The coolness or warmth of light is something to consider when planning or replacing your bulbs. A cool light in a room can look crisp if done well, or it can look clinical and cold. I like to use a variety of options for my clients especially in the bathroom, where they may desire a daylight color for makeup application(so that makeup isn't applied too heavily or in strange patches due to poor lighting) and perhaps an evening color for a soak in the tub.
Natural daylight is the usual point of reference, but some daylight can be very cool. The light from a blue or overcast sky, for instance, or from a northerly direction is usually much cooler or bluer than the clearer, purer white sunlight overhead at midday (this is why I like to choose paint and fabric around noon and take the samples outside if possible, since the showroom light can influence my color perception).
You can use a Kelvin chart to assess the degree of warmth or coolness of light. The scale is given in degrees of Kelvin which defines the "color temperature" of a given light from blue through white, yellow, orange and red.
Two of the warmest lights are the flickering of a candle and the kinetic light of a glowing fire.
The luminous intensity of a light source is expressed in candelas (one candela is approximately equal to the luminous intensity of one candlestick); the amount of light energy flowing from that source is expressed in lumens . You can roughly estimate the lumen level of any room by totaling the lumens emitted from all the bulbs illuminating that room. For instance, one candle produces about 12 lumens, an 80 watt fluorescent tube produces about 4,500 lumens (57 lumens per watt). You can usually find these measurements on the packaging.
You can then relate these measurements to your specific needs. As a rough guide, you need a minimum of 2,500 lumens for intricate visual tasks, directed at the work surface. Casual task and general background lighting require about 1,500 to 2,000 lumens, with it arranged comfortably.
An Interior Designer can help with intensity, placement, color and purpose. I have placement tricks I use for seeing oneself in the mirror (to avoid casting unflattering light down), highlighting artwork or sculpture, and much more. Lighting effects mood and creates visual interest too.
I believe many points and options for lighting make a comfortable room. I like to put lights on a dimmer, and have different sources for lighting. Better lighting can really change a room!!