I messaged with Robin at SharpCap about the possibility to include 2x1 and 1x2 binning with, for example, the 183MM camera. He told me that this is not possible due to the lack of support for this feature in the ZWO SDK (which only supports binning of the same amount in each direction).
In fact, for spectroscopy experiments (for which many large sensor ZWO cameras are quite good for), having unequal binning is quite useful. The same sampling is often not required in both directions and by binning in one direction, the amount of data though the I/O can be reduced, thereby increasing throughput (e.g. FPS), while preserving high sampling in the other direction.
1x2 and 2x1 binning (or actually, an arbitrary n x m combination) was quite common for CCD cameras used for scientific purposes. As ZWO CMOS cameras are increasingly replacing older CCD ones, I think including the n x m binning feature in the SDK would be a good idea. I suspect it is not very difficult to implement and would likely be welcomed for users of the larger (high pixel count) sensors.
