If I understand what you're saying you're wrong, the aperture doesn't change with the 1.6 crop factor, only the focal length. In this case the focal length would be 136mm as you state but the f/stop would remain f/0.85.
JD
But the effect of the f0.85 would be like f1.35 on 1.6x crop. Because the larger sensor allows use of a higher ISO with same noise and shallower DOF, using f1.35 on FF would produce roughly the same result as f0.85 on 1.6x crop.
For example, ISO 3200 at 1.0 on 1.6x crop and ISO 5000 at f1.6 on FF are going to have about the same DOF and Noise. So you really do end up with a crop factor on aperture, too.












