize corona (wasted light?) Would this make a big difference in keeping the light concentrated?

#### Dave111

##### Member
Thanks a ton! Always had been scratching my head between those two terms.

#### 37Blenman

##### Active member
Thanks for the info, quite interesting!!

#### dmichael

##### New member
Very interesting. Thanks!!

#### msmith

##### New member
Much appreciated - was trying to figure this exact conversion out while shopping for my new lights! Thanks! :twothumbs