Advanced signal processing technology including steganographic embedding and digital watermarking is described. For an encoded image, detectability measures can be generated including a first detectability measure associated with a synchronization component strength and a second detectability measure associated with a message component strength. Such measures can be used to help determine a likelihood that the encoded image, once printed on a physical substrate, will be detectable from optical scan data representing such. Of course, other features and combinations are described as well.