When Einsteins last simultanous train comes in the station.

The stressing of need for mathematical form in discussing relativity problems attracted my attention..

I have a question regarding Einstein's original moving train gedunken. Perhaps someone can help clear up something for me.

Photons are emitted from A and B in a stationary frame, just as a moving observer M' arrives at M, the midpoint of A and B. M' is heading toward B, away from A. Later a photon from B is detected at M', then a photon from A is detected at M', in the moving frame. SR theory, as I understand, concludes that the photons emitted simultaneously from A and B in the stationaary frame are not emitted simultaneously in the moving frame. I accept that SR pedicts this.

Suppose we included on the moving frame an extension rod stretching a distance A'B' > AB (to account for any shrinking in the moving frame). At each end of the rod is a section of photo-sensitive strips each numbered such that the number 1 strip at one end is equidistant fom M' as is the number 1 strip at the other end of the rod and so on for a few thousand strips in each section. The strip widths are fractions of a micron.

The common midpoint M' for the numbered strips was determined by the same laws of physics that determined the midpoint M of A and B in the stationary frame.

Just as the photons are emitted simultaneously in the stationary frame photons expose a few photo-sensitive strips in each section, at equally distances from M' in the moving frame.

What affect does considering the simultaneous exposure of the photo-sensitve strips in the moving frame have on the logic and physics of applying special relativity postulates that determined the photons were not emitted simultaneously in the moving frame?

I would really appreciate a focus on the specifics of the question as I stipulate the results of applying SR to the problem. SR pedicts as I have stated.