Light is measured in kelvins from a cameras perspective (5600k) - this translates to temperature and effects the cameras white balance which must be set correctly to avoid an overly blue or orange image.

The temperature of your lighting may be different and depending on the time of day, the sun or outside light may also be different therefore it is good practice to know these kelvins to set your wb (white balance) accordingly.

So how do you set white balance?

So regardless to indoors or outdoors, you should use some white material (officially 70% Grey), In industry, this is a specific piece of equipment, as even white can be produced slightly off balance a white piece or paper, a wall, even a shirt or curtain could be used if they are white. Aim your camera at this material and press the wb button or setting in the menu system, this should then calibrate your camera to the correct temperature of the location.

This should be done at all new locations or hourly if the time of day is altering.

Lighting Continued:

After watching the rule of thumb for 3 point lighting above, it is good to know that these rules can be broken, and often are to get more interesting set ups for interviews, fictional scenes and b roll sequences.

Some techniques to try different lighting scenarios with 3 or less lights can be found in this video - watch this video for more theory lighting such as my favourite 'Rembrandt lighting'