Dryness most likely. You're right -- not enough tears can cause your eyes to be light sensitive and water. The issue is that when the baseline tear film is insufficient or of poor quality (e.g. Breaks up quickly rather than maintaining a lubricated surface), then the eye is sensitive and responds to minor irritation like sun, wind, dust etc. By flooding down tears.
Light sensitivity. Usually the casue is dry eyes or allergies. It's best to d/w ophthalomolgist who can do a shirmer test to assess tear production as well as examine your eyes to assess for and allergies or infection.