Are LED bulbs becoming less efficient?

[ericmark]

I have just gone out to buy bigger bulbs as wife complaining old ones not bright enough, SES so looked in local shop and 5.6W and 470 lumen were largest I could find with SES fitting, so 84 lumen per watt, however the small 300W tube replacement at 5.6W was 560 lumen, 100 lumen per watt.

Looking at bulb they don't look brighter, but the room does, took out 3 x 3W and 2 x 1.6W no lumen marked on them. The bulbs must be the originals from Lidi when I first tried LED they replaced 8W Philips CFL and at the time looked far brighter, as to if really brighter or higher kelvin hard to say, however we commented when first replaced the 2 year old CFL on how much brighter.

So have our eyes got worse, or has the bulb become dimmer, don't think latter or the new LED would have again looked very bright, and they don't. So is LED light damaging our eyes?

 

[JohnD]

dimmable bulbs have lower efficiency than simple ones.

 

[Astra99]

Also, warm white (2700-3000K) have a lower lumens output than the equivalent cool/daylight white (6400K)

 

[flameport]

Some manufacturers blatantly lie when stating the light output. Some others don't state anything, and then there is the 'equivalent to X watts incandescent' which is entirely meaningless.
Colour has a massive impact on perceived brightness, both in the colour temperature and the CRI.
Human eyes in general are useless at accurately perceiving light levels. They adjust continually to suit whatever illumination is available.

 

[JohnW2]

Some manufacturers blatantly lie when stating the light output. Some others don't state anything, and then there is the 'equivalent to X watts incandescent' which is entirely meaningless. ... Colour has a massive impact on perceived brightness, both in the colour temperature and the CRI.
Human eyes in general are useless at accurately perceiving light levels. They adjust continually to suit whatever illumination is available.

The whole situation is, indeed, potentially very confusing (at least for me), not the least because I'm not at all clear as to what it is that manufacturers are reporting.

Radiant flux and luminous flux (both measured in lumens) are two different things. Radiant flux is the total of emissions across all wavelengths - and hence, I suppose, in terms of physics is the quantity most likely to relate to supplied electrical power (as in "lumens/watt"). Luminous flux is adjusted according to the human eye's different sensitivity to different wavelengths of light. Hence, two different sources with the same power input and same radiant flux could have very different perceived brightnesses (with 'efficiency' also measured in lumens/watt) if the wavelengths (i.e. colour) were appreciably different. What I don't know id which type of flux (or flux/watt) manufacturers are reporting, or which type people are talking about when they mention 'lumens/watt' her (and elsewhere)!

Kind Regards, John

 

[ban-all-sheds]

What I don't know id which type of flux (or flux/watt) manufacturers are reporting

That which casts their product in the most favourable bucket of lumens.

 

[ericmark]

The bulbs are not dimmable, and when I went to buy them, both the 3W and 5.6W bulbs claimed to be equal to 40W, when we bought house we had two bulbs in the room at 100W each, this was changed for fittings taking 3 bulbs and some times we used 60W and some times 40W and when the CFL came out used 11W which looked rotten, so changed for 5 lamp units each with 5 bulbs also moving from BA22d to E14 bases, using 8W CFL in a globe shape, so dropping from original 200W to now 80W in the room. But that 80W was no where as bright as original 200W and the bulbs were expensive. When Lidi started doing 1.6W candle bulbs I got two to try, it just happened the 8W CFL failed so used temporary to replace them, I was rather impressed, so when Lidi did some 3W versions removed the last of the CFL still working and fitted all LED in the room, very pleased, but over time they seemed to get dimmer.

So HomeBargains were doing 5W globe so swapped them, using the old bulbs in mother's house as room smaller, we have now moved to that house, so wanted to change to larger bulbs, swapped 5 with old house, brighter but not by much, so thought maybe over time they were getting dimmer, so popped into B&M Bargains and picked up 6 candle bulbs at 5.6W each, largest bulb I could find with a E14 base.

The old 5W bulbs in one set of 5 lamps seems no different to new 5.6W in other set of 5 lamps, so it would seem they have not dimmed with age, the increase 11.8W to 28W has made the room brighter, but not really by that much, so room has moved from a single 100W bulb to 53W LED, so halved to total bulb size from original, but for the packets in the shop to claim 3W = 40W seems to be wishful thinking, in the old days with a 100 ASA film and a f2 lens on camera I could take pictures at 1/30 second, today my camera only has a f5.6 lens, but can set to 800 ISO (same as old ASA) but the speed is down to 1/20 second, can get away with that with built in anti-shake, but it seems the room is no brighter than when using a single 100W bulb.