Are they A Good Thing for cheering up a kitchen through the winter, and possibly having a beneficial effect on the symptoms of SAD? I'm having some bother finding a 6' one locally but if they're worth having I'll continue the search.
Si
And... is there any difference between 'normal' daylight tubes and 'full spectrum' jobs?
Definitely not. They have the most appalling effect on the colour of food, and unless you lined the ceiling with loads of tubes to get the lighting level up to that of midday sun, the colour will look wrong.
SAD needs a bright light. There's no evidence colour makes a scrap of difference, but the manufacturers of special lights like you to think it does so you'll buy their very expensive replacement tubes.
One 6' tube mounted on the ceiling probably isn't anywhere near enough to make any difference. If you want to make a SAD lamp, the cheapest way is probably to buy a 4-tube modular ceiling luminare designed to sit on a 600mm ceiling tile frame (either 600mm square or 600x1200mm). They're dirt cheap from an electrical wholesaler and often free from a skip. You can hang it on the wall like a picture next to where you sit/work, like a sort of fake window.
Thanks Andrew, and Adam, for the advice. It was just a thought.
Si
Probably BS though as sunlight is not blue and its lack of sunlight that causes SAD. I would use warm white tubes myself and you need plenty of them, one tube is not what you usually see to treat SAD, maybe five tubes or a 250w metal halide lamp?
writes:
You need to tell Screwfix that as their spectral diagram in the Lamps section shows SAD application as being beyond Daylight (16000k). Snakeoil perhaps!!
Rob
Cant place the link offhand but it was serious research, blue LED because its a very efficient generator of blue light aginst tungsten or even fluro. Sunlight contains a lot of both visible and increasing amounts invisible blue>violet radiation....
Intensity dosen`t seem to be universally accepted as the main factor ,though personally think it is probably one factor.
Adam
I used to know someone who had a 250W tungsten lamp in a white painted bog not much bigger than a shoe box. Certainly woke me up!
I find that sufficient wake up brightness can be obtained with halogen downlighters in a white painted bath/shower room. Add the reviving influence of splashing water to the brilliance of the lamps and you should come out feeling a whole lot better. [One proviso is to make sure the transformers on the downlighters are able to take any wattage that is likely to be plugged into them. The ones that were fitted in our kitchen were only meant for 20W lamps, something that the fitter failed to mention, resulting in some interesting on and off cycling of the lamps as they were gradually replaced with 30W ones without realising.]
S
I am trialling a CFL daylight bulb in the bathroom, a bedroom and dining room at the moment. They are all nice and bright - 150w equivalent.
In the dining room, the light is OK in the day as it gives a bit of a boost to daylight which is coming through the patio doors. But at night it looks plain odd. Its too white, looks cold, and visually is less preferable to the warmer CFLs in an adjacent room or the tungsten spots in the kitchen. It does not promote a feeling of well-being at night- just a feeling of unnaturalness.
In the bedroom, again it looks unnatural, but is a better light for getting dressed and for mrs dg putting the make-up on. Its a shock when the light is put on on during the night after darkness or if waking up when its dark. It's not as calming as some warm low wattage CFLs which we have in bedside lamps.
Its not a nice light to wake up.
In the bathroom, its a nice useful light. So this one will probably stay and the others will be removed.
Full spectrum bulbs are just too subjective - as are all colour temperatures really.
What exactly is colour accuracy and how is it needed at home? Its a bit irrelevant
If you are doing photography, or need accurate colour rendition for some commercial application, then fine, but at home, at night IMO, a warm yellow is the most "natural"
dg
Sorry - I feel that the 2700K CFLs are truly ghastly for use in the living room in the evening! Even standard tungstens are a bit too yellow. Not certain what temperature ours are, 4000K I think, and they are fine.
Certainly anyone looking from outside might think it cold, but we are quite happy. And warm. :-)
In line with the other thread, we have in our kitchen some of the 3500K triphosphor under-cupboard low profile lights (from TLC). The colour really is very acceptable. The use of multiple sources (rather than a single 6 footer) reduces the shodow-casting.
If they could be used, I'd expect you to find them OK.
(PS SAD has all sorts of interesting connections with the thyroid. But I'd better stop there. :-) )
I'm all ears. Email works if you faff with it.
Si
Yep, these are very good, and I even keep a 20W one as a handy portable light. Only problems I've had is with the ballast failing and then when you try to link in a replacement you find they change the end connectors every year so you always have to cut them off and use an ordinary connector block. Grrr. Still, the spare ends come in handy when you want a longer flex for your old fm radio - or one in every room...
S
Nothing less than 3500k suits me. I used to like the old gas lights, a greenish tinge in preference to the yellow electric lights. I wonder how they were in the colour temperature/rendering stakes?
Yes.
As I said in another thread, daylight is actually quite complex. Although it measures 5400K, because the red and blue components are split up in the atmosphere (red mainly coming direct from the sun, and blue scattered and coming from all over the sky), a few clouds can radically change it. A cloud blocking direct sunlight can push the colour temperature very high (probably close to your 16000k). When you look at objects illuminated by daylight, you'll see a very different colour temperature depending if the object is in direct sunlight (with red components) or in shadow (so only blue components). For anything other than a horizontal surface under a clear sky, an object illuminated by sunlight will never actually see the 5400K -- it will either be higher or lower depending on precise circumstances.
I have a 20,000K metal halide lamp. It's fun for lighting up the garden at night at Christmas if it's covered in snow, but quite useless for anything else (except possibly lighting corals and tropical fish which is what it's designed for). However, you can't run it indoors for longer than a few minutes, as although it has an outer glass bulb and an explosion-proof luminare (as required by all MH lamps), it still generates too much ozone (too much UV leaks through the outer glass bulb, although not out of the luminare). Incidently, This colour temperature, lacking severely in reds, makes people's skintone look very sick ;-)
Right. It's intensity x time = Dose Timing or when the light is provided counts as well. Morning light is best. The spectral sensitivity curve peaks in the blue, but it's a broad curve like the other human spectral sensitivity curves, so any broad band white light will do. A 15-20 minute walk outdoors even on a bright cloudy day will do it as will gazing out a daylighted window for a similar time. It takes a substantial amount of electric lighting to equal that dose level. Spectrum counts for very little. Several articles and technical papers at:
It appears to me that exposure time and time-of-day and brightness matter more than anything. I have heard of beneficiel effect of certain colors (more blue or more green), and hypothesis of a "cirtopic sensor" with a spectral response peaking in the greenish blue. Google on "cirtopic response" brings up 4 links (23 without omitting very similar results), mentioning peak wavelength anywhere from 465 to 490 nm. With the small number of hits, I give fair chance that cirtopic response may not be for real.
If cirtopic response does exist, ordinary halophosphor high color temp. fluorescents such as "daylight" probably hits that better than any other white light source - though high color temp. triphosphor has a minor but slightly narrow band that *may* hit the cirtopic peak square-on. I have no idea if cirtopic response is narrowband, or maybe as wideband as scotopic response (in which case having high CCT, high s/p ratio and high luminous output probably help more than any spectral details).
My experience is that 6500K fluorescents appear stark and often create a "dreary" atmosphere unless illumination level gets to some extreme that is typical of daylight, or at least a brighter degree of overcast - something like 15,000-20,000 lux.
Personally, I like triphosphor fluorescents with CRI in the low-mid
80's. The color distortions are not in the direction of making colors darker or duller, while non-triphosphor fluorescents do tend to make colors (especially reds) darker and duller. I think it helps to have colors brighter and more vivid for lighting to have beneficial mental effect. Having "full spectrum"/"broad spectrum" fluorescents with CRI around 90 or in the low 90's instead of 80's-CRI triphosphor goes back to darkening and dulling colored objects although only slightly, and also has significantly lower light output.- Don Klipstein ( snipped-for-privacy@misty.com)
Was it from Flinders University. I remember seeing a story about the blue LED glasses awhile ago on TV. Found this link:
___ Circadian rhythm phase shifting with the use of small light sources Bright light stimulation has the capacity to shift the timing of circadian (24-hour) rhythms of humans (the body clock). Sunlight or specially constructed bright light boxes generating up to 3,000 lux of light at the eyes can shift the timing of circadian rhythms to a later or earlier time dependent on the timing of the light exposure. This phenomenon can be used therapeutically to treat certain types of insomnia, jet lag, shift work fatigue, and winter depression. However, these light sources are often not available and have disadvantages of non portability and inconvenience which reduce patient compliance and therapeutic effect. To overcome these disadvantages we have developed small light emitting diodes (Leds) as an effective light source. Although their total light output is minuscule compared to the sun or light boxes, placed close to the eyes they can provide up to 3,000 lux of light intensity. The first studies have found significant melatonin suppression and phase delay during and following LED light stimulation respectively but only with certain LED colours. The studies have found the most effective LED colours to use for circadian rhythm re-timing are in the blue and blue/green end of the coloured spectrum. This research has led to the commercial development of blue LED glasses for the application of bright light therapy, for sleep difficulties caused by these body clock disorders. Funding support:
Flinders Technologies, 1999-2000.
Principle Investigators:
Leon C. Lack, Prof., Helen R. Wright, PhD.
Publications:
Lack, L., Wright, H., Gibbon, S., Kemp, K. (2005). The treatment of early-morning awakening insomnia with two evenings of bright light. Sleep
28, 616-623.Wright, H., Lack, L. C., Tennaway, D. F. (2004). Differential effects of light wavelength in phase advanging the melatonin rhythm. I Pineal Res., 36,
140-144.Wright, H.R. , Lack, L.C., and Partridge, K.J. (2001). Light emitting diodes can be used to phase delay the melatonin rhythm. Journal of Pineal Research,
31(4):350-355.Wright, H.R. and Lack, L.C. (2001). Effect of light wavelength on suppression and phase delay of the melatonin rhythm. Chronobiology International, 18(5): 801-808.
Wright, H. R., Lack, L. C., Kenneway, D. J. (2004). Differential effects of light wavelength in phase advancing the melatonin rhythm. J Pineal Rec, 36,
140-144.___
Liron
"Adam Aglionby" wrote in message news: snipped-for-privacy@d45g2000hsc.googlegroups.com...
Soft start as well. It wasn't until the end of the 60s that the station I most used converted to fluorescent. (That, IIRC, means that they had beeen converted to natural gas a few years earlier.) The change in colour was horrible - from quite OK to ghastly.
I'd guess that CRI depended on the materials of the mantle (thorium and cerium oxides?) and its age.
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