That makes sense Arfa. I guess you just saved me trying to find my croc clip probes or risking blue lights!
In summary then, CFLs almost certainly save more energy than tungsten lamps when dimmed. It's best to buy all lamps from the same batch when dimming more than one to ensure they glow the same. Until they devise low power dimmers you must have more than one lamp or you won't load a dimmer properly.
Thanks to all for comments.
Peter Scott
The colour shift as something cools and dims seems to be programmed into our brains as expected behaviour. (That effect has a name which I can't remember, i.e. the way you expect higher lighting levels to have higher colour temperature).
With fluorescent tubes, the colour changes in less predictable ways. With some I have, they tend to go purple (probably a loss of green components), and I strongly suspect the CRI drops considerably, although I have no way to measure that. The drop in CRI and change of colour probably make any change in colour temperature meaningless, although very likely.
We use dimmable fluorescents for TV lighting - and I've not noticed the LD having to compensate noticeably when dimming them. As he certainly would have to do with tungsten. To the point where they wouldn't normally dim tungsten but use ND filters.
My guess is you are using something special and expensive, possibly even something specially designed for dimming, and not bog standard colour 830 or similar. There are fluorescent lamp controllers which drive multiple tubes of different colour [temperatures] to create variable colour temperature output.
I've not tried dimmable CFLs using a normal dimmer, but have Osram dimming ballasts in the kitchen - and those really don't change colour noticeably. The other lights are tungsten so give quite a good comparison if dimmed together.
Well if the lights were dimmed substantially I guess you wouldn't know how brave a face he was putting on :)
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