I have always been fascinated by the light streaking in from a window. For photographic purposes, such ambient light creates expressive effect on portraits where you can harness the light either as a key light or fill light. Shooting in ambient light would, however, give you shadows in unwanted places. Shadows can either make or unmake your photo depending on their placement or location where you let them appear. Perhaps, the most appropriate time to shoot using window light as your light source is when the sun is at its peak of strength.
Although I havent tried it yet but worth experimenting would be to block or temper down the strong light with a diffuser to soften it like a modelling light. The first two photos were taken in mid daylight and the venetian blinds separating the subject from the light source acted as diffusers to tame down the strong mid-day sunlight. Using reflectors would also help disseminate some light to recover details from the shadows. The third photo was taken late in the afternoon and it is during this time of the day when an artificial light source should be considered and mounted to provide additional illumination.
When shooting in ambient light like this, it is always a good practice to mount your camera on a tripod, use a small aperture and longer shutter speed and tell your model to stand or hold still for at least 2-3 seconds. This way, you can let in more light into your sensor using a lower ISO. Meter your subject using spot metering or if you have a light meter, you can choose to meter your settings by placing your light meter on the particular area where you want more light to appear.
Lately, i tried combining window light with artificial light from a speed light to get a more predictable result. In photography, you cannot always capture what your eyes can see. You should introduce additional light somewhere to eliminate or create shadows. The last sample photo was also taken in mid-daylight but the window light was diffused by the curtains, hence, i tried introducing artificial light from my speedlight mounted on a diffuser umbrella and placed at the back of the model to eliminate the shadows. The result is a more natural looking photo just like what my eyes have seen from the location where I took the photo.
Modelling credits from top to bottom: Gabrielle, Nicole, Camille and Elaine
Lenses Used: first two photos - Nikkor 85mm f/1.4D IF, third photo - Nikkor 50mm f/1.4D AF and fourth photo - Nikkor 16-85mm f/3.5-5.6G ED AF-S DX VR