Fluorescent dawn
This weekend there was small expo at the local mall and one of the area power companies had a booth promoting compact fluorescent lights (CFL) and LED lighting. There was demonstration to show the difference in power between fluorescent and incandescent lighting using a very large "compact" (if it could still be called such) fluorescent light with an equivalent output of 500W. It took about 90 Watts to run, but that was still less that the regular 100 W bulb used in the comparison.
While the different lamp styles were interesting, what I noticed was a confirmation of what I've suspected since we switched to CFLs at home. Some lights are on as soon as the switch is flipped. Some lights have a short delay before they turn on. Some lights seem to be at full or near full brightness immediately. Some lights start out noticeably dim and slowly come up to full brightness. At first this was a bit puzzling. It wasn't a matter of age, as a couple of the older CFLs in house were the ones switching on instantly to full (or near full, it's hard to tell) brightness.
The answer is wattage. I'll use the equivalent, rather than actual, power here. The big 500W light at the demo was cold before I switched it on. It switched on instantly and was as far as I could tell at full brightness right away. The 100 W CFL was about the same. The 75 W CFLs at home seem to be fairly quick. The 60 W CFLs start out noticeably dim and take time to brighten. The 40 W equivalent globes around the bathroom mirror start out instantly, but take a minute or two to come up to full brightness.
I suspect that besides the power used, some lights might be of better quality and come on instantly. The dim start seems to be related only to power. I am curious about a 25 W or 15 W equivalent would behave, but I have no reason to get such a thing.
I've already gotten used to the slight delay in starting. The slow brightening, like an accelerated a miniature sunrise, I find I rather like, at least at times. I'm really glad I don't get hit with the full brightness of the bathroom mirror lights right away, for example.