[Metric]

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Metric, could you clarify what you mean by "being entangled with the state of the photon."

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The photon P is in an entangled state with some system A if the state of the combined system PA cannot be factored into a state of the form |Psi_P> (x) |Psi_A>. Most states of composite systems are entangled.

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Are you saying that we only get the "weird" results when observing to such a degree that we can determine what slit(s) was entered by the photon?

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You don't necessarily have to perform the measurement yourself -- if the photon becomes entangled with anything that potentially holds information about "which slit," the interference pattern will vanish.

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That would imply that watching the experiment, or pointing a normal camera at it would have no effect on it, but using some kind of super camera would instead produce the "weird" results.

Is that understanding correct?

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See above.