In ,
Adam Aglionby wrote:

On 1 Oct, 10:07, "Mungo \"Two Sheds\" Toadfoot"
wrote:
Mungo "Two Sheds" Toadfoot wrote:

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?

added sci.engr.lighting as crosspost from uk.d.i.y

Probably several multiples of price.....

Full Spectrum is marketing mumbo, fluro by the very way it works has a
peak and trough spectral power distribution.
People like the dodgy Dr Ott sell all sorts of impressively packaged
"full spectrum" fluorescent lamps, if you really want full spectrum,
halogen has a continuous spectral output.

Daylight tubes are often just high colour temperature, which in an
internal kitchen might look very cold and as Andrew said can have poor
actual colour rendering. High colour rendering index lamp is really
more what you want, decent lamps made by big manufacturers aimed at
things like the print, textile and car refinishing business be more
appropriate.

Some research says colour does make a difference, been some research
on use of blue LED in resetting circadian rythmns in the elderley,
some research says intensity matters some that time and length of
exposure is most important, doesn`t seem to be a well understood
phenomenon.Offering opportunity for snake oil salesman to enter the
fray.

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 )