Despite removing the hot mirror of my mirrorless camera (a second-hand EOS M), the required exposure times were significantly longer than what I had anticipated. In my case, a proper exposure at noon required 1/30s at f/2.8, ISO 800. In contrast to that other people online were reporting much shorter exposure times such as 1/125 at f/8, ISO 100; 8 full stops shorter than my own.
It turns out that the dust reduction filter on interchangeable lens systems (i.e. DSLRs and mirrorless) also functions as a secondary IR filter. Thus, I had only removed one out of two filters on the camera.
the hot mirror which was removed
the dust reduction filter which was put back
