A solid-state image sensor comprising: a photodiode configured to detect presence or absence of incidence of one photon; a count unit configured to count a number of times a photon has been incident within a predetermined exposure period and output a count value; a count control unit configured to perform control to stop the count unit and perform a request of time information in a case where the count value has reached a predetermined value before the predetermined exposure period elapses; a clock unit configured to measure a time and output the time information in response to the request of time information; and an estimation unit configured to estimate a number of incident times of a photon within the predetermined exposure period on a basis of the output time information, wherein the count control unit is further configured to output the request of time information to the clock unit, and the count unit and the count control unit are arranged in each of a plurality of pixel circuits arrayed in a two-dimensional lattice manner, wherein the predetermined value includes a limit value for limiting the count value and an immediately preceding value indicating the count value before reaching the limit value, the count control unit is further configured to perform control to continuously output the request of time information to the clock unit during a period from when the count value has reached the immediately preceding value to when the count value has reached the limit value and control to stop the count unit when the count value has reached the limit value, the clock unit is further configured to output the time information for each time within the period in which the request of time information is being input to the clock unit, and the estimation unit is further configured to estimate the number of incident times of a photon on a basis of the time information of when the count value has reached the limit value. a photodiode configured to detect presence or absence of incidence of one photon; a count unit configured to count a number of times a photon has been incident within a predetermined exposure period and output a count value; a count control unit configured to perform control to stop the count unit and perform a request of time information in a case where the count value has reached a predetermined value before the predetermined exposure period elapses; a clock unit configured to measure a time and output the time information in response to the request of time information; and an estimation unit configured to estimate a number of incident times of a photon within the predetermined exposure period on a basis of the output time information, wherein the count control unit is further configured to output the request of time information to the clock unit, and the count unit and the count control unit are arranged in each of a plurality of pixel circuits arrayed in a two-dimensional lattice manner, wherein the predetermined value includes a limit value for limiting the count value and an immediately preceding value indicating the count value before reaching the limit value, the count control unit is further configured to perform control to continuously output the request of time information to the clock unit during a period from when the count value has reached the immediately preceding value to when the count value has reached the limit value and control to stop the count unit when the count value has reached the limit value, the clock unit is further configured to output the time information for each time within the period in which the request of time information is being input to the clock unit, and the estimation unit is further configured to estimate the number of incident times of a photon on a basis of the time information of when the count value has reached the limit value.