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

[haring]

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"
Dead Link Removed
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.

 

[Gerald C Koch]

To convert lumens to lux

http://www.rapidtables.com/calc/light/how-lumen-to-lux.htm

 

[wiltw]

Watts is only a consumption of electricity...it has no direct bearing on how much light it produces. To prove this failure of equivalency to yourself, go to the hardware store and look at 60 Watt bulbs of different models and manufacturers, and compare the Lumen output...seldom do any two brand/models output same light!
For example, going to one on-line bulb vendor, they list

• seven 60W incandescent bulbs all with different lumen ratings, from 420 - 660 lumens.
• they also list 60W equivalent LED, and depending upon the color temperature of the bulb, output of light is 350 - 825 lumens!

...so we obviously cannot jump to ANY conclusion about 'equivalence' in light output!

 

[gone]

I tend to think that wiltw is correct. Even if you know how bright the bulb should be, a lot depends on placement in the darkroom. It's simple enough to restrict the light, even w/ a simple shade, or angle it to the ceiling and bounce it back. The only way I've found to figure this out is by using the least amount of light that I can get by on to work, and then doing a safelight test w/ paper to make sure it's not going to lead to fogging.

 

[MattKing]

I expect that the OP is asking in relation to light sources for exposing film, rather than for darkroom lights.

I note that the specifications for the second example linked to by the OP include information about lumens, lux and foot-candles, all of which are related to light intensity.

Watts are certainly relevant to electrical power requirements.

 

[Les Sarile]

Direct comparison is the best way but my recent experience tells me that there is a direct correlation between wattage and amount of light. If so then I would expect the Adorama Flashpoint's 42watts to provide more light then the ikan ID508-v2's 30watts.

I've been recently playing with LED lighting and started by converting my old Maglites to use LEDs, then I bought some native LED flashlights and finally built my own 100 watt LED portable light.

Here is a simple comparison of the amount of light my DIY 100 watt light can provide. A scene lit by a 100 watt equivalent daylight balanced CFL gave me a meter reading of 1/8 shutter speed while my DIY 100 watt LED allowed me a shutter speed of 1/320.

A constant LED light source has no sync speed issues and runs considerably cooler than an alternate light source providing an equivalent amount of light. I made it portable by using a lithium battery. The lithium battery is much lighter and provides more power than the SLA battery I used initially.

The 100 watt LED is capable of about 8500 lumens and makes a great flashlight providing much more light than my car's headlights. BTW, there are now even higher powered LEDs of 250 and 500 watts but those are currently pretty expensive.

 

[wildbill]

I wouldn't necessarily trust the photometrics of these cheap panels. Same goes for the color temp. Most of them (including the high end brands) need some green correction.
The two examples you linked to are similar but one's wearing a diffusion panel. Most of the professional led panels larger than the standard 1x1 LitePanel. To give you an idea look at Arri and Kino Flo's newest fixtures which have a heavy plastic diffuser over the led's. This is because as a direct source, they are a pretty hard source.

 

[calebarchie]

I strongly suggest you get your answers from more viable sources. An electronics/lighting forum or books etc NOT a photo forum.

 

[Les Sarile]

I strongly suggest you get your answers from more viable sources. An electronics/lighting forum or books etc NOT a photo forum.

If his end goal is to use it for photography, this is actually a more appropriate forum. I visit the lighting forums and although they review the various technicalities of lighting systems, they don't do it from the perspective of light quality which is more useful in photography.

 

[calebarchie]

But this is not about CRI of LEDs, let your response serve as an example of why I say this.

 

[Les Sarile]

But this is not about CRI of LEDs, let your response serve as an example of why I say this.

Exactly right, the OP simply asked, "Obviously, one of the considerations is how much light the led panel emits." and not at all about CRI as it pertains to photographic use. He wants a simplification of how to compare two variations of measurement of light sources to which I provided a very simplified response based on what I have observed is the lowest common denominator among LED lights - watts.

 

[wildbill]

But this is not about CRI of LEDs, let your response serve as an example of why I say this.

wow.
NO IT'S NOT ABOUT CRI.
I read the op's post before I typed. My answer came from many years of hands on experience using all types of lighting units including LED units.

 

[M Carter]

CRI is important for color shooting; but manufacturer's CRI listings are often, umm, optimistic - and CRI isn't of total importance. I have daylight fixtures around 80 CRI that can be gelled to look great (but I consider gelling to be good if they're 1/2 or 1/8 level gels so you don't kill all your output. Though I have a 575 HMI that needs 1/2 CTO - it's still bright as hell).

LEDs are the big new kid on the block thing, but you have to spend some big bucks to get decent output. All the kids on the filmmaker forums that got their first DSLR that shoots video for their back yard zombie flick are like "should I buy this LED", and the specs for some $300 unit show its output to be equal to one 55w biax flo tube. Not one fixture but one tube. (About 2800 lumens)

So I say "buy a quad biax for under $300" and get 4 times the output". EBay is packed with 500-1k fresnels for under a hundred bucks. Tons of open faced fixtures out there for bounce or diffusion, too.

If you're doing B&W and want some output, get some strobes or tungsten, unless you shoot in situations where you need batteries. LEDs are still kinda sucky technology (as far as getting the lumens you need to affordably shoot in a space with windows or want to shoot with low ISOs) until you can spend $1k for a fixture. (Unless you need battery power in which case they're better than hauling a generator or "no lights at all".) But I've shot commercially for decades, still do, and have yet to be where I couldn't run an extension cord. But I don't do local news, where LEDs could rock I suppose. I usually have at least a few minutes setup time for commercial gigs; for corporate interviews I tell them 30 minutes. And it's usually a quad biax with diffusion or a 400 HID softbox setup (5600k and 33,000 lumens). If you clicked on one of the current popular LEDs in those settings, you'd barely see the extra lumens.

As far as the original post - if you want to know output, it's really about how you shoot - include diffusion and distance and compare it to your current setup for the same look. How many stops more or less do you get? It can be tough to suss that out with just the sales specs.