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LED-How to tell the real ligthing output of led lights?How to compare lighting p

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Bart_van_der_Wolf:

--- Quote from: BobShaw on January 22, 2016, 12:18:34 am ---Measure it with a light meter at say 2m. As Metallica would say, nothing else matters.

--- End quote ---

Hi Bob,

Sure, that will do, but a practical issue is that you first need to acquire such a LED light, and secondly unbox and mount in a reflector, before you can measure it. That obviously won't do for comparing advertised specs, before purchasing.

And as far as specs go, the LEDs will lose a percentage of their initial Lumen output capacity over time. Not all manufacturers specify that percentage.

Cheers,
Bart

BobShaw:

--- Quote from: BartvanderWolf on January 22, 2016, 03:26:55 am ---a practical issue is that you first need to acquire such a LED light, and secondly unbox and mount in a reflector, before you can measure it.

--- End quote ---
I disagree. If you are buying something that is important to your work, like lights, then you try before you buy. That's why there are still (a few) camera stores and suppliers. Buy cheap, buy thrice.
LED has yet to impress me, except for video, because you can't really use many modifiers. There are other posts her about strange colours, so it's a box of chocolates.

Bart_van_der_Wolf:

--- Quote from: BobShaw on January 23, 2016, 08:17:53 pm ---I disagree. If you are buying something that is important to your work, like lights, then you try before you buy.
--- End quote ---

Hi Bob,

While I agree in principle, it is in practice not possible to test all that is offered.


--- Quote ---LED has yet to impress me, except for video, because you can't really use many modifiers. There are other posts her about strange colours, so it's a box of chocolates.
--- End quote ---

I'm not impressed yet either. But the OP was more about comparing the the luminosity based on published specifications, rather than on colour. I would currently not choose LED for good color, but for other uses it may suffice.

Cheers,
Bart

Morgan_Moore:
I mainly do video now. Still struggling to match my vivitar 285, qflashes and elly set up.

Simply I am trying before buying.

I made a test which is 1/50 shutter 800ISO, what FStop when the light illuminates an area 8ft wide?

Some spotty lights have to be far back, some soft ones close.

Certainly try.. some i tried were very green

Also google Alan Roberts, lighting and you can read up on his tests of colour quality..

S

bjanes:

--- Quote from: haring on January 13, 2016, 09:50:47 am ---I am looking at several led light options. Obviously, one of the considerations is how much light the led panel emits.
Some companies list their products specifying out put via "lux"
http://www.adorama.com/fpvl500c.html
Others list Watt, W.
http://ikancorp.com/productdetail.php?id=998
Others use lumens...

My questions: How to measure/compare the lighting output of led lights? Is there a way to convert these numbers? All I want to know how much light these lights output so I can compare them.

--- End quote ---

What you are interested in is how much light from the lamp will fall on the subject: illuminance, which is measured as Lux (lumens/meter^20). On the Adorama site this is given under the specs tab. The falloff does not follow the inverse square law precisely, because the light is not a point source.

Bill

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