I was at Ikea yesterday & it seems that suddenly all their bulbs have halogen middles (not tungsten, not low-energy) and give output in lumens instead of watts, which flummoxed me so much I didn't dare buy any.
From googling today I have found that 1 watt = approx 13 lumens in terms of light output, so if you wanted a 100w bulb equivalent for brightness you'd be looking at about 1300 lumens, 60w/780, 40w/520.
BUT supposing it's for eg a lampshade with a max wattage of 40 or 60 - how do you know how much heat 500 or 800 lumens are giving out??? The Ikea bulb boxes don't say.
