Paulsson:Plate reader

Filters
070715 All our filters (CFP, YFP, and RFP sets on B wheel/slide) oriented according to Chroma recommendations, with arrow on filter-frame oriented toward body of holder (for excitation filters, pointing away from light source; for emission filters, pointing towards specimen).

Protocols
Must measure cellular fluorescence from below. Using 'Top' measurement protocol, cells without fluorescent protein appear significantly less fluorescent than media alone. This problem doesn't occur using 'bottom' measurement.

When measuring from above, reading for cells lacking FP is less than that for media alone?!?! This is a problem because you can't subtract out the contribution of media to the signal before normalizing for OD.