Well I think it\'s a good idea to have some kind of more ambient lighting in the room to cover for the to excessive shadows created by a desktop lamp. As I live in Northern of Sweden I can\'t depend on daylight for that purpose (and it is not a good thing to rely on something that varies so much)
What you should put your focus on when buying a light is how well it renders color, the light temperature, (measured in kelvin) the Watts and finaly the Lumens (measures the intensity of light). Ordinary incandescence lightbulbs does not render colour as good as flourecent lighting, and the bluetinted \"daylight\" bulbs only contains a blue filter that makes the light colder.
So, on the ordinary fluorescent lights (here in Sweden anyway) it is a 3 digit number. Typically 830 or 940 or something similar. The first digit stands for how well it renders colour ie. how full the spectrum of light is. 90 is a very high CRI value (Most full spectrum lights) and that is what the 9 stands for. The other two digits stand for the kelvin temperature. (approx. 3000 or 4000 in these cases)
These are some guides i found to light temperature:
Warm White 3,000K to 3,500K
Cool White 4,100K to 4,200K
Full Spectrum 4,800K to 5,500K
Daylight 6,000K to 7,000K
but I also read that the definition of a full spectrum light is \"any lamp that had a color-rendering index above 90, a correlated color temperature (CCT) between 5500oK and 6800oK, and a spectral power distribution (SPD) for visible and UV light similar to that of open-sky natural daylight\"
The colder light the less lumens you get per watt, so if you invest in a full spectrum light you might need more Watts. In other words your ordinary desktop lamp might not give enough light for your purposes.
Right now I\'m using a 11W 940 ordinary desktoplamp (the highest I got hold of here in Umeå) I\'m not satisfied however and I have written to santa clause for a light armature that is fitted with a 960 fluorescent light. I will use my desktop lamp if necessary as a flexible way of getting light where I want it. I will probably also try to get the surface where I paint a touch lighter to work as a reflector for the light.
I hope I got all the information correct as I wrote most of it from the top of my head.
And remember that Full spectrum light keeps you sharp and focused as well!
