A photographer friend shoots with two D80's. On the "wrench" menu of one, there are more selections than the other camera, including mirror lock-up for cleaning the sensor. The second camera has NO mirror lockup selection at all (it's not that it's grayed out, it is just missing). Both cameras have fully charged battery, both are set for the same mode/settings otherwise. Why would one be different? Is this a firmware update issue? She'd like to be able to clean the sensor on both of them.