Hi Bernardsia… I think that when the qi of a person has been negative for a while…I mean not just a few days…but more…it becomes blocked on that area, so what Ãve seen in my practice (im a clinical psychologist) is that the area where it has been blocked tends to become not only pale, but also with problems of the skin… spoted skin, rash, soreness, almost anything… and that definitly appears in pictures… But it has to be blocked for a while to cause that..
If its just negative qi, that hasn´t been blocked or stagnant it would be more difficult to see in a picture, because of the picture´s quality, lighting, the type of lens of the camera…it would be more difficult to observe. I think that with pictures you can observe parts of the situation of that person, like for instance you can see the Nose, the eyes..sometimes the ears… but it´s not as acurate as you would like or want it to be.
Hope I helped you a bit… 🙂