This is absolute rubbish. Ever tried using a camera inside with incandescent lighting, then taking it outside without altering the white balance? Incandescent bulbs emit very little at the blue end of the spectrum. However all fluorescent lamps CAN be made to closely emulate daylight. Some tubes are made to give a full spectrum, including UV, more expensive, but commonly used in vivariums.
But it's entirely possible for the brightness to have some 100 Hz modulation present, due to (rectified) mains ripple on the DC supply to the HF ballast. I guess the designers keep the reservoir capacitor value to an absolute minimum to save cost.
I have seen a stroboscopic gramophone speed indicator working by the light of a single HF-ballasted CFL.
On 04 Jan 2008 09:51:16 GMT someone who may be snipped-for-privacy@cucumber.demon.co.uk (Andrew Gabriel) wrote this:-
"Woland" didn't say where this has been recommended, so it is difficult to be that certain. However, given that where this was "recommended" has not been stated I would take the claim with a large pinch of salt.
Yes you are right. It probably has been recommended somewhere, but not by a reputable knowlegable source. Similarly to the news article which started this thread.
I've /never/ liked the colour of incandescent lamps, far too red. I much preferred the incandescent gas lamps they deposed.
One problem with CFLs is that they are marketed mainly in a colour temp mimicking that of incandescent bulbs (warm white, 2700K). If they were much more widely available in white (3500k) with the option of daylight(6000k?) they would be much pleasanter.
There can be some remnant of 100Hz flicker, the smoothing capacitors are often pared down in size from that required to totally eliminate flicker. This may cause some of the critisism of some cheaper brands.
There might be some, but when I've tried varying the DC supply voltage from 200-360V, there's not normally any change in light output as the circuits provide constant current to the tubes. (Going below 200V caused some nasty effects with some lamps, including getting very much brighter in one case, but often dropping back into starting mode.)
As a mechanism for headaches and mood changes, it's 50Hz flicker which is the main issue. That comes from line-frequency operated fluorescent tubes in a few situations... o A cheap tube with badly matched filaments which is conducting better in one direction than the other; o A cheap tube with excessive 50Hz flicker from one or both tube ends; o A tube in the last couple of hours of life where the emissive coating is almost gone at one end, again causing conduction better in one direction than the other. None of these effects are possible with HF control gear.
The capacitor can fail as it's operated above its temperature range, but this doesn't normally happen in retrofit compact fluorescents, as it will still outlast the tube. It can happen in separately ballasted lamps where the ballast is used over many tube changes, although remote ballasts don't run as hot.
You can do that with a 40W mains filament lamp too.
In article , Brian writes
Are some makes of low energy bulbs going to be better than others then for emulating daylight or even being more comfortable to work under?
I print and I know that it all depends on under what light the customer chooses his colour. It can look completely different in daylight/office light etc.!
Just like any modern health scare the report is peppered with words like "could" and "may" and is not worth being given the time of day. Just someone banging a drum.
MBQ
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