LED nerds. Any help with Lumens? How are they measured?

frascati

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Jd74vbd.jpg
.

I just received some SORAA MR16 bulbs in the mail.
SM16-09-25D-830-H1
I paid a premium price for these based on the 725LM @ 25 degree brightness.
The specification sheet at SORAA and the specifications listed at the distributor that I purchased them from confirm this rating.
However when the bulbs arrived, the sealed OEM packaging lists the correct bulb, SM16-09-25D-830-H1, and the bulbs
within the packages confirmed as the correct bulbs...
But the package specs say "90 degree Lumens: 685LM.
https://pasteboard.co/Jd74vbd.jpg
Jd74vbd.jpg

Is this correct?
 

StarHalo

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You need at least a 10% difference in output before you can discern any difference by the eye, so a 685 and 725 lumen emitter side-by-side would appear identical.
 

frascati

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What I was hoping someone might clarify for me, enLIGHTEN me on:), was the significance of beam spread, degree, in the lumens rating. Is it significant?
725Lm at 25 degrees. 685Lm at 90 degrees? This might explain the difference in Lm rating on the bulb, if true.

Did the pasteboard image link open for you? My work computer is URL filtered and won't show it.

And sorry for the bad pun...
 

StarHalo

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Joined
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10,927
Location
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What I was hoping someone might clarify for me, enLIGHTEN me on:), was the significance of beam spread, degree, in the lumens rating. Is it significant?
725Lm at 25 degrees. 685Lm at 90 degrees? This might explain the difference in Lm rating on the bulb, if true.

I'm not previously aware of the use of a degree rating to measure lumens; typically if you account for the beam shape of the emitter, it's to express in lux/cp what the throw of the beam is, not the output. Otherwise, if you're going to provide a lumen rating, especially for a bare emitter, it needs to be a gross overall lumens number not muddled by how the light is projected.
 

frascati

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Joined
Feb 28, 2012
Messages
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I'm not previously aware of the use of a degree rating to measure lumens; typically if you account for the beam shape of the emitter, it's to express in lux/cp what the throw of the beam is, not the output. Otherwise, if you're going to provide a lumen rating, especially for a bare emitter, it needs to be a gross overall lumens number not muddled by how the light is projected.

"..especially for a bare emitter..."
Except that the MR16 is not a bare emitter... if I understand the terminology correctly.
This is an image of the Soraa Mr16.
71KnK2hKTGL._AC_SY355_.jpg


It's a 'bare emitter' housed in a 25degree spot reflector.
The .pdf spec sheet from Soraa lists it as follows..

3000KHalogen
Equivalent
WattsBeamLumensCBCPModel #
Brilliant HL
9W
CRI 90
R9 50
Indoor/Outdoor
759257253730SM16-09-25D-830-H108738

And this is the packaging the bulb arrived in.
https://pasteboard.co/Jd74vbd.jpg

It's actually a pretty damn amazing little bulb. 700(approx) lumens 25 degree spot with great color rendering. 9watts/12vac. I'm using a pair of them
leading the way through the night on 1984 Puch moped. The magneto puts out 3 to 18vac with just enough wattage to light them fully. They handle
the ragged voltage and current spikes from the ancient magneto superbly. I've had a less bright pair of these MR16s, philips brand, on my three mopeds
for 10 years now without fail and no noticeable loss of brightness.
Jd74vbd.jpg

Jd74vbd.jpg
 
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