Observer in the double slit experiment with photons In the double slit experiment with photons, the interacting observer is an instrument, detector… 
If you replace the detector with a piece of metal with the same mass as the mass of the detector, the wave will collapse?
 A: In this experiment a changeable detection is designed

Overall, the results suggest that the type of scattering an electron undergoes determines the mark it leaves on the back wall, and that a detector at one of the slits can change the type of scattering. The physicists concluded that, while elastically scattered electrons can cause an interference pattern, the inelastically scattered electrons do not contribute to the interference process.

So, imo,  a double slit experiment with detectors at the slits changes the boundary conditions , whether the detectors are active or not, at least this how  what this more recent experiment can be interpreted.
A: No.  The strange behavior of the photons is directly related to the observation of which slit the photon passes through.  Once it is no longer an observer, and by observer we mean that we detect the presence of a photon, the results change.  The original experiment kept the detector in place and simply did not activate it, so it would have had the same weight of course.
