I'll have to dig for the rod vs cone difference, my info on that predates the web. The 4 color vision info of birds and reptiles came from a SciAm article some years back, but I've seen more since on the web. Quantum basis for different color cone sensitivity? That seems like another way of describing dyes and chemistry. In bright light, I do believe the rods are saturated, which of course leaves little or no definition.
Oops, left out the some. Yes it ultimately comes down to what the brain does with the data from the eyes. The only reason we don't see the eldritch horrors walking among us is because the brain is protecting itself from severe shock. As why a light of a lower lumen might appear brighter than the lumen rating is that the lumen rating is a measurement based upon our photopic, cone only, vision. In an environment were the lighting isn't bright enough for photopic vision. the lumen measurement may not be the accurate one. Of course there are other factors at play that may have bigger role. But hey, we are talking about individuals brains at work here. For years I wondered what the big deal was about stink bugs, and last year it sank in that I simply couldn't smell them.
This is interesting: http://www.lpi.usra.edu/meetings/lpsc2003/pdf/1269.pdf The moon absorbs more of the lower wavelength radiation. I read elsewhere that some 2/3rds of human retinal cones are red sensitive. Not making sense yet (why the lumen measurement is weighted towards the green spectrum).
^ what Trollbait said. Agree, they are probably shilling to push their product and probably left out some important methodology/specification details in their spectral comparisons. I would bet they were comparing high CRI LEDs (table and/or spectral graph) to the worst fluorescents (table data) and HPS (spectrum) and they were not consistent with how the two spectra were graphed. Only meant to put this up for the background on scotopic lumens and that generally LEDs can be favorable in this regard, and just grabbed what came up first on google. I brought this up as I have read about it before from sources that had nothing to sell. I also did a quick search to see if I could find Lawrence Berkley Laboratory papers on this, since they were referenced, but no luck.
Here's my choice for the garage - I think I already posed these bad boys on another thread, but what the heck. I defy ANYone to beat these Costco prices - $39 bucks !! check 'em out; right now we have 3 pair of the 6' fluorescent tubes. Once these 60 watt pigs burn out, this is how we're gona roll.
Also from that site, "The cones are less sensitive to light than the rods, as shown a typical day-night comparison. The daylight vision (cone vision) adapts much more rapidly to changing light levels, adjusting to a change like coming indoors out of sunlight in a few seconds. Like all neurons, the cones fire to produce an electrical impulse on the nerve fiber and then must reset to fire again. The light adaption is thought to occur by adjusting this reset time." So entering an area in which the light level is low enough for the brain to start using input from the rods, a person's vision will be more sensitive to the local light than the measured lumens would imply. Our Costco doesn't have those. Though, if you already have flourescent tube fixtures in place, I suggest looking into the retrofit LED tubes. There are even ones that work with the fluorescent ballast for those not comfortable doing the wiring to bypass it.
My understanding of the lumen unit is power per time*area, corrected for relative wavelength sensitivity. You seem to be presuming absolute sensitivity which I think is wrong; but even if not, wouldn't that simply be a fudge factor true for both bulbs ?
Did a little Wikipedia surfing. Lumens doesn't include area. A lux is one lumen over one meter square. The lumen is a measure of Luminous flux - Wikipedia, the free encyclopedia. "In photometry, luminous flux or luminous power is the measure of the perceived power of light. It differs from radiant flux, the measure of the total power of electromagnetic radiation (including infrared, ultraviolet, and visible light), in that luminous flux is adjusted to reflect the varying sensitivity of the human eye to different wavelengths of light. ... The luminous flux accounts for the sensitivity of the eye by weighting the power at each wavelength with the luminosity function, which represents the eye's response to different wavelengths." From the luminosity function page, "It is based on subjective judgements of which of a pair of different-colored lights is brighter, to describe relative sensitivity to light of different wavelengths. It should not be considered perfectly accurate in every case...There are two luminosity functions in common use. For everyday light levels, the photopic luminosity function best approximates the response of the human eye. For low light levels, the response of the human eye changes, and the scotopic curve applies." The lumens listed on a bulb's package is using the photopic function. Which is fine in areas lit well enough for the eye to use the photopic response. When the area isn't lit well enough for that, the eye will use the mesopic response. Under those conditions, the bulb's lumen value will be off from what people are seeing, since the wavelength weighting used for the lumen measurement is off from the eye's response. Since this discussion started off lower lumen replacement bulbs appearing brighter; Brightness - Wikipedia, the free encyclopedia "Brightness is an attribute of visual perception in which a source appears to be radiating or reflecting light.[1] In other words, brightness is the perception elicited by the luminance of a visual target. This is a subjective attribute/property of an object being observed and one of the color appearance parameters of color appearance models. ... As defined by the US Federal Glossary of Telecommunication Terms (FS-1037C), "brightness" should now be used only for non-quantitative references to physiological sensations and perceptions of light."
See also Costco Online: Feit Electric 4’ LED Shop Light 2-pack and Sam's Club: 4-foot LED Shoplight - Sam's Club
maybe Costco online? EDIT; Oops - just read fuzzy's post right above But yikes! The online price is a lot more then buying at the local store .
Is the local store pricing them as singles? The online item is priced as a 2-pack, and includes shipping.
I'm going to keep those LED strip lights in mind for grow lights for seedlings. That is the likely first need for a strip light I'll have.
Now discounted to $29.99 each, through August 16, at a Costco near me. ------------------------- CORRECTION: $6 off the normal local price, which varies by location. E.g. I discovered this markdown during a supply mission for an upcoming event. That store (not my normal local store) had this item marked down from 35.99 to 29.99. Later, after the event work for the day was complete, I went to my local store with my own card to fetch this for personal use. Here, it was marked down from 34.99 to 28.99. When Hill originally posted this, his store was selling it for about $39. Unless it had another markdown since, his store is likely selling it for a higher price than I am seeing.
Thread reboot, update 1.5 years later. Did I mention I love LEDs? Prices have come down and specs up nicely. Just bought 4 more T8 LED tubes to replace the remaining fluorescent tubes in the garage. The fluorescents hadn't bit the dust yet, but couldn't resist. Again went with Hyperikon based on specs and price: -4 pack at $11.20 a tube, couldn't find better specs for less -18 watt, 4000k (daylight glow), frost cover as the tubes are exposed in the garage -2250 lumens -125 lumens/watt -spent $18.50 each for a couple lower spec Hyperikon LED tubes 1.5 years ago, these are still working great -the new ones are hybrid tubes (works with or without ballast), but ballast bypass is always better as the ballast itself will consume a few additional watts otherwise -I shop at Costco too, but these have better specs and the Costco bulbs don't allow ballast bypass; Home Depot had Philips 4' LED tubes at only $7 each, but again, no ballast bypass and inferior specs
