Typical 50W GU10 halogens and data sheet

[LabudMoj]

Hi,
I'm trying to interpret a bulb's data sheet. It's a 50W GU10 halogen:
http://www.osram.com/osram_com/prod...m-halopar/osram-halopar-16-gu10gz10/index.jsp

Elsewhere, I've read that typically this type outputs >800 lumens, while in this specs it claims it's only 300 lumens? I am not sure if the angle of 90° for which this is specified plays any part in this discrepancy, as I imagine that due to the shape of this bulb this would be about the angle where the entirety of the light flow ends up.
Is this some weird industry norm that is not much helpful for end users, or I am just not reading it right?! Any attempt at explanation will be much appreciated!

 

[knowall]

HISTORYMAN ……..move on led

 

[LabudMoj]

knowall, spot on - that's exactly what I'm actually doing! Seriously, I already have a couple of GU10 LEDs, of which the brightest ones are rated at 540 lumens, now just trying to figure out how do they compare to halogen ones. It just seems it's a bit of wild west with the specs, so it's hard to compare like with likes. Any definitive resource/comparison site you know about?

 

[knowall]

Philips - are the most accurate comparison. NEWAGEMAN!

KA

 

[DaftPunk]

The luminous intenstity of lamps is generally measured at 1 meter from the lamp, so due to the wider spread, a 90 degree lamp will show less lumens than a 36 degree lamp even though they are producing the same amount of light.

 

[LabudMoj]

Thanks for the reply, DaftPunk. I think I get it now although what you wrote is slightly wrong. Mind that this lamp is a 36deg one, not 90deg, that's just the angle for which the luminous flux (lumens) is specified for!

My understanding: beam angle is defined as an angle where the light intensity drops to half than at its maximum. If the centre intensity is 1000 cd, then the angle where the intensity is 500 cd is your beam angle. That means that with the same centre intensity the wider beam angle will probably give out more lumens (higher overall brightness). This I guess depends on the light's source intensity diagram, but I think it's safe to take this as a rule of thumb.

I had failed to realise that all the LEDs I have are of wider beams, at 120 deg., so at the same lumens figure, they are not as intense in the centre as the halogen ones. Seems that sometimes candelas and lumens get mixed up in some comparisons, so the value of >800 lumens I keep reading about for halogens should actually be candelas, like on that data sheet where it says 900 cd! Well, at least that's my theory now.

 

[ericmark]

I swapped CFL for LED and reading lumin output should have been darker by 1/3 yet it was in fact very much brighter. It would seem the spec for lumin is flawed as a result it's just suck it and see.

I had two GU10 lamps either side of bed on the wall to read with 35W tungsten was good enough but 11W cold cathode was not. The 11W cold cathode gave about the same output at the 0.58W LED you could just about read with them but not with ease. Swapped to a 3W LED and that is nearly as bright on the page as the 50W tungsten.

 

[Taylortwocities]

You may find this useful http://www.lightingfacts.com/downloads/performance_scale.pdf
It is a tool to help evaluate LED products to determine whether they are appropriate for a given application.