A question on Ethnography

I posted this on the module forum but I thought I'll post it here as well since I have kind of neglected this blog after all the festivities and celebrations. And considering that this blog will be graded as my participation, I ought to do something soon! I promise. =)

I am just wondering that it is a necessary criterion for ethnographers to observe without imposing a presence.

For example, if I'm observing the happenings in a lecture theatre during lecture and I go in with a bulky camcorder or worst still a film crew, wouldn't it be counter-productive in that I've actually created an artificial presence that will not be there under normal circumstances? And in this case, the people being observed may become aware of them being watched and hence, behave in a different (possibly more composed) manner. This will mean that the observations are not attuned to the reality, but rather a forced reality. I'm sure those of us who have went through education in Singapore long enough will know that teachers do behave differently and that they may even request the students to behave in a certain manner when an examiner from the Ministry of Education is scheduled to sit in during class.

But on the other hand, such artificial presence may actually yield unexpected discovery. I remember my Sociology lecturer sharing his experience of doing an ethnography study on resurgent Christianity in Singapore (Goh, 1999). While he was observing a baptism, his presence actually affected a new believer in that the believer was unable to verbalize tongue despite encouragement (socialization) by fellow members. It was only when he (my lecturer) was ushered away, and after repeated socialization that the new member was able to speak in tongue.

Hence, the observation on the effects of his presence (and many other factors of course) actually made him conclude that Charismatic Christianity may not be as rational as people believe it to be.

With these conflicting examples, I am interested to know whether or not ethnographers should observe without people knowing or vice versa. Any ideas?

Reference:
Goh, D. P. S. (1999). Rethinking resurgent Christianity in Singapore. Southeast Asian Journal of Social Science, 27(1), 89-112.