When calling navigator.camera.getPicture with default options except for quality, the requested quality is ignored.
There is a simple work-around, replacing lines 314-315 in CDVCamera.m, :
// use image unedited as requested , don't resize
data = UIImageJPEGRepresentation(returnedImage, 1.0);
// use image unedited as requested , don't resize (with compression)
data = UIImageJPEGRepresentation(returnedImage, cameraPicker.quality / 100.0f);
However, the code hints there may be some (undocumented?) intention to minimize processing in some situations, so this may not be a full fix.