YAGNI? :) I'm fine with adding something that parses a string input to get the bit-depth (or adding some alternate input syntax), but I'm not really sure it's necessary. These three special cases were added because many cameras produce 10, 12, and 14 bit images (e.g. high-speed cameras and other scientific cameras). It wouldn't be a bad idea to add uint32 and uint64 for the normal dtype-range (i.e. the one defined in the `util.dtype`) for completeness (some work may need be necessary to get these dtypes working with `convert`, though).