A guide to understanding new light-bulb terms, LEDs and more

A guide to understanding new light-bulb terms, LEDs and more
This undated photo provided by Kichler Lighting shows a kitchen with linear under cabinet lighting. (Kichler Lighting via AP)

Anyone who has stood in confusion in the light-bulb aisle (and that's most of us) knows that technology and the push to save energy are continuing to flip the script on home lighting options.

The good news is the new bulbs are much more efficient than old-school incandescents, and give designers the freedom to move beyond the standard bulb-lamp-fixture configuration.

"The new types of bulbs, LED in particular, let light-fixture designers create all kinds of lighting designs and fixture designs that they could never create before," says Karman Hotchkiss, executive editor of Decor magazine. "There are a lot of new shapes out there. There are a lot of really artistic interpretations of lighting, things like sparkle and effects that designers couldn't create with old-fashioned incandescent bulbs."

A primer on the latest in a changing technology:

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TERMS

For consumers, the big switch has been letting go of the concept of wattage, which is associated with brightness but actually measures energy use. Today's bulb brightness is measured in lumens. Old needed about 60 watts to produce 800 lumens. Compact fluorescents (CFLs) use around 15 watts to get to the same brightness, and LED (light-emitting diode) bulbs require only about 10 watts to get to 800 lumens.

Another major change is use of the color temperature scale based on heat, as measured in Kelvins, not Celsius or Fahrenheit degrees. The higher the heat, the cooler the color—which makes sense if you've ever looked at a flame and seen the blue at the hot center.

While we typically don't think in Kelvins, this is a more precise way to define the relative whiteness of a light source, says Joe Rey-Barreau, a Kentucky architect and lighting designer who serves as an educational consultant to the American Lighting Association.

If you see a bulb marked "daylight," you may be thinking about a warm afternoon light when the manufacturer means the much cooler color of the sky. A point of reference: The warm, orange light of the old incandescents burned at about 2,700K.

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PACKAGING

Manufacturers are still printing wattage-equivalent numbers on packaging for reference, and on the back you'll now find a required "Lighting Facts" information box—modeled after nutritional labels—listing lumens, estimated yearly energy cost, life span, light appearance and energy used.

Incandescent bulbs, by the way, haven't been banned. Manufacturers had to change the gas used inside them and make them more efficient. So, the old 100-watters are available as 72 watts; the 75-watt bulb is 52 watts.

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LEDs

The trending technology is the LED.

Introduced in the '60s, these bulbs used to be low-intensity and limited to red light. But recent developments have allowed for bright LEDs. The LEDs of the early 21st century tended to have a bluish cast, but LEDs now are available in a wide spectrum of colors.

Because LEDs use solid-state chip technology, they can be made very small and in various configurations. For instance, there are easily installed under-cabinet strip-lighting options, as well as lights for the kick-toe space near the floor, says Hotchkiss.

Tiny LEDs can be embedded into a fixture, such as a lamp itself, instead of the lamp having a holder for the bulb. There are even LEDs that resemble old-fashioned with a visible "filament."

LEDs cost more than conventional bulbs but last longer and use less energy, and prices are dropping, says Rey-Barreau.

For now, it's mostly lighting designers who are experimenting with the more extreme lighting possibilities of LEDs, such as installations that change color. But there are fun options for homeowners, too, Hotchkiss notes. GE, for instance, has a C-Life bulb that is Bluetooth-enabled and can be dimmed or turned off via a phone app.   


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Review: New light bulbs offer alternative to LEDs and CFLs

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Jun 15, 2016
Another major change is use of the color temperature scale based on heat, as measured in Kelvins, not Celsius or Fahrenheit degrees. ...While we typically don't think in Kelvins, this is a more precise way to define the relative whiteness of a light source, says Joe Rey-Barreau, a Kentucky architect and lighting designer who serves as an educational consultant to the American Lighting Association.
Utter nonsense. All temperature scales are merely linear transforms of each other. A temperature in Kelvin has exactly one equivalent temperature in Fahrenheit.

Jun 15, 2016
One of the consequences of the change is that it's no longer trivial to verify that a bulb is what it is advertised as.

Reason being that regular tungsten incandecent bulbs all work pretty much the same. If you got a 60 Watt bulb with a filament that lasts about 1,000 hours it's going to be equally bright from manufacturer to manufacturer due to laws of physics. You can trivially check with a kill-a-watt meter that the bulb draws roughly the claimed amount of power and be sure you got what you paid for.

With lumens as a measure of output, you would need an integrating sphere and a bunch of math to find out that the new cheap LED bulb isn't actually 800 lm but more like 600 lm - which means the consumers have no practical way to verify their purchase.

And sure enough, many of them don't deliver. It's just too easy to cheat because you can't tell the difference by eye unless you have a direct comparison that has the same light pattern and the same color temperature.

Jun 15, 2016
For example, I bought a LED lantern from a reputable manufacturer that advertised itself as 4 Watts and 300 lm. Fair enough - that would be 75 lm/W which is a plausible typical figure.

However, it also claimed 27 hours of light out of 4x D cell batteries. Here's the rub - a D cell has about 10 Watt-hours of energy at moderate draw and 40 Wh / 27 h = 1.5 Watts.

So the lantern could not have been 4 Watts or 300 lm, and both those figures were likely put there straight from the LED data sheet from the absolute maximum ratings. The actual lamp was de-rated to a much lower performance to achieve the advertised run time.

How do you tell just by looking at the lamp that it's not what it claims to be? You can't see lumens.

Jun 15, 2016
Also, some of the cheapest LED bulbs have nothing but a resistor for ballast, so they blink like a fast stroboscope. That's also something you can't read off of the packaging.

I'm talking about these things: https://www.maxxi...EW22.jpg

It should work in theory, because half the diodes in the bulb are off while the other half are on at different half-cycles of the mains frequency, so the blinking should be well beyond the persistence of vision (100 or 120 Hz) but because the diodes are pointing in different directions inside the bulb, the light pattern from the bulb changes at 50 or 60 Hz and you can clearly see it.


Jun 15, 2016
Damn, Eikka, you sure are long winded.
I take it, for one reason or another, you don't get out much.

Jun 15, 2016
Thank you Eikka for giving us number that show you know nothing of what you're talking about.

1) D cells have 20 Wh not 10.... minimum. You can do better.
2) 4 D cells may be able to be discharged further depending on the dropout of the device. Yes I know the dropout is fast, but the point where discharged is declared can vary depending on device. They always use the best batteries when advertising. Remember it's UP TO 27h.
3) Every single other bulb I have replaced has been brighter with a LED equivalent watt. The most obvious of these were GU10 bulbs. 50W halogen or 4 Watt LED. The LED was actually brighter to everyone I showed it to.
4) AC powered LED lights do not use a simple resistor ballast. They will use a tiny transformer, a bridge rectifier and a small capacitor.
source: https://www.youtu...aLgDsYVk

Jun 16, 2016
1) D cells have 20 Wh not 10.... minimum. You can do better.


Only at very small currents around 30 milliamps or less. At larger currents the practical capacity drops to half due to the high internal resistance of alkaline batteries, and because of Peukert's law.

I have done some engineering in trying to develop an emergency lantern that consists of a boost converter that goes between a bunch of regular alkaline D cells (because of their long shelf-life) and an ordinary small 5-7 Watt compact fluorescent light, and the power the cells can give out is very limited. The theoretical maximum capacity of four D cells is indeed about 100 Wh which would give you 3.7 Watts, but the practical maximum is half that.

Every single other bulb I have replaced has been brighter with a LED equivalent watt.


That's largely because the LED is highly directional. You shine it in someone's eye and they will say it's bright.

Jun 16, 2016
AC powered LED lights do not use a simple resistor ballast. They will use a tiny transformer, a bridge rectifier and a small capacitor.


There's nothing that says they can't. The simplest way to make a LED bulb is to use enough diodes that their combined series forward voltage drop falls slightly short of the line voltage, and add a resistor to limit the current. It's simple, effective, and fairly efficient.

And I measured the light output from my bulb and it pulses from zero to full brightness with every other pulse changing in relative amplitude depending on the direction where I place the meter, indicating that the output comes from alternating between two strings of LEDs on the two half-cycles of AC which wouldn't make sense if it was smoothed with a rectifier and a capacitor.

I've yet to pull the bulb apart because I need it.

Jun 16, 2016
Remember it's UP TO 27h.


And I did test that as well, and it does go for at least 27 hours before it blinks out. I'd have to break the lantern to get access to all the bits to measure the actual current draw from the batteries, but from what I've tested those batteries do not give out more than 10 Wh.

Point being: caveat emptor. This is a new technology and consumer advocacy groups haven't yet gotten their teeth on it, and people in general have little understanding of how it works, so all the manufacturers cheat. Some more, some less.

Jun 16, 2016
This video shows perfectly the mad amount of flicker from these bulbs
https://www.youtu...hdAz9pc4

The camera captures it better than the eye, but the eye sees the flicker in moving objects such as moving your hand underneath the light. That makes it very irritating to use as a working light, and in machine shops it can potentially be very dangerous because of the stroboscopic effect on rotating tools.

And when he pulls the bulb apart, turns out - no smoothing capacitor, no transformer - there's a small IC and that acts as a thermal fuse and a current limiter. That's a ~£7 bulb while mine was 2.99 - even cheaper.

Also, a second point on LED brightness: when the manufacturer has chosen not to de-rate the LEDs or has put them in casings with less than optimal heat dissapation, they quickly grow dim. The first 10 seconds they shine bright and then drop, and the heat eventually causes a permanent drop in output.

Jun 16, 2016
And in fact, as with CFLs, LED bulb lifetime is measured not to the point where the diode fails but to the point where it has lost 30% of its nominal output as a typical figure. Some manufacturers - again cheaters - report it to 50% drop or some other figure that is convenient to them.

There's a lot of cheating going on because LED datasheets rate the nominal output at an industry standard junction temperature - that is the internal temperature of the diode - of 25 C which never happens in real world use. The datasheet figures hold true for about the first 10 seconds after you turn the light on, and then the output drops.

That is one reason why the numbers on the packaging and the actual brightness of the lamp differ. Some Chinese dude writing the documentation takes a look at the data sheet and goes "This is a 4 Watt 300 lm diode, so I'll put 300 lm on the packaging" and on it goes.


Jun 16, 2016
And as we saw from the video, the LED bulb starts off at 7.3 Watts and drops to around 5 Watts after it warms up, which is another effect and reason why people can mistakenly identify these bulbs as brighter - because they are - for a bit.

Jun 19, 2016
What's carefully ignored is the reaction to the form of LED light. Blackbody radiators have smooth intensity curves over wavelengths, with the wavelength at maximum intensity deciding the color. LED bulbs are at 0 at 4000 and 8000 angstroms, they have maxima at about 4500 and 6150, and a minimum at about 4800 and the strength of the maxima and minimum "defines" the "color". But human eyes are designed as black body radiation receivers. People will be thinking there is "something missing" and not knowing what it is. And that can lead to everything from eyestrain up to mental distress! And nobody's explaining this to them!

Jun 19, 2016
I've been using dimmable and indirect lighting sources for decades; I see no reason to put up with lights shining in my eyes in my home.

I haven't had a light bulb go out in my home in over two years, and my electrical energy consumption went down by an order of magnitude when I stopped using standard incandescent bulbs twenty years ago. My kitchen is lit with 15W fluorescent lights under all the cabinets over the counters. About once a week I have to fire up the big 40Wx4 fluorescents to clean the floor or the 300W dimmer-equipped incandescent array over the sink to clean it.

If I need intense light I have it; most times I elect to use the dimmer and save 70% or or the under-cabinet fluorescents and save 90%.

Why have a light shining in your eyes when what you need is light shining on what you're trying to see? This is duhhh ummm.

@Eikka fails to understand how light works.

Jun 19, 2016
And as we saw from the video, the LED bulb starts off at 7.3 Watts and drops to around 5 Watts after it warms up, which is another effect and reason why people can mistakenly identify these bulbs as brighter - because they are - for a bit.
@Eikka fails to understand the difference between light intensity and power consumption.

Or obfuscates it.

Seriously, dude, stop posing as an expert when you don't understand the difference between lumens and watts.

Jun 19, 2016
I agree with Eikka that light quality has not been given the weight that it should. But how many of us remember that also old passively ballasted tubes also turn on and off at twice the mains frequency, which makes 100 or 120 Hz flicker. In the newer ones this flicker is at 20 kHz or higher, which no-one should notice. Bu this flicker frequency should also be mentioned in light source packaging. And also how continuous the light spectra is. Just mentioning CRI as a single figure does not really explain the real effect.

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