In Lighting Options we touched briefly on the benefits of using window light as your primary light source for boudoir photographic lighting. Here I would like to look at this in more detail.
First off I should point out that 'window light' is too too much of a generalisation; there are so many factors which affect it:
Size of window
Which direction it faces
Time of day
Time of year
When you are looking for a suitable window, there is no substitute for a bit of advanced planning: take your camera around the house and take some snaps. I tend to take a tripod and use the camera's timer so that I can be in the shot to study the way the light looks on a skin (it can be a time consuming process and I've run out of volunteers). Pay attention to the following:
How much space do you have in the room? If it is too small you will end up using a wide angle lens and run the risk of foreshortening. See here for more on that.
How big is the window? Small windows are ok for head and shoulder portraits, but you need something bigger for full figure work.
Is there enough light? What shutter speed are you able to use at ISO 400 or below, and how does that vary throughout the day? If your shutter speed is too slow you will need to either use a tripod or increase the ISO - which can introduce a grainy feel to the shots.
What colour is the light? Window light is much less controlable than flash. Its colour will change through the day (which you can often use to your advantage). More problematic can colour cast back from the rooms walls etc. If you have non-neutral colours on the walls/floors, study your test shots very carefully to see if those colours are affecting your results.
In this example there are a couple of things to note:
The room isn't very big; the distance between me and the model is really too small and there is some foreshortening in the shots.
There is a 'sweet spot' of light in the middle of the room.
The tone in the room is very neutral - all greys and whites which means that there are no colour casts to worry about.
This shot was taken at the start of June in the south of France. I went to use the same room in December and there was nowhere near enough light.
ISO 100 1/200 sec f2.8
Having found a suitable window you need to plan how you are going to use it:
Glamourous effect: you should aim to be between the window and the model. This can be awkward sometimes - you may end up crouching down so that you don't block out the light!
Getting artistic: side lighting and back lighting can produce excellent results. You will need to consider the balance between light and shadow though. If there is too much contrast between the light from the window and the shadow side of the model you may need to use a reflector to bounce light back into that part of the scene. Fill flash can also be used if you are back lighting the model.