T8 LED 4' Tube Lights

Keep your receipts.
110 Lumens / watt is outstanding, although the advert that says 'half the watts as fluorescent' is misleading since the newer fluorescent bulbs are in 70 - 80 lumen/watt range IIRC.
Addendum: Yep, these are 90 lumens/watt.

I love LED lights regardless. Enjoy !

 

I have installed 26 T-8 /18/20/23 watt 4 ft LED tubes in various areas of my home. Replacing 40 watt fluorescent and I put one LED tube in to replace two fluorescent and have brighter lights. Some of my tubes are 35-4000 K and some 5000 and some 6500 K. Bought at DHGate (china) and some from ECO Energy LED's in Florida. Great lights all. Rewired fixtures, easy, removing the ballast.

 

As you posted earlier, people are comparing to their multi-year old fluorescent bulbs. As far as spectral sensitivity is concerned, I thought the lumen measurement took that into account.

 

This is a very important feature of LEDs. The directional output can put much more of the light directly on the intended target, without having to deal with reflector inefficiencies.

As Sagebrush mentioned, this should already be accounted for in the lumen definition.

FWIW, the theoretical efficiency limit should be 683 lumens/watt for a pure green light at 555 nm. White light should be capped at 250-350 lumens/watt, depending on what approximations of 'white' are applied.
Luminous efficacy - Wikipedia, the free encyclopedia
Luminosity function - Wikipedia, the free encyclopedia

 

Without knowing any details about this spectroscope, and with looking at the bizarre pattern, smearing and non-monotonic spread of the colors, I am unable to trust the 'no gaps' claim of this particular marketing piece. Show me a spectrum with a similar type of spectroscope used in the HPS image.

Yes, I do believe that LED spectra can be superior to common fluorescent spectra. But this particular puff piece comparing an unknown LED to HPS and LPS (not fluorescent) doesn't give me a good feeling of being an unbiased comparison of LED to fluorescent.

 

Let me return the favor:
Lumen

 

Then perhaps I have been under the wrong impression that LEDs have a lot of room to improve in efficiency since ~ 30% already sounds pretty good. I've been using ~ 600 lumens/watt as the maximum without realizing it was the peak sensitivity wavelength.

On a tangent, it is tantalizing to wonder why the human eye evolved to maximum sensitivity to green. Is sunlight (or moonlight for that matter) more green than red or blue ? Or does the environment tend to reflect more green light ?

 

Haven't read through iplug's link yet, but the reason for the LEDs appearing brighter revolves around Mesopic vision - Wikipedia, the free encyclopedia. Photopic vision is what our eyes are operating under when out in the day. The cones, color receptors, of the eye are doing all the work at this time. In near dark, the light sensitive rods are the only ones able to operate. In lighting conditions between those two extremes, the rods and cones are working together. "The traditional method of measuring light assumes photopic vision and is often a poor predictor of how a person sees at night." Since lumen measurement assumes just the cones working, it can be off from what people actually perceive with interior lighting since the their rods are also working. With the rods being more sensitive to light intensity, their input to the cones could make a light source appear brighter than what the lumen measurement would state.

As to the specific of LED to fluorescent tube, I would think the fluorescent's age plays a big part in the LED appearing brighter. Perhaps this no longer applies to current tubes, but it used be that you should replace the tubes on plant and reef aquariums after a year, because of light output loss. They still looked bright, but the loss is a slow steady decline over time that just goes unnoticed.

 

I don't understand either part of this sentence.

Perhaps I am wrong, but I think of cones as rods with a filter that lets in only red, green or blue wavelengths for red, green and blue cones respectively.

 

This error of ignoring the age of the fluorescent bulb when comparing to a new LED caught me for years when I would buy a new notebook computer. I would be amazed at how much much better and brighter my new notebook screen was compared to the old one and concluded that technology has progressed dramatically. It took me years to realize that I was simply enjoying an un-aged screen.

 

If the rods were merely cones without filters, why would we need separate rods to see in low light? Many nocturnal animals have little to no cones in their retina.
If the filters cut down the light getting to the cones, then the rods would still have an amplifying effect on how intense light appears when working with the rods? The rods a stimulated at a lower threshold light intensity than the cones are.

Going with the filter analogy, in midday sunlight, only input from the cones is used by the brain. The three different color filters act like a pair of sunglasses on the entire viewed scene as the cones are each only seeing a portion of the spectrum reflected to the eye. As evening comes on, the rods start coming into play. Since they are stimulated by the entire spectrum, they effective sunglass tinting is reduced. Until it gets dark enough that the cones can't see anymore, the filters are gone, and the rods are struggling to make an image.

The Wikipedia article didn't mention anything on perceived brightness being higher under dimmer light sources, but it mention the shift in perceived spectrum of the eye. The differing perception of different colors may lead to a mental illusion of increased brightness.
Purkinje effect - Wikipedia, the free encyclopedia

A simulation of the same flower viewed under bright light, low light, and night by the human eye.
Another factor to consider is that the retina can only hold so many rods and cones. Under bright light and near darkness, only one or the other is working. So a person may be seeing something with only about half their light receptors firing. Under lower light conditions, the two are working together. Thus more individual receptors supplying info to the brain.

The same applies to tires. A cheap retread will seem amazing compared to the worn, possibly bald, tires they replaced.
This why my bet is on the tubes being old for most of the seen difference. Not only do they dim, but can also shift to a warmer, yellower spectrum. The sodium lamps in iplug's link are also a yellow color. Going from that to a cooler, full spectrum light, the old lights will look dimmer, even if the lumen output is close between them.

 

No, the cones are not simply filtered rods. The rods are the dim light receptors, and are not part of the bright lumen response curves. The cones don't have filters, just something like dyes with different color responses.

I suspect this particular color sensitivity difference is more of a chemistry issue than an evolutionary issue.

Different critters have much different color vision. Birds and reptiles typically have 4 color vision (red, green, blue, and UV). In addition, their cones really do have color filters, in the form of oil drops on top. And even more, their red and green sensitivity peaks are more widely separated than in humans. With all these differences combined, their eyes produce much more vivid color vision than our eyes. I have no idea how well their brains can exploit that, it might simply enable useful color vision with far less brain post-processing power.

Mammals lost the oil drop filters and two of the colors (red and UV). Humans and some other primates reinvented the red, but with a much smaller separation between red and green. There are very many slight variations of the red dye, plus a significant fraction of genes where the 'red' cone is just given a copy of the 'green' dye, which is why many people are red-green colorblind. And this gene is located on the X chromosome, which is why red-green colorblindness is far more common in males (only one chance to get a true red color receptor) than in females (two chances to get red).

 

It also may explain why women can see more shades of red.

And I can't skip mentioning the mantis shrimp. They don't have 3 or 4 different cones, but twelve. With vision into the infrared and ultraviolet, they can spot prey and predators that would be virtually invisible to us.

 

Do you have an informative link ? I looked a little and came up empty, although if memory serves I may have read a while ago that the mechanism behind different color cone sensitivity has a quantum basis and results in a functional filter. In bright light the rods are mostly all activated, so there is no field definition.

 

That will be some women, not all of them, maybe not even most of them. The enhanced red vision would require two significantly different versions of the red gene. I haven't seen anything indicating what fraction of females have enhanced red discrimination. It probably varies significantly among ethnic groups. And I'd speculate that it would be more common among 'mixed breed' people, pairing red genes from differing ethnic groups.

But I don't recall seeing anything definitive about whether or not this 'enhanced' red is expressed usefully. Some other research comparing people with vastly different proportions of color cones discovered little perceptual difference. The post-processing in the brain might be making up for it.