Ever the optimist, I keep hoping someone will make an LED bulb that doesn’t leave me wanting to run from the room or put on sunglasses while driving under LED Street Lights.
Folks who’ve been here a while will remember when I (we) discovered the spouse got insomnia when LED bulbs were running. That was attributed to them using a very blue light LED and “down shifting” it with other color phosphors, yet leaving a blue spike that causes a ‘reset’ of your biologial clock. Details in this link:
If Only the blue were gone, then the problem ought to go with it. So, when shopping at Costco, I saw a $10 package of 4 bulbs that claim a 2700 K color temperature (same as regular incandescent bulbs) I figured it was worth a shot. These are a very similar bulb though in a 2 pack and claiming 810 lumens where the ones I bought claim 800 lumens for the “60 W replacement” bulb of 8.8 Watts power consumption:
These are dimmable too.
So, OK, I gave them a try. Here’s what I’ve discovered.
The do dim nicely. Not quite as nice as an incandescent. They stay the same color, where the incandescent becomes more yellow, then orange and even somewhat red as they dim. There is also a ‘cut off’ where it just stops working that comes at not as dim a point as I sometimes like. But, ok, it’s good enough on the dimming for almost all purposes.
The package claims a CRI of 90+. The Color Rendering Index tells you if you will be getting “green eggs and ham” or other strange not quite right colors. Incandescents are essentially 100 (sunshine is and the bulbs are a cooler color temperature, but the eye knows how to correct for that). Horrible bulbs will have a CRI of 50 or 60. Low Pressure Sodium is monochromatic egg yolk yellow and range from 0 to 18 (but IMHO closer to zero for any I’ve seen). This page lists bulb types and their CRI:
Being at 90+ it ought to beat every fluorescent out there along with many other bulb types, only beaten by the incandescent, some metal / halide (think bright white lights at car dealer lots) and some very specialized “highest CRI” LED bulbs (that I’ve never seen in any store…)
Well, in my short testing they do have a very good CRI and colors did not appreciably shift perception when I swapped from incandescent back to the LED bulb (and back again).
By all objective measures this bulb seems to deliver what it is claimed to deliver. Clean, incandescent colored, high CRI light that’s dimmable.
So what’s the problem?
I can’t really explain the problem. When used as the only light source, my eyes feel “tight” and I’ve got an overall feeling of tension and unpleasantness. Not strong, just minor but there. Add in some incandescent, the annoyed feeling fads in proportion. I have three lamps in my office and two are on dimmers controlled at my desk. I could easily fade out one and ramp up the other and do various mixes.
Best explanation I can imagine is that (only as a crazy working hypothesis) the LED has a low persistence phosphor and there is some kind of just sub-perceptible “flicker” in the light. Something that, in theory, we can’t see as it’s a 60 Hz flicker; but where the effect of rapid swapping light for black has a subconscious effect on the nerves. This article per image rendering claims the limit (so also the threshold) is 60 Hz:
A topic that came up in the Udacity forum for my graphics MOOC is 240 Hz displays. Yes, there are 240 Hz displays, such as the Eizo Foris FG2421 monitor. My understanding is that 60 Hz is truly the limit of human perception. To quote Principles of Digital Image Synthesis (which you can now download for free):
The effect of temporal smoothing leads to the way we perceive light that blinks, or flickers. When the blinking is slow, we perceive the individual flashes of light. Above a certain rate, called the critical flicker frequency (or CFF), the flashes fuse together into a single continuous image. Far below that rate we see simply a series of still images, without an objectionable sense of near-continuity.
Under the best conditions, the CFF for a human is around 60 Hz .
Reference 389 is:
Robert Sekuler and Randolph Blake. Perception. Alfred A. Knopf, New York, 1985.
This book has been updated since 1985, the latest edition is from 2005. Wikipedia confirms this number of 60 Hz, with the special-case exception of the “phantom array effect”.
So does a light flickering full on and full off at 60 Hz cause some part of the visual nerves some angst? Perhaps only for some folks?
What I can say with certainty is that a printed card with various sizes of type on it and different colors was comfortable and trivial to read under a real 60 W incandescent. Under the LED I felt like it was “squirmy” somehow and found myself with a slight squint being applied. Just looking around the room, I felt a quiet unease. A kind of small tension. Now, long after I’ve turned it off and left only the incandescent on, my eyes still feel somewhat tired.
This has another possible. Something called pupillary flutter:
This is about the phosphors in fluorescent lights, but as LEDs also use phosphors, ought to still apply. Being an arc discharge, florescent tubes will have power flow both ways in the two halves of the AC cycle. An LED, being a diode, ought to only have 1/2 that. I don’t know if they wire the 4 elements in the bulb so that 2 work one half of the cycle and 2 the other. One would hope so, but if they need all 4 in series to get the desired voltage… well… It’s a big “who knows” where the Engineer who designed it may be the only who, who knows.
and Other Optical Issues
Flicker, Drowsiness, Migraines, Optical Sensitivity
This ranges from excess light to monitor flicker
Fluorescent lighting commonly causes problems, generally associated with a perception of flicker. These include drowsiness, headaches, migraines, and difficulty in concentration.
It’s Not Actually Flicker …
… It’s a Physiological (Neurological/Optical) Effect of Fluorescent Lighting.
It is very likely that what is perceived as optical flicker is not optical flicker at all. Rather, it is the effect of fluorescent light on the person’s own optical response.
Little is known about the actual cause. The most probable explanation is pupillary flutter caused by the spiked spectral pattern emitted by fluorescent lights.
In explanation, fluorescent lights rely on ultraviolet light being fluoresced down to visible light frequencies (hence “fluorescent”). The spectral light output is not continuous; rather it is a series of spikes. The spikes cause the pupil to alternately dilate and contract in response to red and blue spectral peaks in the light. The result is that the pupil erratically adjusts or “flutters”, known as “red-blue pupillary flicker” or “red-blue pupillary flutter”. Red-blue pupillary flicker is believed to be the cause of:
neurological effects such as headaches, migraines, drowsiness, general fatigue and malaise.
That “drowsiness, general fatigue and malaise” along with what feels like a headache trying to start but not quite making it and my eyes feeling tired is pretty much accurate.
I have no idea if this is only a “some folks” problem or a general “most folks but don’t connect it to the light bulbs” problem.
So, that said, I’m keeping one in a lamp in my office for further A/B and longer duration testing. I’ve also got one in a 3 bulb fixture over the kitchen table. One of that “1960s” era flying saucer shaped things with a turn switch in the middle to get 1, 2 or all 3 bulbs lit up at once. I have a Halogen in the 1 position, and the LED with a brighter CFL in the 2 & 3 positions. This will let me see if it’s OK when “diluted” of if that just moves the problem out to a longer run time.
So far I’m batting 1000 in LED Bulbs bothering me and the spouse in one way or another (or both). Street light LED bulbs have made driving at night a Royal Pain. I now have some amber “sun glasses” I wear when driving at night. They block most of the very blue color street lights. Low Pressure and High Pressure Sodium bulbs look quite nice though ;-) They do a dandy job of cutting back those obnoxious blue headlights Sylvania is pushing while letting my yellow fog lamps really light up the place for me when I want a little extra sometimes.
I’ve often wondered why folks think it is a feature to blind someone approaching you at 70 MPH… but it’s where car headlamps have gone now. Oh Well.
In conclusion, I’ve not yet found an LED bulb I can live with. These came close, and perhaps as part of a set of different bulbs lighting an area they can be “good enough”. OTOH – I had a rats-in-the-garage problem. Putting the old LED bulbs (bluer and harsher) in the garage and just leaving them on seems to have driven the critters away. I’ve got 2 x Glue Traps and 2 x spring/bail traps and no sign anything has touched them. Nor is more damage to boxes of stuff showing up. So at least they seem to repel other living things too ;-)
At $10 for 4, I’m not feeling too bummed about being out $10. I think I can find somewhere to put them where I won’t care too much. Maybe the porch / yard light… I’m not typically out there and it just runs all night… Has a CFL in it now but that could be changed.
IFF you are not sensitive to “flicker” and find other LED bulbs “Just Fine”, then these would be a very nice 2700 K dimmable option. They are clear glass so need a shade around them. Feit does sell frosted equivalent bulbs too. If flicker does bother you, and other LEDs are just not quite right to you, these will be no different; given my experience.
I’m very happy I laid in a “lifetime supply” of incandescent bulbs along with a good selection of CFLs back when PG&E (local electric company) was subsidizing CFLs. At 50 ¢ each, I bought about 8 years worth of various CFL sizes. Halogen bulbs continue to be sold in the hardware stores, so I’ve only put a small dent in my bulb inventory and then there is my “100 W bulb factory” 3-Way lamps. I buy 50-100-150 W 3-way bulbs and then mostly run them on 50 W for ambient background lighting. When the 50 W element burns out, I’m left with a nice 100 W bulb ;-) At any one time, about 1/4 of my lights are running on the “self made” 100 W bulbs (often with a dimmer – even a 5% to 10% dimming can make a bulb last years longer). So it’s not like I need to find a way to live with LED bulbs. It’s just that I’m a cheap SOB and really would like to use 9 W instead of 60 W… But I won’t compromise my comfort or sleep for 50 W of electricity…