colour temperature of bulbs - Page 1
Forum section: electronics / general

author: Simon
author_rank: Unknown
timestamp: November 06, 2009, 08:54:20 pm
content: After a heated discussion on another electronics forum about energy conservation and the inevitable point being made of how crap modern energy saver bulbs are I started to validate my theory.I remeber when these infamous eco bulbs came out, they cost a lot of money and it was a hard job getting people to see the maths of how they would pay for themselves. my dad worked for a marketing company called amway and they were selling these so we bought a couple. I remember that they did exactly what it said on the box: a 20 W bulb made the same amount of light as the previous 100 W bulb. being interested in electronics etc I read the box all over and noticed the unexplained 6500 K. I never did know what this meant until many years later by which time i had forgotten the affair with the lightbulb.Now roll on a few years and hec the worlds falling apart: we are bing banned of the simple liberty of choosing our own bulbs and are being made to use eco bulbs. As I lisetn to the wails and whines about how unreliable they are and how crap the yellow lihgt that they make looks I think: hang on a minute ! it was never like this.Fortunately by this time I've been into photogfraphy for a few years and know very well about colour temperature now and that 6500 is daylight/flashlight. The wheels in my head start to turn as i grab boxes of eco bulbs and study them. low and behold i find the proof I was looking for: humanity has been betrayed and tricked again, the very good quality eco bulbs are now a matter of the past, we no longer need to be convinced to use them we have to in some places by law. and of course the manufacturers are now laughing as they mass manufacture cheaper(?) 2700 K bulbs aka yellow naughtily called warm white. long gone are the true bulbs that actually make 6500 K of light which is what we huimans need to see by.Is there anyone else that has found this ? Luckily i have found "daylight" aka 6500 K eco bulbs on ebay and am gradually changing all bulbs in my house. I am pleased to report that I am sitting in "daylight" and not feeling drows as i used to under yellow light (yes it has an effect on some people) I've also found that 4200 K bulbs are also almost as good as 6500 infact I can hardly tell the difference. it also goes without saing that 6500 K light makes morer light per w of power simply because we are more sensitive to this light, it is after all the light we have evolved under for thousands of years

author: Unknown
author_rank: Unknown
timestamp: November 06, 2009, 09:58:07 pm
content: Interesting co-inkidink!!! I just spent $300 buying lighting fixtures for my workbench, in attempting to find the most workable setup. I found similar issues with the yellow-cast light being a problem in working with small electronics components. It became very apparent to me, very quickly that ALL of the CFL lamps that I bought over the last two years were warmer on the color temperature scale and put a strain on my eyes-- I had to resort to using "cooler" halogen lamps, to get the clarity that I needed. But "cooler," of course only represents the more human definition of color warmth. On the Kelvin-based scale the higher the real number, the physically hotter, and more blue-white the light. In fact the halogens where much hotter in practice-- I actually singed my hair on the fixture twice (yes, I know, I probably shouldn't reproduce.) So I went out on a trek for a better light.... I found the following-- 1.) At least in the U.S., no one bothers selling high-end light fixtures anymore-- it's virtually all cheap Chinese crap. 2.) Halogens are increasingly harder to come by in the higher wattages (due to the fire risk.) 3.) There are scams everywhere, even in the consumer lighting market!There was hope-- I found a newer manufacturer of lighting fixtures called "Ottlight." They offered moderately priced stuff in the $30-$250 range, and they only sold their stuff in large-chain craft stores, like the ones that sell sewing/knitting/fake plants and stuff. So I bought three in the range-- their highest end, one in the middle, and one at the lowest end of the price scale. Their claim to fame was the "full spectrum" light output, specifically suited for "crafting." Great! Unfortunately, when I brought it home I found that the design and build quality of the highest end-unit and the lowest end unit was unbearably bad-- the light would not stay aimed in where I would put it, or sag over time. But the biggest problem-- on the high end one-- it actually put out a shit-load of RFI-- my Rigol would see a continuous 1 Khz, 1mv shark-tooth signal, with the probe just sitting on the bench! Shorting the probe out would kill the signal-- it wasn't noise on the ground. So I returned the top and bottom end-unit, but kept the one with the magnifying lens built in-- I actually really like that one. But in general, Ottlight is a scam-- they add a 100% markup, and then have their retailers put it on sale every other month at what should be retail pricing. And IMHO, of all their dozens of models, only the "Jupiter" model with the magnifying lens is worth a damn.So I went back to the halogens two weeks ago. I then found a new type of CFL for sale at the hardware store-- the package said "Full Spectrum, for CRAFTING" (from a company called TCP) and had to try it. It was 50% more expensive than a standard "daylight" CFL, but still only $10 U.S. for two. I also saw those cheap swing-arm lamps from my youth on sale for $15.99 U.S. so I bought one. And YES-- this turned out to be the ideal solution! The whitest light available, exactly where I needed it, and it only cost about $26.00 U.S. with a spare bulb! I went back and bought another lamp, but they were all out of the bulbs-- apparently they are VERY popular-- and I can see why.See above where I said "virtually all cheap chinese crap?" My new swing arm lamps are made in China, and they're actually BETTER than the vintage 1970 one my dad had-- and it that one was my favorite lamp of all time. Just be cautious of the wide range of quality that you see out of China.As for buying lamps off of eBay-- I would recommend against it-- everybody and their brother says that their CFL's are now "cooler temperature,' 'scientifically designed for 7 x 10^3 - 5/9 +40 degK, etc." but if you go to a reputable store, any buy the most expensive one there that says "True Color/full spectrum for Crafting" you should be okay-- if not, simply return it!As a side note-- I also tried the ultra expensive high-powerered LED lights-- $35 U.S. for just the bulb-- the light is actually too cool (high on the K scale) and is incredibly harsh-- polar opposite extreme of the yellow incandescents /CFL's.Yet another side note-- I got the 100W CFL for my lamp-- even though it's only rated for "60 WATT BULB" the actual power dissipation of a "100W" light output CFL is 23W. It takes about 1 minute to warm-up and produce a good amount of light, but I think you'll be impressed. And, no more singed hair!-Trent

author: Simon
author_rank: Unknown
timestamp: November 06, 2009, 10:32:00 pm
content: hello trent, yes i was dubious too of the ebay lights, infact still wonder if my "daylight" lamps are 6500 K as it says daylihgt on the box but not 6500 K, still its better than 2700 K and at worse is 4200 which is not too bad.led lights are a bit of a problem, I tried to take a photo at work under the light of a led torch and my DSLR just ignored the light, quite normal i suppose as camera sensors see infrared mostly.

author: Zero999
author_rank: Super Contributor
timestamp: November 13, 2009, 06:46:20 pm
content: In my experience, eco bulbs never live up to their expectations.A 20W CFL is supposed to be equivalent to an 100W but in my experience it seems to be more like 80W.The colour rendering is also much poorer and it does take longer for them to warm up, even those with modern ballasts.Low power factor and harmonics can also cause problems.They're not comparable with dimmer switches unless you buy the really expensive dimmable variety.I still think they're a good thing as long as one is aware of their limitations.I don't think the government should ban incandescent lamps but perhaps putting a high tax on them would be a better idea.

author: Simon
author_rank: Unknown
timestamp: November 13, 2009, 06:51:49 pm
content: hey Hero999 welcome.Like i said i am now using 6500 K bulbs and they are better than tha crap from the shops at 2700 K. I agree they don't quite live up to expectations but is a 20 W bulb still gives 80 W of light thats still fine by me

author: Zero999
author_rank: Super Contributor
timestamp: November 13, 2009, 10:45:59 pm
content: I don't like daylight simulation lamps because they never simulate sunlight, they produce is a dim greyish blue light similar to a cloudy day.

author: Unknown
author_rank: Unknown
timestamp: November 14, 2009, 02:09:33 am
content: Agreed. The newest generation of "Crafting" lamps seem to address this problem. They are very well-balanced, indeed.

author: Simon
author_rank: Unknown
timestamp: November 14, 2009, 08:04:22 am
content: well the 2700 K lights make me sleepy, if the light is a bit lacking from a 6500 K lamp using one thats more powerful helps, as I wanted a couple and to put one in the lounge I bought a pair of 20 W, I am using one in my tiny room, really its well overpowered but its a nice light and looks much better thasn the one in the louge which could do with being 25-30 W,15 W is probably ok for my room when i get one

author: Unknown
author_rank: Unknown
timestamp: November 14, 2009, 09:06:46 am
content: I have nice CFL globe here, it is 200W (yes two hundred), it is about 100mm diameter and about 350mm long, is the equivalent of a 1000W halogen (it is also 6500K), it lights up the back yard a treat at nightOnly problem is the tubes seem to be thinner walled glass than normal globesI have already cracked one globe)I will pull one of them appart next week and photograph the insides, they have a cheap SMPS in them and it is not well designed, one blew up the other day (a small CFL just makes a fut, this one made a huge explosion and a lot of smoke (so much so it set the fire alarm offWhich is VERY VERY LOUD ( all my smoke detectors feed into the house burgular alarm and then to a monitoring station, so here I am trying to punch my code in t stop the sounders, answer the mobile (was the monitoring company asking if I needed the fire brigade), while trying not to trip over the pile of SLA's by the door and trying to cut power to the globe before it burnt the cave down

author: qno
author_rank: Frequent Contributor
timestamp: November 14, 2009, 08:35:10 pm
content: Anyone tried the LED version already?Here in Europe we now have a third option Light bulbs wit LED technology.So far the only white LED is have seen and used are either a combination of Red Green and Blue or a Blue LED with a phoshor coating.Both lacking the rest of the color spectrum the incandescent does radiate. From IR to UV.These LED bulbs are for instance not suitable for growing plants under. But are they OK for humans in the long run?

author: Simon
author_rank: Unknown
timestamp: November 15, 2009, 08:14:38 pm
content: the overly bluish light is not always comfortable, I would think the multicoloured lights are more pleasant, we shall see when the price drops

author: Unknown
author_rank: Unknown
timestamp: November 16, 2009, 03:01:40 am
content: I recently purchased a 7w (single) LED lamp as a trial, and found the light way too harsh for hobby use-- there is a very blue-white spot surrounded by a 'whiter' ring-- and the transition is very sharp. I think LED lamps make perfect sense for flashlights (torches,) where you would want a high intensity spotlight, but every-day purposes, I definitely prefer the more diffuse light from my full-spectrum CFL's.I use my LED lamp as a night-light-- I use it to light my living room to keep the monsters away.-Trent

author: Simon
author_rank: Unknown
timestamp: November 16, 2009, 07:43:39 am
content: we have led torches on the portable phones at work, they are awful when trying to take a photograph thats how non standard light they are. the camera completely ignors the ligtt from these torches, whereas my ordinary torch is fine for adding a bit of light to photographs (usually the insides of a radiator)

author: Zero999
author_rank: Super Contributor
timestamp: November 16, 2009, 11:24:47 am
content: I wouldn't even use white LEDs as a night lamp because they produce too much blue light.The problem with blue light it it destroys your night vision: If you need a night light, then I'd recommend a longer wavelength yellow, orange, red etc. Blue light does have the advantage of being more efficient at low light levels: the dark adapted eye is more sensitive to blue light but that's what creates the problem.

author: qno
author_rank: Frequent Contributor
timestamp: November 18, 2009, 04:25:39 pm
content: I once used an USB microscope that was equipped with extra white LED's to inspect and photograph PCB's.The PCB's where the green epoxy type but the camera made it look a completely different color due to the LED's.The burned traces where also difficult to distinguish.

author: Simon
author_rank: Unknown
timestamp: November 18, 2009, 05:13:52 pm
content: camera sensors are most sensitive to infrared light, in fact all camera have an infra red sensor in front of the sensor to try and make the recording carachteristics more like the human eye, like I said when I tried to use the led lights in the phone at work the camera just did not see it