No matter the season, indoor window light is stunning when you know how to use it, even if you're using your phone camera! That's what I want to fill you in on now.
Strong indirect light is what you're looking for. On overcast days you can use any window (a door works too!) Putting your subject in a spot where they face the window is the easiest thing to do. If you want to experiment, put your subject on a 45 degree angle line, from the window- that's how you can produce the shadow on one side of a face. Sometimes too much info is just too much… but please let me know if you have questions or want me to share more!
