Capture mode depends upon the Timer1 module for proper operation. Two of the Timer1 clock source options will work with the Capture mode: the Fosc/4 instruction clock and the external clock option. Each clock source has a different effect on Capture mode during sleep.
If Timer1 is driven by the instruction clock (FOSC/4), Timer1 will not increment during sleep. This means that the Capture mode will not work during sleep. When the device wakes from sleep, Timer1 will continue from its previous state.
If Timer1 is driven by an external clock, then Timer1 will continue to increment in sleep mode and Capture mode will also operate during Sleep.