It is a pity we are 'stuck' with relating brightness to wattage. If we used a proper definitive measure of brightness then manufacturers would have to be more honest. Brightness is something that can be properly measured with a calibrated instrument. Relating everything to a poor performing incandescent is not good science.
(Lux - Candela - Lumens - whatever)
Foot candles.
Foot Lamberts
Apostilbs
Millinits
Derek
magnitude and absolute magnitude. :)
Why? Would anyone still understand it? Are such complex topics taught in school science these days? Look at LED marketing, where they cheerfully use the right words, but in any order that makes the snake- oil sound best.
"Solid angle" is seemingly a concept that only lives in university- level maths these days, so I don't know how they're going to teach the difference between lumen and candela anyway.
The packaging of most (if not all) bulbs these days has a lumen value. You normally have to look for it though normally on the energy chart thingy or the bit that tells you the voltage and offcical base type, B22 etc.
Trouble is I don't know what 600 lumen compared to 700 is really like, all I can say is that 700 is brighter. You can use the number to do a better comparison between nominaly the same bulb though, one "60W equivalent" against another "60W equivalent" CFL for instance.
And how many lumens will a 700 lumen CFL give out after 6 months use?
Adam
Actually, I do look, but it's often not there. EU rules about labeling of lamps is going to change this. IIRC, it is going to require the lumen output to be the largest rating on the packaging. It will also require the energy efficiency rating, but manufacturers have managed to get the requirement to specify the power rating (Watts) removed. Apparently, we're all being confused by power ratings on lamps. If the power rating is still specified on packaging, it must be in a smaller typeface than the lumen output. If it is not specified, it must be available on the manufacturer's website.
Here's a table from an old manufacturer's datasheet, but GLS lamps haven't changed much in decades, so probably still correct:
GLS, Coiled coil, 240v, 1000hr
Watts Initial Lumens Average Lumens 40 410 390 60 700 665
100 1330 1260 150 2160 2075 2000hr (double life) are about 10% lower.Perl (frosted) used to be around 2% lower, when the frosting was etched with hydrofluoric acid. Due to H&S issues with hydrofluoric acid, perl bulbs switched to a powder dusting a few years ago, and I believe this is less efficient, but I don't have a figure. Softone, golfball, mushroom, and other decorative lamps usually have a painted coating, and this loses something nearer 20% of the light output, or even more if tinted.
People don't need to understand it, only to get used to it - how many actually understood what a 100W tungsten lamp was? Its "brightness"? Colour temperature? Angle? They were simply used to them and knew automatically that they could adjust the amount of lighting in a room by increasing or decreasing the wattage and roughly what they needed. The bulbs of any particular manufacturer were generally similar and therefore there was no problem replacing like for like. Rating CFLs by there wattage equivalence was a good idea, but badly implemented. If the ratings had shown equivalences to tungsten lamps that most people would have agreed with, and all manufacturers stuck to, then they'd have been useful. Instead they have taught people to be wary of believing manufacturers claims and ended up with a lot of people installing CFLs that give subjectively poor lighting that they are dissatisfied with.
SteveW
It's worse wrt non-rechargeable batteries. How the hell does "extra heavy duty" or "suitable for digital cameras" relate to an energy storage capacity?
#Paul
Not much point in simply requiring alkalines, and zinc cells to display their capacity in mAh, the internal resistance matters too compared to NiMH and NiCd
Andrew Gabriel :
What about those new-fangled PHP bulbs? :-)
Sorry, got perl on the brain at the moment.
Andrew Gabriel wibbled on Friday 27 November 2009 11:09
Good. If it were python, I'd have to come round with my chicken bones to cast out the evil
;->
Here in the US all packages at stores I go to have lumen and watt printed, If you want to compare Lumen hold a pack of incandesants and compare. I just figure Cfls output 75% more in my shopping. If you want to get technical to find the most efficient use you calculator and run LPW a Lumen Per Watt number. For new types I just use Watts and LPW as my guidline as some new cfls are 80% more efficient than standard incandesants.
Not sure exactly - but I remember that my old Fuji digital camera ran on AAs, and at the point it'd claim that the batteries were dead I could put them in something else and still get a lot more life out of them. I assume some classes of devices just fall over with part-discharged cells, and the "heavy duty" ones help address this.
cheers
Jules
Stick 1000 people in a room and get them all to rate the brightness of a particular bulb on a scale of 1-10? :-)
Problem I have is that brightness is only part of what makes a light 'good' for a particular application, so just saying that one bulb gives off as much light as another isn't necessarily good enough.
Same here, our apparently "dead" batteries usually go into clocks and continue to run for ages.
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